On 03/15/2011 05:03 PM, Doriano Blengino wrote: > Kevin Fishburne ha scritto: >> Just to be clear on what -should- be happening, here's an example. >> Player is facing up (0 degrees): left stick pushed up moves up, pushed >> down >> moves down, pushed left moves left, pushed right moves right. >> Player is facing right (90 degrees): left stick pushed up moves right, >> pushed down moves left, pushed left moves up, pushed right moves down. >> > Well, you need to rotate the data from the left joystick around the > player. This is the formula of rotation: > xr := xp*g92cos - yp*g92sin; > yr := xp*g92sin + yp*g92cos; > > Sorry, I took them from an old pascal program, but I explain. > The above code rotates a point (xp; yp) around the origin, by a given > angle "g92", of which g92cos and g92sin are the cosine and sine. The new > rotated point is (xr; yr). Please note that 0 degrees is toward right, > 90° up, 180 left, but a computer screen is flipped up side down (which > is not a rotation but a mirror), so the y coordinates must be mirrored > (choose the opposite sign if a coordinate is relative, or subtract the > coordinate from the maximum Y coordinate if absolute). In addition, you > say that 0° is up, and 90° right, which is both mirrored and rotated in > respect to the canonical trigonometry... this kind of things can drive > me crazy... :-) > > Back to the problem. If I well understand, at every frame you take the > left joystick, and apply its "command" to the player. But the direction > of the movement depends on the orientation of the player. Well, you take > the left joystick data (x and y) and rotate them using the formulas > above, basin on current player orientation. This way, when the left > joystick slides up, the player will always move ahead, along its current > direction. Now I will make an example. > > Suppose your player is at X=0 and Y=0, facing up (0 degrees), and you > move the left joystick "up". You receive y=10 and x=0 from the left > joystick. The above formula gives (cos(0)=1, sin(0)=0): > xr := xp*g92cos - yp*g92sin = 0*1 - 10*0 = 0 > yr := xp*g92sin + yp*g92cos = 0*0 + 10*1 = 10 > > So you add 0 to X and subtract 10 from Y (or add "-yr" to Y). The player > moves up. Note that X is added and Y is subtracted because of the screen. > > Now, suppose that the player instead is facing right (90°). The formula > gives (cos(90)=0, sin(90)=1: > xr := xp*g92cos - yp*g92sin = 0*0 - 10*1 = -10 > yr := xp*g92sin + yp*g92cos = 0*1 + 10*0 = 0 > > So you add -10 to X, and subtract 0 from Y. The player moves left. Why > not to the right? Because if you rotate your head to the left, you turn > 90 degrees, and if you turn your head to the right, you turn -90°. So if > you say that 0° is up and 90° is right, there is something wrong. I hope > that what I write is comprehensible... > > I don't know at which extent your program is already using this strange > coordinates, so I prefer to elaborate no more (a little tired this > night), but by inverting the readings from the joystick, and/or swapping > X and Y from the joystick, or by using "90-angle" instead of "angle" > when calculating cos() and sin(), you should quickly solve without > touching the rest of the program. I presume you should use both > "90-angle" and subtract from Y instead of adding to it, but I am not > sure - sorry. In a few days I will go to visit those URLs you posted, I > am always curious about math and videogames :-)
Doriano, you a genius. =) I adjusted my calculations based on your formulas and I'll be damned it if didn't work perfect on the first try. Amazing... Here's the code in gb: ' Move player relative to player's orientation. worldx = worldx + (Interface.stick_leftx / 131072) * Cos(Rad(orientation)) - (Interface.stick_lefty / 131072) * Sin(Rad(orientation)) worldy = worldy + (Interface.stick_leftx / 131072) * Sin(Rad(orientation)) + (Interface.stick_lefty / 131072) * Cos(Rad(orientation)) For others who may read this in the future, the division by 131072 just compresses the movement range to -0.25 to 0.25 since the gamepad stick input goes from -32767 to 32767, so apply your own number as necessary. Of course as soon as my celebration ended I realized I was now deep in the swamp of getting full-screen rotation working. I've made pretty good progress so far and surprisingly am actually learning a little new math (namely how to rotate point A around point B by angle X). Thanks again Doriano. -- Kevin Fishburne Eight Virtues www:http://sales.eightvirtues.com e-mail:sa...@eightvirtues.com phone: (770) 853-6271 ------------------------------------------------------------------------------ Colocation vs. Managed Hosting A question and answer guide to determining the best fit for your organization - today and in the future. http://p.sf.net/sfu/internap-sfd2d _______________________________________________ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
