View Full Version : orbiting expression

01 January 2008, 04:25 PM
Hey guys, I am just starting to get into Expressions, well object based expressions anyway, I have a bit of experience with particle expressions.

Anyways, I was wondering how I would make an object orbit another object, and how I would get it to maintain a constant distance if the object being orbited was moving.

Any ideas would be much appreciated!!


01 January 2008, 05:03 PM
well you can just put the pivot of the orbiting object to the object in the center and do some rotations.

if you'd like to put in some maths you can use sine and cosine functions or matrix multiplications, whatever :D

but i think the easiest way would be to use the pivot

01 January 2008, 06:09 PM
This does it...

polySphere -r 1;
polySphere -r 0.25;
expression -s "float $orbitRad1 = 5.0;\r\nfloat $orbitRad2 = 2.0;\r\npSphere1.translateX = $orbitRad1 * sin(deg_to_rad(4*frame));\r\npSphere1.translateZ = $orbitRad1 * cos(deg_to_rad(4*frame));\r\npSphere2.translateX = pSphere1.translateX + $orbitRad2 * sin(deg_to_rad(16*frame));\r\npSphere2.translateZ = pSphere1.translateZ + $orbitRad2 * cos(deg_to_rad(16*frame));" -o pSphere1 -ae 1 -uc all;

playbackOptions -min 0 -max 360 ;

but expressions are the slowest way....I agree with the pivot idea.

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01 January 2008, 06:09 PM
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