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A (kinda) IK question…
I was using the tan2() expression to get an “arm” to point at a target…it looked simply like this (from http://www.jjgifford.com):
this_point=position;
that_point=this_comp.layer(“target”).position;
delta=sub(this_point, that_point);
angle=Math.atan2(delta[1], delta[0]);
radians_to_degrees(angle);It worked great, the anchor point of the ‘arm’ was the shoulder. Okay, so Part 2 was to simply attach this arm to a body? Right? Wrong. The second it was parented to the body, everything went fairly ‘whack’. Is there anything I can do about this? Would this require the more complex IK solution from Ebberts/Motionscript? I don’t think so – because I don’t want the rotation of the arm (or position of the target) to effect the rotation of the ‘body’.
-echo
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3 Replies
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Changing your first line to this should do the trick:
this_point=toWorld(anchor_point);
Dan
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Ah, thank you very much. And indeed it does work for the position, but – and stop me if it’s just not possible – but because it is the “body”, is there anways to affect the ‘arm’ rotation – while the arm still points at the target?
As it stands right now, if I rotate the body, the arm rotates along with it, but no longer points at the target. I was thinking about turning on the 3d toggle and using the orientation as a quick fix…perhaps I shall try that right now…but your thoughts on he matter would be much appreciated.
-eho
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I think you just need to subtract the rotation of the body from your result, like this:
radians_to_degrees(angle) – thisComp.layer(“body”).rotation;
Dan
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