The value depends on the movement of the object into X direction. Every pixel the object moves into X direction increases the value a little bit. Once end has been reached the value is reset to begin. In contrast to
Anim_X the value moves towards end not depending on whether the object moves to the left or to the right.
See the
animation documentation for further explanations of the animation system.
PlayAnimation("Walk", 5, Anim_AbsX(0, 0, GetAnimationLength("Walk"), 20), Anim_Const(1000));
Plays the animation "Walk" in slot 5, superimposing any other potential animations in slot 5. The animation is played the faster the faster the object moves into X direction. Once it moved 20 pixels the animation has been played from begin to end and restarts at its beginning.