Hi all,
Given a world matrix, how can I convert this into translate/rotate suitable
for a node with a potentially edited..
- rotateAxis
- rotatePivot
- rotatePivotTranslate
- jointOrient, in the case of joints
In addition to being the child of another node with equally edited pivots
and axes and orientations.
Here’s what works if the target node has a parent, but zeroed out axes,
pivots and orients.
from maya import cmdsfrom maya.api import OpenMaya as om
def setup():
cmds.file(new=True, force=True)
cube1, _ = cmds.polyCube(width=5)
cube2, _ = cmds.polyCube(width=5)
cmds.parent(cube2, cube1)
cmds.rotate(0, 0, 30, cube1)
cmds.rotate(0, 0, -60, cube2)
cmds.move(0, 2, 0, cube1)
cmds.move(5.1, 2, 0, cube2, absolute=True)
# Now make a new world matrix
cube3, _ = cmds.polyCube(width=6, height=0.5, depth=0.5)
cmds.move(4, 2, -2, cube3, absolute=True)
cmds.rotate(25, 15, 50, cube3)
Starting off with some general setup, this is for a scene that looks like
this, where I would like to copy the worldmatrix of one onto the other.
[image: image.png]
Here’s some boilerplate for applying a MMatrix onto any node.
def setMatrix(mobj, matrix):
fn = om.MFnDagNode(mobj)
# Decompose
tm = om.MTransformationMatrix(matrix)
translate = tm.translation(om.MSpace.kPostTransform)
rotate = tm.rotation()
# Assign
tx = fn.findPlug("translateX", False)
ty = fn.findPlug("translateY", False)
tz = fn.findPlug("translateZ", False)
rx = fn.findPlug("rotateX", False)
ry = fn.findPlug("rotateY", False)
rz = fn.findPlug("rotateZ", False)
tx.setDouble(translate.x)
ty.setDouble(translate.y)
tz.setDouble(translate.z)
rx.setMAngle(om.MAngle(rotate.x, om.MAngle.kRadians))
ry.setMAngle(om.MAngle(rotate.y, om.MAngle.kRadians))
rz.setMAngle(om.MAngle(rotate.z, om.MAngle.kRadians))
And finally, the meat of our problem.
def copyMatrix(mobj1, mobj2):
# Parent inverse
obj2fn = om.MFnDagNode(mobj2)
parentInverseMatrixPlug = obj2fn.findPlug("parentInverseMatrix",
True).elementByLogicalIndex(0)
parentInverseMatrix =
om.MFnMatrixData(parentInverseMatrixPlug.asMObject()).matrix()
# Get target worldmatrix we'd like cube2 to receive
obj1fn = om.MFnDagNode(mobj1)
worldMatrixPlug = obj1fn.findPlug("worldMatrix",
False).elementByLogicalIndex(0)
worldMatrix = om.MFnMatrixData(worldMatrixPlug.asMObject()).matrix()
# Cancel out the parent matrix
outMatrix = worldMatrix * parentInverseMatrix
# Apply the thing and profit
setMatrix(mobj2, outMatrix)
setup()
selectionList = om.MSelectionList()
selectionList.add("pCube2")
selectionList.add("pCube3")
cube2obj = selectionList.getDependNode(0)
cube3obj = selectionList.getDependNode(1)
# Copy from pCube3 -> pCube2
copyMatrix(cube3obj, cube2obj)
This works just fine. When you run it, you’ll find pCube2 perfectly aligns
with pCube3, whilst still being parented to pCube1. Great.
[image: image.png]
Problem
Now let’s give pCube2 a custom rotatePivot. We’ll swap out our setup() with
this.
def setup():
cmds.file(new=True, force=True)
cube1, _ = cmds.polyCube(width=5)
cube2, _ = cmds.polyCube(width=5)
cmds.parent(cube2, cube1)
# Here's our rotate pivot
cmds.setAttr(cube2 + ".rotatePivot", -2.5, 0, 0, type="double3")
cmds.move(0, 2, 0, cube1)
cmds.move(5.1, 0, 0, cube2, relative=True)
cmds.rotate(0, 0, 30, cube1)
cmds.rotate(0, 0, -60, cube2)
cube3, _ = cmds.polyCube(width=6, height=0.5, depth=0.5)
cmds.move(4, 2, -2, cube3, absolute=True)
cmds.rotate(25, 15, 50, cube3)
And presto, we’ve got a problem.
[image: image.png]
I figure maybe I could somehow include the pivots..
def copyMatrix(mobj1, mobj2):
# Parent inverse
obj2fn = om.MFnDagNode(mobj2)
parentInverseMatrixPlug = obj2fn.findPlug("parentInverseMatrix",
True).elementByLogicalIndex(0)
parentInverseMatrix =
om.MFnMatrixData(parentInverseMatrixPlug.asMObject()).matrix()
# Get target worldmatrix we'd like cube2 to receive
obj1fn = om.MFnDagNode(mobj1)
worldMatrixPlug = obj1fn.findPlug("worldMatrix",
False).elementByLogicalIndex(0)
worldMatrix = om.MFnMatrixData(worldMatrixPlug.asMObject()).matrix()
rotatePivot = obj1fn.findPlug("rotatePivot",
False).asMDataHandle().asVector()
rotatePivotTranslate = obj1fn.findPlug("rotatePivotTranslate",
False).asMDataHandle().asVector()
# Cancel out the parent matrix
tm = om.MTransformationMatrix(worldMatrix * parentInverseMatrix)
tm.setRotatePivot(om.MPoint(rotatePivot), om.MSpace.kPostTransform, False)
tm.setRotatePivotTranslation(rotatePivotTranslate, om.MSpace.kPostTransform)
# Apply the thing and profit
setMatrix(mobj2, tm.asMatrix())
But it doesn’t work and also makes my brain spin.
So the question is; given an arbitrary world matrix from node A, how can I
apply it to the translate/rotate of node B such that its world matrix is
identical?
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