2D Skeletal Animation System Questions (and Source)

[wagenheimer]

How do you calculate the new X1,Y1 position?

I have the original X0, Y0 values and X1, Y1 Values. And the length of Bone, L.

X1 := X0 + L * Cos(DegToRad(Angle-90));
Y1 := Y0 + L * Sin(DegToRad(Angle-90));

This almost works for me. It only works if the Initial Angle between (X0,Y0) and (X1,Y1) is 0 otherwise I got a small difference after the rotation. And my Math does not help!

Do you have any advice?

[mobilus]

My first advice is to not work with Degrees (Animation.zip):

var 
  S, C: Single;

SinCos(Angle, S, C);
X1:= X0 + L * S;
Y1:= Y0 - L * C;

Your angle must be in the range from 0 to 2*Pi (Figure A, Picture 1):
If Angle > 2*Pi then Angle:= Angle - 2*Pi;
If Angle < 0 then Angle:= Angle + 2*Pi;
(but this should not happen if your animation is prepare properly)

Figure B and C presents the problem that you can have by using Auto Frames.
In my case, one minute of animation takes 40 KB with Auto Frames and 200 KB without Auto Frames - this is still not much, so it is not necessary to implement Auto Frames.