Disclaimer:
All code here is provided as is without support.
Use at your own risk! These posts assume you have some knowledge of import/running python script in maya. If Gifs/Images are not displaying in Chrome try a different browser.
So now we have a handle of getting a selection, or building an MSelectionList()to get MObjects to manipulate in scene.
Now another big part of our day is creating nodes / adding or removingattributes / querying attributes values / connecting or disconnecting attributes.
Below might look familiar those of you using cmds a lot;
from maya import cmdscurSel = cmds.ls(sl=True)srcNode = curSel[0]destNode = curSel[1]# connectcmds.connect("{}.translate".format(srcNode), "{}.translate".format(destNode), force=True)# getAttrtransX = cmds.getAttr("{}.translate".format(srcNode))# setAttrcmds.setAttr("{}.translateX".format(srcNode), 10)# createNodenewNode = cmds.createNode("transform", name="Fart")Yes it is true that we’re about to convert this into more lines using om2.And yes I still do a lot of prototyping in cmds when mashing stuff togetherin the script editor, but for reuse tools, I will most likely convert those scripts to om2,even the ones that might not see a lot of benefit speed wise, as it’s justgood practise and I find it fun to do shrug.
from maya.api import OpenMaya as om2from maya import cmds# mDagMod for creating / handling DGNodesmdgmod = om2.MDGModifier()# mDagMod for creating / handling DagNodesmDagMod = om2.MDagModifier()curSel = om2.MGlobal.getActiveSelectionList()srcNode = curSel.getDependNode(0)destNode = curSel.getDependNode(1)# connect# Find first source plug, find dest plug, use the modifier to connect themmFn = om2.MFnDependencyNode(srcNode)srcPlug = mFn.findPlug("translate", False)mFn.setObject(destNode)destPlug = mFn.findPlug("translate", False)if destPlug.isConnected: # Find what it is connected to and disconnect it first! # Since this is a destination only one thing can be connected to it. # Else if we're looking for all connected to a source we can use connectedTo() src = destPlug.source() mDagMod.disconnect(srcPlug, destPlug)mDagMod.connect(srcPlug, destPlug)mDagMod.doIt()# getAttr# some plugs are compounds, some are arrays, some are floats / bool / shorts / double etcsrcTrans = [srcPlug.child(x).asFloat() for x in range(srcPlug.numChildren())]print(srcTrans)# setAttrsrcPlug.child(0).setFloat(10)# createNode# Depending on if you are making a DAGNode or DGNode you'll need to use either a# MDagModifier or a MDGModifier() eg: you can't make a joint with a MDGModifier()nodeName = "Fart"# We can use cmds here to check for the node as the queries in cmds are pretty# fast.if not cmds.objExists(nodeName): newNode = mDagMod.createNode("transform") mDagMod.renameNode(newNode, nodeName) mDagMod.doIt()# Note you might want to use the MFnDependencyNode.create() method, but this will# create the node in scene as soon as you call this. Using the MDG or MDag modifiers# lets you queue up xNum of operations and using the doIt() to perform them in one# go. Which can be a HUGE time saver when building complex scenes.So what about this:
”# some plugs are compounds, some are arrays, some are floats / bool / shorts / double etc”
If you’re confused what kind you’re dealing with you can use Maya’s nodeEditorto try to figure it out.
An MPlug has a couple methods to help out.
MPlug.isArray()MPlug.isCompound()MPlug.isElement()MPlug.isChild()The main difference between an Array and a Compound being;
- Arrays uses physical / logical indices
- Compounds have child(x)
Lets look at this in code:
from maya.api import OpenMaya as om2# mDagMod for creating / handling DAGNodesmDagMod = om2.MDagModifier()mDGMod = om2.MDGModifier()curSel = om2.MGlobal.getActiveSelectionList()srcNode = curSel.getDependNode(0)destNode = curSel.getDependNode(1)# Connect the CHILDREN of attributes "translate", "rotate", "scale" to# another transform's "translate", "rotate", "scale"mFn = om2.MFnDependencyNode()for x in range(3): mFn.setObject(srcNode) for plugName in ("translate", "rotate", "scale"): mFn.setObject(srcNode) srcPlug = mFn.findPlug(plugName, False) srcMPlug = srcPlug.child(x) mFn.setObject(destNode) destPlug = mFn.findPlug(plugName, False) destMPlug = destPlug.child(x) mDagMod.connect(srcMPlug, destMPlug)# Note how we've stacked all these connections BEFORE calling the doIt()mDagMod.doIt()# Now the worldMatrix (which is an Array)mFn.setObject(srcNode)srcPlug = mFn.findPlug("worldMatrix", False)srcWorldMatrix0 = srcPlug.elementByLogicalIndex(0)mFn.setObject(destNode)decomposeMatrix = mDGMod.createNode("decomposeMatrix")# This node NEEDS TO EXIST to connect to! So we have to create it now!mDGMod.doIt()mFn.setObject(decomposeMatrix)destPlug = mFn.findPlug("inputMatrix", False)mDagMod.connect(srcWorldMatrix0, destPlug)mDagMod.doIt()Finally it’s probably important to know the difference between a logical indexand a physical one… from the docs… yes the info is all there :P
Logical Index:
“This method will find and return a plug with the given logical index.
The logical index is the sparse array index used in MEL scripts.If a plug does not exist at the given Index, Maya will create a plug at that index.This is not the case with elementByPhysicalIndex(). If needed, elementByLogicalIndexcan be used to expand an array plug on a node.
It is important to note that Maya assumes that all such plugs serve a purpose and it will not free non-networkedplugs that result from such an array expansion.”
Physical Index:
“This method will find and return a plug with the given physical index.
The index can range from 0 to numElements() - 1. This function is particularlyuseful for iteration through the element plugs of an array plug. It isequivalent to operator [] (int) This method is only valid for array plugs.
If the returned plug is networked, the networked plug will be returned.Otherwise, a non-networked plug will be returned.”
.. onwards… MObject
