Re: [pygame] trajectory
Thanks. The TD i have planned to code may contain lot of direction changes so i think i will use homing missile, i have already started to code a kind of homing missile firing system using vector thanks to numpy and it s not too bad. Le 25 juil. 2011 à 06:07, Jake b ninmonk...@gmail.com a écrit This calculates to shoot in the path of the target. Like how you throw a football, to lead the catcher. Instead of where they are at that second. For tower defense, some Bullets fly fast enough you don't have to lead. Slower bullets fire, then every frame you: Move the bullet location toward target. ( without leading ) Thats simple homing, but you can skip the steering part a homing missile has. The trajectory will end up curving, depending on speeds used. For a straight line you will have to lead. But leading will miss if target chamges direction or speed. On Saturday, July 23, 2011, Joe Ranalli jrana...@gmail.com wrote: Yes. So to be more explicit: 1 Calculate the distance between the source and the target. 2 Calculate the time for the bullet to move that distance (i.e. by dividing this distance by the bullet velocity) 3 Calculate newposition (multiply the target velocity by the time calculated in the previous step, add to original target position) 1a Recalculate the distance between the source and newposition 2a Recalculate the time for the bullet to move from the source to newposition (i.e. divide the new distance by the bullet velocity) 3a Recalculate newposition using this new time (multiply the target velocity by the new time calculated in the previous step, add to original target position) On Sat, Jul 23, 2011 at 12:55 PM, Nathan BIAGINI nathan.o...@gmail.com wrote: Ok so thanks all for all your replies i will work with all that. I don't know already if i want to use homing missile style which seems to be easier to code or to use an algorithm to fire straight to the right spot. To be honest, i'm not native english speaker and it's not always easy to figure out what you really mean but i'm doing my best. I just want to ask you Joe about your algorithm : If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Ok so i think the first step is pretty clear to me, the step 2 too but i don't understand the step 3. My english isn't the best i repeat so... i have to calculate how long the bullet will take to go to 'newposition'. So i will get a new time value and then i need to recalculate newposition based on this new time? And fire at 'newposition'? And also, to be sure, 'newposition' is the virtual position of the target after the time taken by the bullet to hit it, right? Sorry if it seems to be straigh forward to you :-) Of course i will try others way like Lee suggested me. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.com wrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-) -- Jake
Re: [pygame] trajectory
Im late to this threath but Why dont recalculate de vector in each iteration? they are two substractions... not a extensive calculation... no? This way missile ALWAYS will reach it objetive. 2011/7/25 BIAGINI Nathan nathan.o...@gmail.com: Thanks. The TD i have planned to code may contain lot of direction changes so i think i will use homing missile, i have already started to code a kind of homing missile firing system using vector thanks to numpy and it s not too bad. Le 25 juil. 2011 à 06:07, Jake b ninmonk...@gmail.com a écrit This calculates to shoot in the path of the target. Like how you throw a football, to lead the catcher. Instead of where they are at that second. For tower defense, some Bullets fly fast enough you don't have to lead. Slower bullets fire, then every frame you: Move the bullet location toward target. ( without leading ) Thats simple homing, but you can skip the steering part a homing missile has. The trajectory will end up curving, depending on speeds used. For a straight line you will have to lead. But leading will miss if target chamges direction or speed. On Saturday, July 23, 2011, Joe Ranalli jrana...@gmail.com wrote: Yes. So to be more explicit: 1 Calculate the distance between the source and the target. 2 Calculate the time for the bullet to move that distance (i.e. by dividing this distance by the bullet velocity) 3 Calculate newposition (multiply the target velocity by the time calculated in the previous step, add to original target position) 1a Recalculate the distance between the source and newposition 2a Recalculate the time for the bullet to move from the source to newposition (i.e. divide the new distance by the bullet velocity) 3a Recalculate newposition using this new time (multiply the target velocity by the new time calculated in the previous step, add to original target position) On Sat, Jul 23, 2011 at 12:55 PM, Nathan BIAGINI nathan.o...@gmail.com wrote: Ok so thanks all for all your replies i will work with all that. I don't know already if i want to use homing missile style which seems to be easier to code or to use an algorithm to fire straight to the right spot. To be honest, i'm not native english speaker and it's not always easy to figure out what you really mean but i'm doing my best. I just want to ask you Joe about your algorithm : If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Ok so i think the first step is pretty clear to me, the step 2 too but i don't understand the step 3. My english isn't the best i repeat so... i have to calculate how long the bullet will take to go to 'newposition'. So i will get a new time value and then i need to recalculate newposition based on this new time? And fire at 'newposition'? And also, to be sure, 'newposition' is the virtual position of the target after the time taken by the bullet to hit it, right? Sorry if it seems to be straigh forward to you :-) Of course i will try others way like Lee suggested me. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.com wrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance
Re: [pygame] trajectory
This calculates to shoot in the path of the target. Like how you throw a football, to lead the catcher. Instead of where they are at that second. For tower defense, some Bullets fly fast enough you don't have to lead. Slower bullets fire, then every frame you: Move the bullet location toward target. ( without leading ) Thats simple homing, but you can skip the steering part a homing missile has. The trajectory will end up curving, depending on speeds used. For a straight line you will have to lead. But leading will miss if target chamges direction or speed. On Saturday, July 23, 2011, Joe Ranalli jrana...@gmail.com wrote: Yes. So to be more explicit: 1 Calculate the distance between the source and the target. 2 Calculate the time for the bullet to move that distance (i.e. by dividing this distance by the bullet velocity) 3 Calculate newposition (multiply the target velocity by the time calculated in the previous step, add to original target position) 1a Recalculate the distance between the source and newposition 2a Recalculate the time for the bullet to move from the source to newposition (i.e. divide the new distance by the bullet velocity) 3a Recalculate newposition using this new time (multiply the target velocity by the new time calculated in the previous step, add to original target position) On Sat, Jul 23, 2011 at 12:55 PM, Nathan BIAGINI nathan.o...@gmail.com wrote: Ok so thanks all for all your replies i will work with all that. I don't know already if i want to use homing missile style which seems to be easier to code or to use an algorithm to fire straight to the right spot. To be honest, i'm not native english speaker and it's not always easy to figure out what you really mean but i'm doing my best. I just want to ask you Joe about your algorithm : If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Ok so i think the first step is pretty clear to me, the step 2 too but i don't understand the step 3. My english isn't the best i repeat so... i have to calculate how long the bullet will take to go to 'newposition'. So i will get a new time value and then i need to recalculate newposition based on this new time? And fire at 'newposition'? And also, to be sure, 'newposition' is the virtual position of the target after the time taken by the bullet to hit it, right? Sorry if it seems to be straigh forward to you :-) Of course i will try others way like Lee suggested me. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.com wrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-) -- Jake
Re: [pygame] trajectory
Ok so thanks all for all your replies i will work with all that. I don't know already if i want to use homing missile style which seems to be easier to code or to use an algorithm to fire straight to the right spot. To be honest, i'm not native english speaker and it's not always easy to figure out what you really mean but i'm doing my best. I just want to ask you Joe about your algorithm : If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Ok so i think the first step is pretty clear to me, the step 2 too but i don't understand the step 3. My english isn't the best i repeat so... i have to calculate how long the bullet will take to go to 'newposition'. So i will get a new time value and then i need to recalculate newposition based on this new time? And fire at 'newposition'? And also, to be sure, 'newposition' is the virtual position of the target after the time taken by the bullet to hit it, right? Sorry if it seems to be straigh forward to you :-) Of course i will try others way like Lee suggested me. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
Ok. Yeah it's more explicit, thanks to take time to rewrite it. So it will works in case of re
Re: [pygame] trajectory
Ok. Yeah it's more explicit, thanks to take time to rewrite it. So it will works in case of really simple tower defense graph, where the target always progress to a point A to a point B? 2011/7/23 Joe Ranalli jrana...@gmail.com Yes. So to be more explicit: 1 Calculate the distance between the source and the target. 2 Calculate the time for the bullet to move that distance (i.e. by dividing this distance by the bullet velocity) 3 Calculate newposition (multiply the target velocity by the time calculated in the previous step, add to original target position) 1a Recalculate the distance between the source and newposition 2a Recalculate the time for the bullet to move from the source to newposition (i.e. divide the new distance by the bullet velocity) 3a Recalculate newposition using this new time (multiply the target velocity by the new time calculated in the previous step, add to original target position) On Sat, Jul 23, 2011 at 12:55 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: Ok so thanks all for all your replies i will work with all that. I don't know already if i want to use homing missile style which seems to be easier to code or to use an algorithm to fire straight to the right spot. To be honest, i'm not native english speaker and it's not always easy to figure out what you really mean but i'm doing my best. I just want to ask you Joe about your algorithm : If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Ok so i think the first step is pretty clear to me, the step 2 too but i don't understand the step 3. My english isn't the best i repeat so... i have to calculate how long the bullet will take to go to 'newposition'. So i will get a new time value and then i need to recalculate newposition based on this new time? And fire at 'newposition'? And also, to be sure, 'newposition' is the virtual position of the target after the time taken by the bullet to hit it, right? Sorry if it seems to be straigh forward to you :-) Of course i will try others way like Lee suggested me. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
Yes, it will work as long as the target doesn't change direction. On Sat, Jul 23, 2011 at 1:13 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: Ok. Yeah it's more explicit, thanks to take time to rewrite it. So it will works in case of really simple tower defense graph, where the target always progress to a point A to a point B? 2011/7/23 Joe Ranalli jrana...@gmail.com Yes. So to be more explicit: 1 Calculate the distance between the source and the target. 2 Calculate the time for the bullet to move that distance (i.e. by dividing this distance by the bullet velocity) 3 Calculate newposition (multiply the target velocity by the time calculated in the previous step, add to original target position) 1a Recalculate the distance between the source and newposition 2a Recalculate the time for the bullet to move from the source to newposition (i.e. divide the new distance by the bullet velocity) 3a Recalculate newposition using this new time (multiply the target velocity by the new time calculated in the previous step, add to original target position) On Sat, Jul 23, 2011 at 12:55 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: Ok so thanks all for all your replies i will work with all that. I don't know already if i want to use homing missile style which seems to be easier to code or to use an algorithm to fire straight to the right spot. To be honest, i'm not native english speaker and it's not always easy to figure out what you really mean but i'm doing my best. I just want to ask you Joe about your algorithm : If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Ok so i think the first step is pretty clear to me, the step 2 too but i don't understand the step 3. My english isn't the best i repeat so... i have to calculate how long the bullet will take to go to 'newposition'. So i will get a new time value and then i need to recalculate newposition based on this new time? And fire at 'newposition'? And also, to be sure, 'newposition' is the virtual position of the target after the time taken by the bullet to hit it, right? Sorry if it seems to be straigh forward to you :-) Of course i will try others way like Lee suggested me. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
So if the source if moving to the left, get in range of a tower and during the algorithm progress go up or down, it will not work. That's it? 2011/7/23 Joe Ranalli jrana...@gmail.com Yes, it will work as long as the target doesn't change direction. On Sat, Jul 23, 2011 at 1:13 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: Ok. Yeah it's more explicit, thanks to take time to rewrite it. So it will works in case of really simple tower defense graph, where the target always progress to a point A to a point B? 2011/7/23 Joe Ranalli jrana...@gmail.com Yes. So to be more explicit: 1 Calculate the distance between the source and the target. 2 Calculate the time for the bullet to move that distance (i.e. by dividing this distance by the bullet velocity) 3 Calculate newposition (multiply the target velocity by the time calculated in the previous step, add to original target position) 1a Recalculate the distance between the source and newposition 2a Recalculate the time for the bullet to move from the source to newposition (i.e. divide the new distance by the bullet velocity) 3a Recalculate newposition using this new time (multiply the target velocity by the new time calculated in the previous step, add to original target position) On Sat, Jul 23, 2011 at 12:55 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: Ok so thanks all for all your replies i will work with all that. I don't know already if i want to use homing missile style which seems to be easier to code or to use an algorithm to fire straight to the right spot. To be honest, i'm not native english speaker and it's not always easy to figure out what you really mean but i'm doing my best. I just want to ask you Joe about your algorithm : If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Ok so i think the first step is pretty clear to me, the step 2 too but i don't understand the step 3. My english isn't the best i repeat so... i have to calculate how long the bullet will take to go to 'newposition'. So i will get a new time value and then i need to recalculate newposition based on this new time? And fire at 'newposition'? And also, to be sure, 'newposition' is the virtual position of the target after the time taken by the bullet to hit it, right? Sorry if it seems to be straigh forward to you :-) Of course i will try others way like Lee suggested me. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.com wrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
You are aiming the bullet based on where you calculate the target will be when the bullet gets there. If the target changes direction, your aim is wrong. On Sat, Jul 23, 2011 at 1:24 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: So if the source if moving to the left, get in range of a tower and during the algorithm progress go up or down, it will not work. That's it? 2011/7/23 Joe Ranalli jrana...@gmail.com Yes, it will work as long as the target doesn't change direction. On Sat, Jul 23, 2011 at 1:13 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: Ok. Yeah it's more explicit, thanks to take time to rewrite it. So it will works in case of really simple tower defense graph, where the target always progress to a point A to a point B? 2011/7/23 Joe Ranalli jrana...@gmail.com Yes. So to be more explicit: 1 Calculate the distance between the source and the target. 2 Calculate the time for the bullet to move that distance (i.e. by dividing this distance by the bullet velocity) 3 Calculate newposition (multiply the target velocity by the time calculated in the previous step, add to original target position) 1a Recalculate the distance between the source and newposition 2a Recalculate the time for the bullet to move from the source to newposition (i.e. divide the new distance by the bullet velocity) 3a Recalculate newposition using this new time (multiply the target velocity by the new time calculated in the previous step, add to original target position) On Sat, Jul 23, 2011 at 12:55 PM, Nathan BIAGINI nathan.o...@gmail.com wrote: Ok so thanks all for all your replies i will work with all that. I don't know already if i want to use homing missile style which seems to be easier to code or to use an algorithm to fire straight to the right spot. To be honest, i'm not native english speaker and it's not always easy to figure out what you really mean but i'm doing my best. I just want to ask you Joe about your algorithm : If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Ok so i think the first step is pretty clear to me, the step 2 too but i don't understand the step 3. My english isn't the best i repeat so... i have to calculate how long the bullet will take to go to 'newposition'. So i will get a new time value and then i need to recalculate newposition based on this new time? And fire at 'newposition'? And also, to be sure, 'newposition' is the virtual position of the target after the time taken by the bullet to hit it, right? Sorry if it seems to be straigh forward to you :-) Of course i will try others way like Lee suggested me. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.com wrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
Yeah but if you calculate the node of the graph where the target will be when the bullet get there. Can it works? 2011/7/23 Joe Ranalli jrana...@gmail.com You are aiming the bullet based on where you calculate the target will be when the bullet gets there. If the target changes direction, your aim is wrong. On Sat, Jul 23, 2011 at 1:24 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: So if the source if moving to the left, get in range of a tower and during the algorithm progress go up or down, it will not work. That's it? 2011/7/23 Joe Ranalli jrana...@gmail.com Yes, it will work as long as the target doesn't change direction. On Sat, Jul 23, 2011 at 1:13 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: Ok. Yeah it's more explicit, thanks to take time to rewrite it. So it will works in case of really simple tower defense graph, where the target always progress to a point A to a point B? 2011/7/23 Joe Ranalli jrana...@gmail.com Yes. So to be more explicit: 1 Calculate the distance between the source and the target. 2 Calculate the time for the bullet to move that distance (i.e. by dividing this distance by the bullet velocity) 3 Calculate newposition (multiply the target velocity by the time calculated in the previous step, add to original target position) 1a Recalculate the distance between the source and newposition 2a Recalculate the time for the bullet to move from the source to newposition (i.e. divide the new distance by the bullet velocity) 3a Recalculate newposition using this new time (multiply the target velocity by the new time calculated in the previous step, add to original target position) On Sat, Jul 23, 2011 at 12:55 PM, Nathan BIAGINI nathan.o...@gmail.com wrote: Ok so thanks all for all your replies i will work with all that. I don't know already if i want to use homing missile style which seems to be easier to code or to use an algorithm to fire straight to the right spot. To be honest, i'm not native english speaker and it's not always easy to figure out what you really mean but i'm doing my best. I just want to ask you Joe about your algorithm : If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Ok so i think the first step is pretty clear to me, the step 2 too but i don't understand the step 3. My english isn't the best i repeat so... i have to calculate how long the bullet will take to go to 'newposition'. So i will get a new time value and then i need to recalculate newposition based on this new time? And fire at 'newposition'? And also, to be sure, 'newposition' is the virtual position of the target after the time taken by the bullet to hit it, right? Sorry if it seems to be straigh forward to you :-) Of course i will try others way like Lee suggested me. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.com wrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
Oh, sure. If you know exactly how the target will move and calculate newposition based on where the target will be including changes of direction and everything, then you will be aiming at the right spot. It still seems like using the homing bullets would be easier though. On Sat, Jul 23, 2011 at 1:29 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: Yeah but if you calculate the node of the graph where the target will be when the bullet get there. Can it works? 2011/7/23 Joe Ranalli jrana...@gmail.com You are aiming the bullet based on where you calculate the target will be when the bullet gets there. If the target changes direction, your aim is wrong. On Sat, Jul 23, 2011 at 1:24 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: So if the source if moving to the left, get in range of a tower and during the algorithm progress go up or down, it will not work. That's it? 2011/7/23 Joe Ranalli jrana...@gmail.com Yes, it will work as long as the target doesn't change direction. On Sat, Jul 23, 2011 at 1:13 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: Ok. Yeah it's more explicit, thanks to take time to rewrite it. So it will works in case of really simple tower defense graph, where the target always progress to a point A to a point B? 2011/7/23 Joe Ranalli jrana...@gmail.com Yes. So to be more explicit: 1 Calculate the distance between the source and the target. 2 Calculate the time for the bullet to move that distance (i.e. by dividing this distance by the bullet velocity) 3 Calculate newposition (multiply the target velocity by the time calculated in the previous step, add to original target position) 1a Recalculate the distance between the source and newposition 2a Recalculate the time for the bullet to move from the source to newposition (i.e. divide the new distance by the bullet velocity) 3a Recalculate newposition using this new time (multiply the target velocity by the new time calculated in the previous step, add to original target position) On Sat, Jul 23, 2011 at 12:55 PM, Nathan BIAGINI nathan.o...@gmail.com wrote: Ok so thanks all for all your replies i will work with all that. I don't know already if i want to use homing missile style which seems to be easier to code or to use an algorithm to fire straight to the right spot. To be honest, i'm not native english speaker and it's not always easy to figure out what you really mean but i'm doing my best. I just want to ask you Joe about your algorithm : If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Ok so i think the first step is pretty clear to me, the step 2 too but i don't understand the step 3. My english isn't the best i repeat so... i have to calculate how long the bullet will take to go to 'newposition'. So i will get a new time value and then i need to recalculate newposition based on this new time? And fire at 'newposition'? And also, to be sure, 'newposition' is the virtual position of the target after the time taken by the bullet to hit it, right? Sorry if it seems to be straigh forward to you :-) Of course i will try others way like Lee suggested me. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.com wrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create
Re: [pygame] trajectory
Yeah i also think so... and if the bullet is really faster than the target, it should not be that much visible. 2011/7/23 Joe Ranalli jrana...@gmail.com Oh, sure. If you know exactly how the target will move and calculate newposition based on where the target will be including changes of direction and everything, then you will be aiming at the right spot. It still seems like using the homing bullets would be easier though. On Sat, Jul 23, 2011 at 1:29 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: Yeah but if you calculate the node of the graph where the target will be when the bullet get there. Can it works? 2011/7/23 Joe Ranalli jrana...@gmail.com You are aiming the bullet based on where you calculate the target will be when the bullet gets there. If the target changes direction, your aim is wrong. On Sat, Jul 23, 2011 at 1:24 PM, Nathan BIAGINI nathan.o...@gmail.comwrote: So if the source if moving to the left, get in range of a tower and during the algorithm progress go up or down, it will not work. That's it? 2011/7/23 Joe Ranalli jrana...@gmail.com Yes, it will work as long as the target doesn't change direction. On Sat, Jul 23, 2011 at 1:13 PM, Nathan BIAGINI nathan.o...@gmail.com wrote: Ok. Yeah it's more explicit, thanks to take time to rewrite it. So it will works in case of really simple tower defense graph, where the target always progress to a point A to a point B? 2011/7/23 Joe Ranalli jrana...@gmail.com Yes. So to be more explicit: 1 Calculate the distance between the source and the target. 2 Calculate the time for the bullet to move that distance (i.e. by dividing this distance by the bullet velocity) 3 Calculate newposition (multiply the target velocity by the time calculated in the previous step, add to original target position) 1a Recalculate the distance between the source and newposition 2a Recalculate the time for the bullet to move from the source to newposition (i.e. divide the new distance by the bullet velocity) 3a Recalculate newposition using this new time (multiply the target velocity by the new time calculated in the previous step, add to original target position) On Sat, Jul 23, 2011 at 12:55 PM, Nathan BIAGINI nathan.o...@gmail.com wrote: Ok so thanks all for all your replies i will work with all that. I don't know already if i want to use homing missile style which seems to be easier to code or to use an algorithm to fire straight to the right spot. To be honest, i'm not native english speaker and it's not always easy to figure out what you really mean but i'm doing my best. I just want to ask you Joe about your algorithm : If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Ok so i think the first step is pretty clear to me, the step 2 too but i don't understand the step 3. My english isn't the best i repeat so... i have to calculate how long the bullet will take to go to 'newposition'. So i will get a new time value and then i need to recalculate newposition based on this new time? And fire at 'newposition'? And also, to be sure, 'newposition' is the virtual position of the target after the time taken by the bullet to hit it, right? Sorry if it seems to be straigh forward to you :-) Of course i will try others way like Lee suggested me. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.com wrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a
Re: [pygame] trajectory
i would like to know what are the common way to handle trajectory in a 2d game. http://hyperphysics.phy-astr.gsu.edu/hbase/traj.html
Re: [pygame] trajectory
Hi. Thanks all for you replies i have one more question before trying to write something on top of that, your algorithme Joe, does it works if the way has some bifurcations, i mean, a fully linear way but that contain bifurcations. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
I'm not totally clear on what you're asking. If you're saying that the targets might change direction after the bullet is fired, but you still want the bullet to hit the target, then my second algorithm wouldn't work. That just doesn't make any sense. The algorithm I suggested aims at the target, then shoots at it. If the target changes direction, then it will no longer go to the spot you were aiming. If you're having this much trouble figuring this out I would definitely suggest you take some time to sit down and think about what it is you're trying to do and maybe read about some simple physics. This part of the application really shouldn't be that difficult to figure out. On Fri, Jul 22, 2011 at 9:08 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Hi. Thanks all for you replies i have one more question before trying to write something on top of that, your algorithme Joe, does it works if the way has some bifurcations, i mean, a fully linear way but that contain bifurcations. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
Unless the bullet can change direction in flight, it will have to choose one, and only one spot to aim for, and therefore, one vector to guide it. Homing missiles are a lot different to code for, since they have to adjust course, and potentially deal with a synthesized form of inertia. A bifurcating tree of solutions seems to suggest looking at all possible 'likely' positions for the target in the future. That's not so much vector math as it is statistics and player-psychology. You also probably don't want to deal with linear solutions to this problem, unless you really really need pinpoint accuracy on each shot (again, assuming NOTHING changes direction or speed after a shot is fired, which makes all that accuracy useless anyway). Breaking it up into steps that are a little smaller than the clipping rectangles involved will probably get you more than close enough. Furthermore, there will be a different solution to the linear form of the problem for every firing angle (wide angles intercept later, etc...) It would get pretty ugly. It might suit better to 'fudge' in a calculation. Make an estimated change (just add a constant or something) to the current position of the target, based on it's speed and direction, and fire at that position. Divide the x and y distance to the target each by the speed of your bullet (you don't even NEED to do the trigonometry for speed calculations, the player wouldn't notice much anyway) and make the bullet move that much in the x and y directions each tick. Try it out... are your shots firing too far ahead? Too far behind?? Change the estimation constant a little bit and try again. If the target is in close, you might have to reduce the estimate a bit, etc... You can probably tweak this one enough to have a very satisfying firing computer without having to go through the hassle of reading the physics chapter on ballistics. Just a few ideas... -Lee- On Fri, Jul 22, 2011 at 7:21 AM, Joe Ranalli jrana...@gmail.com wrote: I'm not totally clear on what you're asking. If you're saying that the targets might change direction after the bullet is fired, but you still want the bullet to hit the target, then my second algorithm wouldn't work. That just doesn't make any sense. The algorithm I suggested aims at the target, then shoots at it. If the target changes direction, then it will no longer go to the spot you were aiming. If you're having this much trouble figuring this out I would definitely suggest you take some time to sit down and think about what it is you're trying to do and maybe read about some simple physics. This part of the application really shouldn't be that difficult to figure out. On Fri, Jul 22, 2011 at 9:08 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Hi. Thanks all for you replies i have one more question before trying to write something on top of that, your algorithme Joe, does it works if the way has some bifurcations, i mean, a fully linear way but that contain bifurcations. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
In most (but maybe not all) tower defense games I have ever played, bullets *can* change direction in flight, and do behave like homing missles. This isn't obvious visually if the bullets are fast, but it is pretty common in tower defense games that if a target is in range when the bullet is launched that it will always hit the target no matter how it moves. That being said, I don't have any idea if Nathan Biagini wants to make his own tower defense game work that way or not :) --- James Paige On Fri, Jul 22, 2011 at 08:24:51AM -0700, Lee Buckingham wrote: Unless the bullet can change direction in flight, it will have to choose one, and only one spot to aim for, and therefore, one vector to guide it. Homing missiles are a lot different to code for, since they have to adjust course, and potentially deal with a synthesized form of inertia. A bifurcating tree of solutions seems to suggest looking at all possible 'likely' positions for the target in the future. That's not so much vector math as it is statistics and player-psychology. You also probably don't want to deal with linear solutions to this problem, unless you really really need pinpoint accuracy on each shot (again, assuming NOTHING changes direction or speed after a shot is fired, which makes all that accuracy useless anyway). Breaking it up into steps that are a little smaller than the clipping rectangles involved will probably get you more than close enough. Furthermore, there will be a different solution to the linear form of the problem for every firing angle (wide angles intercept later, etc...) It would get pretty ugly. It might suit better to 'fudge' in a calculation. Make an estimated change (just add a constant or something) to the current position of the target, based on it's speed and direction, and fire at that position. Divide the x and y distance to the target each by the speed of your bullet (you don't even NEED to do the trigonometry for speed calculations, the player wouldn't notice much anyway) and make the bullet move that much in the x and y directions each tick. Try it out... are your shots firing too far ahead? Too far behind?? Change the estimation constant a little bit and try again. If the target is in close, you might have to reduce the estimate a bit, etc... You can probably tweak this one enough to have a very satisfying firing computer without having to go through the hassle of reading the physics chapter on ballistics. Just a few ideas... -Lee- On Fri, Jul 22, 2011 at 7:21 AM, Joe Ranalli jrana...@gmail.com wrote: I'm not totally clear on what you're asking. If you're saying that the targets might change direction after the bullet is fired, but you still want the bullet to hit the target, then my second algorithm wouldn't work. That just doesn't make any sense. The algorithm I suggested aims at the target, then shoots at it. If the target changes direction, then it will no longer go to the spot you were aiming. If you're having this much trouble figuring this out I would definitely suggest you take some time to sit down and think about what it is you're trying to do and maybe read about some simple physics. This part of the application really shouldn't be that difficult to figure out. On Fri, Jul 22, 2011 at 9:08 AM, Nathan BIAGINI nathan.o...@gmail.com wrote: Hi. Thanks all for you replies i have one more question before trying to write something on top of that, your algorithme Joe, does it works if the way has some bifurcations, i mean, a fully linear way but that contain bifurcations. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could
Re: [pygame] trajectory
Homing missile is by far the easiest thing to code. Every clock tick, find the vector between the bullet and the target, move the bullet in that direction according to its velocity. As long as the bullet speed is fast relative to the target, it will eventually hit it. On Fri, Jul 22, 2011 at 11:56 AM, James Paige b...@hamsterrepublic.comwrote: In most (but maybe not all) tower defense games I have ever played, bullets *can* change direction in flight, and do behave like homing missles. This isn't obvious visually if the bullets are fast, but it is pretty common in tower defense games that if a target is in range when the bullet is launched that it will always hit the target no matter how it moves. That being said, I don't have any idea if Nathan Biagini wants to make his own tower defense game work that way or not :) --- James Paige On Fri, Jul 22, 2011 at 08:24:51AM -0700, Lee Buckingham wrote: Unless the bullet can change direction in flight, it will have to choose one, and only one spot to aim for, and therefore, one vector to guide it. Homing missiles are a lot different to code for, since they have to adjust course, and potentially deal with a synthesized form of inertia. A bifurcating tree of solutions seems to suggest looking at all possible 'likely' positions for the target in the future. That's not so much vector math as it is statistics and player-psychology. You also probably don't want to deal with linear solutions to this problem, unless you really really need pinpoint accuracy on each shot (again, assuming NOTHING changes direction or speed after a shot is fired, which makes all that accuracy useless anyway). Breaking it up into steps that are a little smaller than the clipping rectangles involved will probably get you more than close enough. Furthermore, there will be a different solution to the linear form of the problem for every firing angle (wide angles intercept later, etc...) It would get pretty ugly. It might suit better to 'fudge' in a calculation. Make an estimated change (just add a constant or something) to the current position of the target, based on it's speed and direction, and fire at that position. Divide the x and y distance to the target each by the speed of your bullet (you don't even NEED to do the trigonometry for speed calculations, the player wouldn't notice much anyway) and make the bullet move that much in the x and y directions each tick. Try it out... are your shots firing too far ahead? Too far behind?? Change the estimation constant a little bit and try again. If the target is in close, you might have to reduce the estimate a bit, etc... You can probably tweak this one enough to have a very satisfying firing computer without having to go through the hassle of reading the physics chapter on ballistics. Just a few ideas... -Lee- On Fri, Jul 22, 2011 at 7:21 AM, Joe Ranalli jrana...@gmail.com wrote: I'm not totally clear on what you're asking. If you're saying that the targets might change direction after the bullet is fired, but you still want the bullet to hit the target, then my second algorithm wouldn't work. That just doesn't make any sense. The algorithm I suggested aims at the target, then shoots at it. If the target changes direction, then it will no longer go to the spot you were aiming. If you're having this much trouble figuring this out I would definitely suggest you take some time to sit down and think about what it is you're trying to do and maybe read about some simple physics. This part of the application really shouldn't be that difficult to figure out. On Fri, Jul 22, 2011 at 9:08 AM, Nathan BIAGINI nathan.o...@gmail.com wrote: Hi. Thanks all for you replies i have one more question before trying to write something on top of that, your algorithme Joe, does it works if the way has some bifurcations, i mean, a fully linear way but that contain bifurcations. Thanks. 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc
Re: [pygame] trajectory
A more involved example, but a great site is red3d's steering movements. To do heat seeking missiles, you use the seek behavior. http://www.red3d.com/cwr/steer/ On Fri, Jul 22, 2011 at 11:45 AM, Joe Ranalli jrana...@gmail.com wrote: Homing missile is by far the easiest thing to code. Every clock tick, find the vector between the bullet and the target, move the bullet in that direction according to its velocity. As long as the bullet speed is fast relative to the target, it will eventually hit it. -- Jake
[pygame] trajectory
Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
Ok. But all the calcul of how long the bullet will take to reach the target etc... will be made byn using vector? I mean, using a vector still viable? 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
Yes a vector is probably appropriate. On Wed, Jul 20, 2011 at 10:20 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Ok. But all the calcul of how long the bullet will take to reach the target etc... will be made byn using vector? I mean, using a vector still viable? 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
There is a pygame object to create a 2d vector? 2011/7/20 Joe Ranalli jrana...@gmail.com Yes a vector is probably appropriate. On Wed, Jul 20, 2011 at 10:20 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Ok. But all the calcul of how long the bullet will take to reach the target etc... will be made byn using vector? I mean, using a vector still viable? 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
No, but what you're talking about doing isn't hard. If you're having trouble with it, you'll need to look into some elementary physics and trigonometry. On Wed, Jul 20, 2011 at 10:33 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: There is a pygame object to create a 2d vector? 2011/7/20 Joe Ranalli jrana...@gmail.com Yes a vector is probably appropriate. On Wed, Jul 20, 2011 at 10:20 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Ok. But all the calcul of how long the bullet will take to reach the target etc... will be made byn using vector? I mean, using a vector still viable? 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
Not built into pygame, but there is a good one on the pygame wiki: http://pygame.org/wiki/2DVectorClass On Wed, Jul 20, 2011 at 04:33:16PM +0200, Nathan BIAGINI wrote: There is a pygame object to create a 2d vector? 2011/7/20 Joe Ranalli jrana...@gmail.com Yes a vector is probably appropriate. On Wed, Jul 20, 2011 at 10:20 AM, Nathan BIAGINI nathan.o...@gmail.com wrote: Ok. But all the calcul of how long the bullet will take to reach the target etc... will be made byn using vector? I mean, using a vector still viable? 2011/7/20 Joe Ranalli jrana...@gmail.com It depends what you're trying to do. If you draw the straight line between the tower and the enemy and use that vector to translate a bullet each tick, the bullets might miss the enemy. Think about it this way, the bullet moves 2 steps toward the enemy, then the enemy moves 1 step, then the bullet moves 2, etc. Because the enemy moves the bullet will have to change its direction through the flight. So you could calculate the direction vector between the bullet and the enemy every tick and have the bullet move that direction. That would make the bullets kind of arc to the target. If you want to have the bullet go straight to the right spot, you need to: 1) calculate how long the bullet will take to get to the enemy 2) calculate where the enemy will be at that time (newposition) 3) calculate how long it will take the bullet to get to newposition 4) recalculate newposition based on the new time Technically you could iterate that repeatedly until newposition converges. Practically, iterating once probably gets you close enough unless the movement is extremely complicated. On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI nathan.o...@gmail.com wrote: Hi everyone, i would like to know what are the common way to handle trajectory in a 2d game. In fact, i think of writing a tower defense game and i wonder how to handle the trajectory of the missile launch by the towers. I though of getting the pos of the tower and the target and create a vector between this two entitites to make a sprite translation of this vector but there is maybe some tricky stuff to do it. Thanks in advance and happy game making all :-)
Re: [pygame] trajectory
You can define bullet speed in pixels per second. You can use euclid (it works), but I instead suggest numpy. Which has a vector( numpy.array ), and is useful for other game related things. Here's a stand-alone example, uses numpy for vector movement. https://code.google.com/p/ninmonkey/source/browse/boilerplate/pygame/4.%20with%20numpy%20for%20array/boilerplate%20-%20pygame_with_numpy-2011_jake.py On Wed, Jul 20, 2011 at 9:33 AM, Nathan BIAGINI nathan.o...@gmail.comwrote: There is a pygame object to create a 2d vector? -- Jake
