# jointChain.py
import sys
import maya.OpenMaya as OpenMaya
import maya.OpenMayaMPx as OpenMayaMPx
import maya.OpenMayaAnim as OpenMayaAnim
kPluginCmdName = 'myJointChain'
# The length of the chain.
kLengthFlag = '-l'
kLengthLongFlag = '-length'
defaultLength = 3
jointDistance = 5 # the distance between two joints
jointOrientation = 20 # degrees.
##########################################################
# Plug-in
##########################################################
class JointChainCommand(OpenMayaMPx.MPxCommand):
def __init__(self):
''' Constructor. '''
OpenMayaMPx.MPxCommand.__init__(self)
def parseArgs(self, pArguments):
''' Parses the command's arguments. '''#解析命令的引數
# Set the default chain length in case there are no arguments.如果沒有設定引數則設定為預設值
global defaultLength
self.length = defaultLength
# Obtain the flag value, if the flag is set.如果標示被設定則獲得標示的數值
argData = OpenMaya.MArgParser( self.syntax(), pArguments )
if argData.isFlagSet( kLengthFlag ):
# Get the value associated with the flag as an integer.得到的值與標示作為一個整型的關聯
flagValue = argData.flagArgumentInt( kLengthFlag, 0 )
# Make sure this value is larger than the default length.確保該數值大於預設數值
if flagValue > defaultLength:
self.length = flagValue
def doIt(self, pArguments):
''' Command Execution. '''#執行命令
# Parse the passed arguments.解析傳遞引數。
self.parseArgs( pArguments )
# Create an instance of an MDagModifier to keep track of the created objects,建立一個MDagModifier的例項來對建立的物體進行跟蹤
# and to undo their creation in our undoIt() function.至於撤銷操作是在undoIt()的功能下
self.dagModifier = OpenMaya.MDagModifier()
# Create the joint MObjects we will be manipulating.我們建立將要操作joint MObjects
self.jointObjects = []
for i in range(0, self.length):
if i == 0:
# The first joint has no parent.第一個骨節沒有上層骨節
newJointObj = self.dagModifier.createNode( 'joint' )
else:
# Assign the new joint as a child to the previous joint.分配新的骨節作為子骨子給之前的骨節
newJointObj = self.dagModifier.createNode( 'joint', self.jointObjects[i-1] )
# Keep track of all the joints created.繼續建立所有的骨節
self.jointObjects.append( newJointObj )
# Create the inverse kinematic effector MObject. The effector is a child of the last joint object.建立IKMobject，IK是最後骨節的子物體
# The [-1] index is a Python-specific way of referring to the last item in a list.
self.effectorObj = self.dagModifier.createNode( 'ikEffector', self.jointObjects[-1] )
# Invoke the command's redoIt() function to actually create and manipulate these objects.呼叫命令的redoIt（）函式建立和操縱這些物件。
self.redoIt()
def redoIt(self):
''' Create and manipulate the nodes to form the joint chain. '''#建立和形成骨節鏈
# Perform the operations enqueued within our reference to MDagModifier.在MDagModifier內執行排列操作
self.dagModifier.doIt()
#=======================================
# JOINT MANIPULATION#骨節控制
#=======================================
# We can now use the function sets on the newly created DAG objects.現在我們可以使用新建立的DAG物件的功能集
jointFn = OpenMayaAnim.MFnIkJoint()
for i in range( 1, len( self.jointObjects ) ):
jointFn.setObject( self.jointObjects[i] )
# We set the orientation for our joint to be 'jointOrientation' degrees, to form an arc. 我們為骨節設定方向（定義的變數jointOrientation這麼多）度，形成弧形
# We use MFnIkJoint.setOrientation() instead of MFnTransform.setRotation() to let the
# inverse-kinematic handle maintain the curvature.我們使用MFnIkJoint.setOrientation()來取代MFnTransform.setRotation()來讓IK手柄保持曲率
global jointOrientation
rotationAngle = OpenMaya.MAngle( jointOrientation, OpenMaya.MAngle.kDegrees )
jointFn.setOrientation( OpenMaya.MEulerRotation( rotationAngle.asRadians(), 0 , 0, OpenMaya.MEulerRotation.kXYZ ) )
# We translate the joint by 'jointDistance' units along its parent's y axis.我們沿著父骨節的Y軸移動jointDistance（這麼多）數值
global jointDistance
translationVector = OpenMaya.MVector( 0, jointDistance, 0 )
jointFn.setTranslation( translationVector, OpenMaya.MSpace.kTransform )
#=======================================
# IK HANDLE MANIPULATION#IK手柄的控制
#=======================================
# We will use the MEL command 'ikHandle' to create the handle which will move our joint chain. This command
# will be enqueued in our reference to the MDagModifier so that it can be undone in our call to MDagModifier.undoIt().
#我要使用mel中的 'ikHandle' 命令來建立可以控制骨節鏈的手柄，該命令將被排入我們參考MDagModifier，以便它可以在我們的呼叫後對MDagModifier.undoIt（）被撤消。
# Obtain the DAG path of the first joint.設定第一個骨節的DAG路徑
startJointDagPath = OpenMaya.MDagPath()
jointFn.setObject( self.jointObjects[0] )
jointFn.getPath( startJointDagPath )
# Obtain the DAG path of the effector.設定操縱器的DAG路徑
effectorDagPath = OpenMaya.MDagPath()
effectorFn = OpenMayaAnim.MFnIkEffector( self.effectorObj )
effectorFn.getPath( effectorDagPath )
# Enqueue the following MEL command with the DAG paths of the start joint and the end effector.
self.dagModifier.commandToExecute( 'ikHandle -sj ' + startJointDagPath.fullPathName() + ' -ee ' + effectorDagPath.fullPathName() )
# We call MDagModifier.doIt() to effectively execute the MEL command and create the ikHandle. 我們呼叫MDagModifier.doIt（）有效地執行MEL命令建立ikHandle
self.dagModifier.doIt()#《《《《《《《《《《《《《《《《《《《《《事實上是 OpenMaya.MDagModifier.doIt()
def undoIt(self):
''' Undo the command. '''
# This call to MDagModifier.undoIt() undoes all the operations within the MDagModifier.這個呼叫MDagModifier.undoIt（）撤消所有在MDagModifier內的操作
# Observe that the number of calls to MDagModifier.undoIt() does not need to match the number of calls to MDagModifier.doIt().
#觀察呼叫MDagModifier.undoIt()的數目不需要匹配MDagModifier.doIt()的呼叫數目
self.dagModifier.undoIt()#《《《《《《《《《《《《《《《《《《《《《事實上是 OpenMaya.MDagModifier.undoIt()
def isUndoable(self):
''' This function must return True to indicate that it is undoable. ''' #這個函式必須返回true以指示它是不可撤銷的
return True
##########################################################
# Plug-in initialization.#外掛的安裝
##########################################################
def cmdCreator():
''' Creates an instance of the command. '''#註冊這個命令
return OpenMayaMPx.asMPxPtr( JointChainCommand() )
def syntaxCreator():
''' Defines the argument and flag syntax for this command. '''#註冊這個命令的引數以及標示
syntax = OpenMaya.MSyntax()
syntax.addFlag( kLengthFlag, kLengthLongFlag, OpenMaya.MSyntax.kDouble )
return syntax
def initializePlugin( mobject ):
''' Initializes the plug-in. '''#安裝外掛
mplugin = OpenMayaMPx.MFnPlugin( mobject )
try:
mplugin.registerCommand( kPluginCmdName, cmdCreator, syntaxCreator )
except:
sys.stderr.write( 'Failed to register command: ' + kPluginCmdName )
raise
def uninitializePlugin( mobject ):
''' Uninitializes the plug-in. '''#解除安裝外掛
mplugin = OpenMayaMPx.MFnPlugin( mobject )
try:
mplugin.deregisterCommand( kPluginCmdName )
except:
sys.stderr.write( 'Failed to unregister command: ' + kPluginCmdName )
raise
##########################################################
# Sample usage.
##########################################################
'''
# Copy the following lines and run them in Maya's Python Script Editor:
import maya.cmds as cmds
cmds.loadPlugin( 'jointChain.py' )
cmds.myJointChain( length=4 )
'''