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 :-) >>>> >>> >>> >> >
