Expression Issue

[inspleak]

Hey guys.. I'm trying to make an object's rotatePivot follow another objects location. And I wanted that to happen all the time so I figured I would make an expression for it.

In my test scene I have a cube who's RP I want to follow the position of a circle in the scene, so I have this expression on the cube:

$circRP = xform -q -ws -rp circ;
setAttr pCube1.rotatePivot $circRP;

It worked the very first time when I pressed "Create" in the expression editor. and now I get an error:

expression -e -s "$circRP = xform -q -ws -rp circ;\r\nsetAttr pCube1.rotatePivot $circRP;\r\n\r" -o "" -ae 1 -uc none moveRP;
// Error: Error reading data element number 1: //
// Error: An execution error occured in the expression moveRP. //

I have a feeling this really isn't the way to do it.. but I can't think of any other way.. any ideas?

Thanks much in advance!

[inspleak]

I stuck this in the expression instead:

$circRP = xform -q -ws -rp circ;
print $circRP;

and it only prints once.. any idea why that might happen as well?

Shouldn't it happen no matter what I do to the scene?

Thanks again!

[failure]

CODE

pCube1.rotatePivot = circ.rotatePivot

[joojaa]

QUOTE(inspleak @ 11/06/05, 02:51 AM)
Shouldn't it happen no matter what I do to the scene?
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NO because its mel your executing and mel does not acrry a trigger on change youll need atlleasta adummy connection or then just timechange will run the expression.

so please note that expressions are NOT equalto MEL

[inspleak]

consider a node route. Make a locator thats constrained to the circle then read that locators localspace wich is in teh target sapece you need!

[inspleak]

QUOTE(failure @ 11/05/05, 08:25 PM)
CODE

pCube1.rotatePivot = circ.rotatePivot

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Also when I try that I get:
// Error: Illegal attribute in expression: circ.rotatePivot //
// Error: Illegal attribute in expression: pCube1.rotatePivot //
// Error: Expression invalid after edit. //

any ideas?

Thanks!

[failure]

CODE
pCube1.rotatePivotX = circ.rotatePivotX;
pCube1.rotatePivotY = circ.rotatePivotY;
pCube1.rotatePivotZ = circ.rotatePivotZ;

Note that this operates in local space of both transform node and it's probably not what you want.

You should just connect the rotatePivot attributes via pointMatrixMult nodes ( to transform source into target's coordinate space )

This is mel, not an expression. It should be run once and it builds node connection:
CODE
polyCube -name "pCube1";
circle -name "cir";
createNode -n pmMult1 pointMatrixMult;
createNode -n pmMult2 pointMatrixMult;
connectAttr cir.rotatePivot pmMult1.inPoint;
connectAttr cir.worldMatrix pmMult1.inMatrix;
connectAttr pmMult1.output pmMult2.inPoint;
connectAttr pCube1.worldInverseMatrix pmMult2.inMatrix;
connectAttr pmMult2.output pCube1.rotatePivot;

I'm just curious why would you want to do such thing? There's absolutely no need for this whatsoever. Not to mention that this kind of thinking generates unwanted loops in dependency graph.

[inspleak]

QUOTE(failure @ 11/06/05, 07:59 AM)
CODE
pCube1.rotatePivotX = circ.rotatePivotX;
pCube1.rotatePivotY = circ.rotatePivotY;
pCube1.rotatePivotZ = circ.rotatePivotZ;

Note that this operates in local space of both transform node and it's probably not what you want.

You should just connect the rotatePivot attributes via pointMatrixMult nodes ( to transform source into target's coordinate space )
This is mel, not an expression. It should be run once and it builds node connection:
CODE
polyCube -name "pCube1";
circle -name "cir";
createNode -n pmMult1 pointMatrixMult;
createNode -n pmMult2 pointMatrixMult;
connectAttr cir.rotatePivot pmMult1.inPoint;
connectAttr cir.worldMatrix pmMult1.inMatrix;
connectAttr pmMult1.output pmMult2.inPoint;
connectAttr pCube1.worldInverseMatrix pmMult2.inMatrix;
connectAttr pmMult2.output pCube1.rotatePivot;

I'm just curious why would you want to do such thing? There's absolutely no need for  this whatsoever. Not to mention that this kind of thinking generates unwanted loops in dependency graph.
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Thanks again for the help... I realize that it could create loops that could be bad, but if you are careful on how it is set up, it will work just fine. The reason that I want to try something like this is so that I can control the point for which an object rotates, based the location of another object...

so for instance if I am setting up a foot rig, and I want to rotate about the ankel, then I want the rotation point for the toe (or the tip of the foot) to move with it. Then I can rotate about the toe as well even after I have rotated the ankle... Its a tough one to explain, hopefully you see what I'm trying to do..

The one thing that I was hoping for in Maya 7 was a sort of "Action Center" like Modo supposedly has. That way you could make multiple pivot points to rotate around and still have all of the controls go with it.

Thanks again!