2D Skeletal Animation System Questions (and Source)

[Carver413]

maybe this will help
http://content.gpwiki.org/index.php/...c_Bones_System

[mobilus]

This is my solution.

A few words of introduction: We operate only on angles (one bone = one angle) and one start point (X0, Y0) from figure B (picture 1) - this is the only data that we need to read and write to the file (for one frame of animation).
Additionally, you can have a bone length L, but this is unnecessary when you have a human bones (ideal human proportion) or you can get L from sprite length.

Algorithm:
- starting from the point (X0, Y0), Figure B (picture 1).
- we have angle (a), length of bone (L1), start point (X0,Y0), so we can calculate the point (X1, Y1). (X1, Y1) is a central position of our next sprite (be sure your sprite can be rotated from a center (picture 2, figure A))
- if we have (X1, Y1), (b) and (L2), we can calculate (X2, Y2) and next (X3, Y3)
- we do this same for left and right leg (figure C), and left and right hand (figure D)

Optimization:
This method requires a large number of calculations, but it does not need a lot of resources to read and write. To better work with animation, we can use KeyFrames - write data only for KeyFrames, and the rest is calculated automatically (picture 2, Figure B). It's not difficult to calculate AutoFrames if we operate on angles.


Result (AutoFrames = 5):
http://www.youtube.com/watch?v=igSRP0J5q_I

[wagenheimer]

Thanks Mobilus!

Your info will be very useful! =)

I think I have understood! I will try to make something here!

Thanks

[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.