[Maya] Get world-space rotatePivot at a specified time

Coding
1

I have some code that gets the rotate pivot of a control in world space:

cmds.xform(ctrlName, q=True, rotatePivot=True, worldSpace=True)

Now would like to get the same information for a different frame/time, without changing the current time. Some people on the internet suggest using getAttr for the .worldMatrix[0] attribute, but the numbers do not match up for me.

The closest I have come is this:

worldMatrix = cmds.getAttr(ctrlName+'.worldMatrix[0]', time=frameNumber)
rotPivot = cmds.getAttr(ctrlName+'.rotatePivot, time=frameNumber)
# 
# Lots of code here to multiply rotPivot by worldMatrix

But that adds a lot of extra code.

Is there some easier way that I am missing?

Edit: Forgot to mention that the “xform” command does not have a “time” parameter, which is why I’m having so much trouble.

2

Can you use pymel? Or the maya api? They both have built in support to matrix multiplication that would turn that into one extra call. Either that or just throw a matrix multiplication method into a math library and call that? I don’t know of a way to get at what you want with just a couple calls aside from doing the math.

3

Originally, I thought the Maya API would be too much set up code. But I tried again after you suggested it. It turns out to be not as many lines as I thought:

wm = cmds.getAttr(nodeName+'.worldMatrix[0]', time=frameNumber)
rotPiv = cmds.getAttr(nodeName+'.rotatePivot', time=frameNumber)[0]
worldMatrix = om.MMatrix()
om.MScriptUtil.createMatrixFromList(wm, worldMatrix)
rotPiv = cmds.getAttr(nodeName+'.rotatePivot')[0]
rotPivVec = om.MPoint(rotPiv[0], rotPiv[1], rotPiv[2], 1.0)
rotPivWorld = rotPivVec * worldMatrix

I also got it working by doing the math manually:

wm = cmds.getAttr(nodeName+'.worldMatrix[0]', time=frameNumber)
rotPiv = cmds.getAttr(nodeName+'.rotatePivot', time=frameNumber)[0]
rotPivWorld = [wm[0]*rotPiv[0] + wm[4]*rotPiv[1] + wm[8]*rotPiv[2] + wm[12],
               wm[1]*rotPiv[0] + wm[5]*rotPiv[1] + wm[9]*rotPiv[2] + wm[13],
               wm[2]*rotPiv[0] + wm[6]*rotPiv[1] + wm[10]*rotPiv[2] + wm[14]]