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Pilot Season – Day 13 – Scripting Version of fk ik Switch

Published by Raffaele on 8 July, 2017

Day 13 of the stream, we keep keeping on with scripting until we obtain the right numbers and get ourselves ready to implement the dynamic, callback driven version

We conclude the scripting tangent required to deploy an actual dynamic FK to IK switch.

With OpenMaya2 introduced in the Day 12 stream, the design of the callback done and some attributes at hand, we finally get onto writing the actual code necessary for the callback to retrieve and transform the value until we obtain the right numbers.

As in previous scripting posts and videos the transcription of the code to the point we left it at the end of the episode is available at the end of this post.

Next stream all we’ll have to will be converting it to an actual callback and possibly ensuring it’s re-installed at scene open, but for now enjoy the scripting part taken from snippets to useful numbers:

 

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from maya.api import _OpenMaya_py2 as om2
from maya import cmds
import math
 
def iterSelection():
    """
    generator style iterator over current Maya active selection
    :return: [MObject) an MObject for each item in the selection
    """
    sel = om2.MGlobal.getActiveSelectionList()
    for i in xrange(sel.length()):
        yield sel.getDependNode(i)
 
 
_MAYA_MATRIX_ATTRIBUTE_NAME = 'worldMatrix'
def wMtxFromMob(node_mob):
    """
    finds the world matrix attribute and returns its value in matrix form
    :param node_mob: [MObject] the node to get the world matrix from 
    :return: [MMatrix] the matrix value of the world transform on the argument node
    """
    if not node_mob.hasFn(om2.MFn.kDagNode):
        return None
 
    mfn_dag = om2.MFnDagNode(node_mob)
    wMtxPlug = mfn_dag.findPlug(_MAYA_MATRIX_ATTRIBUTE_NAME, False)
    elPlug = wMtxPlug.elementByLogicalIndex(0)
 
    node_mob_attr = elPlug.asMObject()
    mfn_mtxData = om2.MFnMatrixData(node_mob_attr)
    return mfn_mtxData.matrix()
 
 
def mtxFromPlugSource(plug):
    """
    takes a plug and retrieves the plug's source plug
      then will try to initialise matrix data from it and return it
      if valid
    :param plug: [MPlug] a plug connected to a matrix type source
    :return: [MMatrix | None]
    """
    if plug.isDestination:
        mtxPlug = plug.source()
        node_mob_attr = mtxPlug.asMObject()
        if node_mob_attr.hasFn(om2.MFn.kMatrixAttribute):
            mfn_mtxData = om2.MFnMatrixData(node_mob_attr)
            return mfn_mtxData.matrix()
    return None
 
 
def mPointFromPlugSource(plug):
    """
    similar to mtxFromPlugSource but will retrieve a translate compound source
    :param plug: [MPlug] a plug connected to a translate compound triplet source
    :return: [MPoing | None]
    """
    if plug.isDestination:
        sourcePlug = plug.source()
        if not  sourcePlug.isCompound or not sourcePlug.numChildren() == 3:
            return None
 
        mp = om2.MPoint()
        returnPoint = [False,False,False]
        for i in xrange(sourcePlug.numChildren()):
            realName = sourcePlug.child(i).partialName(includeNodeName = False, useAlias = False)
            if realName == 'tx':
                mp.x = sourcePlug.child(i).asFloat()
                returnPoint[0] = True
            elif realName == 'ty':
                mp.y = sourcePlug.child(i).asFloat()
                returnPoint[1] = True
            elif realName == 'tz':
                mp.z = sourcePlug.child(i).asFloat()
                returnPoint[2] = True
        if all(returnPoint):
            return mp
        return None
 
 
_MAYA_OUTPUT_ATTRIBUTE_NAME = 'output'
def getMRotFromNodeOutput(node_mob, rotOrder = om2.MEulerRotation.kXYZ):
    """
    finds the angular output of the argument node and returns it
     as a Euler rotation where that angle is the X element
    :param node_mob: [MObject] the node to get the output port from
    :param rotOrder: [int] the factory constant for the desired rotation order
                            the returned Euler rotation should be set to
    :return: [MEulerRotation] the Euler rotation composition where the
                                angular output on the argument node is the X value
    """
    mfn_dep = om2.MFnDependencyNode(node_mob)
    angle = om2.MAngle(0.0)
    if node_mob.hasFn(om2.MFn.kAnimBlend) and mfn_dep.hasAttribute(_MAYA_OUTPUT_ATTRIBUTE_NAME):
        plug = mfn_dep.findPlug(_MAYA_OUTPUT_ATTRIBUTE_NAME, False)
        angle = plug.asMAngle()
 
    rot = om2.MEulerRotation(angle.asRadians(), 0.0, 0.0, rotOrder)
    return rot
 
 
# A dictionary of all attributes we're interested in by name, ready
#   to accept values for each.
attribs = {
           'blendedRotation': None,
           'fk_bfr_mtx': None,
           'ik_bfr_mtx': None,
           'ikPedalOffset': None,
           }
 
 
mobTuple = tuple(iterSelection())
if mobTuple:
    mfn_dep = om2.MFnDependencyNode(mobTuple[0])
    plug = om2.MPlug()
    if mfn_dep.hasAttribute("FKIK_switch"):
        plug = mfn_dep.findPlug("FKIK_switch", False)
 
    if plug.isNull:
        print("invalid selection, no FKIK_switch attribute found on first selected item")
    else:
        for eachPName in attribs.iterkeys():
            plug = mfn_dep.findPlug(eachPName, False)
            attribs[eachPName] = plug
 
    isValid = True
    for p in attribs.itervalues():
        if p is None:
            isValid = False
            break
 
    if isValid:
        blendedRot = fk_bfr_mtx = ik_bfr_mtx = ikPedalOffset = None
        blendedRot = attribs.get("blendedRotation").source().asMAngle().asRadians()
        fk_bfr_mtx = mtxFromPlugSource(attribs.get("fk_bfr_mtx"))
        ik_bfr_mtx = mtxFromPlugSource(attribs.get("ik_bfr_mtx"))
        ikPedalOffset = mPointFromPlugSource(attribs.get("ikPedalOffset"))
 
        projectedLen = ikPedalOffset.y
        z = math.sin(blendedRot) * projectedLen
        y = (1.0-math.cos(blendedRot)) * -projectedLen
else:
    print("invalid selection count, nothing found selected from iterator")
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