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clamp object to orbit around it’s on axis
Hi Everyone,
I am trying to create an onscreen (in comp window) GUI. Basically what I am trying to do is create a rotation slider. I have a square box icon that i want to rotate around an offset axis when you drag the object in the x direction. I thought I had a solution but the object spins in either an increasing or decreasing spiral even though I have clamped the position values. I have attached a still image to show the setup, with the parenting and clamping expressions etc. I can attach a afx project if it helps.Thanks in advance,
Brad -
8 Replies
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> I have attached a still image..
The image seems to be missing.
Dan
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Sorry Dan, haven’t uploaded images before, hope this works,
Cheers
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I think you’re going to have better luck with something like this:
r = 239;
center = thisComp.layer("Object A").transform.position;
try{
center + r*normalize(value-center);
}catch (err){
value
}Dan
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Hi Dan, thanks for your reply. I have tried your idea. I applied the code to the “Object A” position, but I am still having the same issue of when I drag object along it moves in a decreasing or ascending spiral and doesn’t keep a constant distance radius from the offset Null. I don’t think that I mentioned that “object A” is parented to the Null, would this be causing the issue?
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I guess I’m still confused about what you’re trying to do. The expression was for the orbiting object, not “Object A”.
Dan
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Hi Dan, I have attached a project file that should explain better what I am trying to achieve. Basically The red null is the controller for a characters hand. The Object A is the rotation of the characters hand. I am trying to create animation controls that are all located in the comp window. So when you drag object A in the up and down “Y” position you will see that the layer as it rotates around moves out of orbit and ends up about 100 pixels or more to the bottom of where it started. Basically I want the layer to follow around the red nul in a perfect circle and when it comes back on itself at 360 degrees it will be in the same position as it started. Do you think it will be possible?
Cheers
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OK – try this. Unparent Object A from the null. Turn off all expressions for the null and the object, and position Object A to the right of the null. Use this for Object A’s position:
r = 239;
center = thisComp.layer("Orbvit Centre Null").transform.position;
try{
center + r*normalize(value-center);
}catch (err){
value
}
and this for its rotation:
r = 239;center = thisComp.layer("Orbvit Centre Null").transform.position;
try{
v = transform.position-center;
radiansToDegrees(Math.atan2(v[1],v[0]));
}catch (err){
0
}Then link the null's rotation to that of Object A.
Something like that.
Dan
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Awesome, works well! Thanks again Dan for all your help!
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