使用 Python 在 Maya 中旋转父级后计算父级控制器的新位置

Question

我正在创建代码以根据它在 Maya 中的关键帧位置创建控制器的运动路径。尝试使用此代码创建父控制器的运动路径时遇到问题。如果我旋转并平移父对象，则生成的运动路径不会反映实际的运动路径。相反，它会创建运动路径，就好像它不受父级影响一样。我环顾四周，找到了使用矩阵变换将旋转应用于当前位置的信息，但它似乎旋转得太多了。我已经包含了创建运动路径的函数，它有点长，但是在处理上躯干控制器时，不工作的部分在 else 语句中。

旧代码

#
# This function creates an animation curve within the scene that follows the path of motion
# of the selected controller. It requires keyframe information in order to genereate the curve
# and uses the range of frames given by the user.
#
def createAnimCurve( bodyField, startField, endField, firstColor ):
    # Takes the value of the text field to select the controller
    obj = cmds.textField(bodyField, query=True, text=True)
    print obj
    # Takes in the string input of the paramter values and turns them into integer values
    startFrame = cmds.intField(startField, query=True, value=True)
    print startFrame
    endFrame = cmds.intField(endField, query=True, value=True)
    print endFrame
    color = cmds.colorIndexSliderGrp( firstColor, query=True, value=True ) - 1
    print color

    if obj == "":
        cmds.warning( "WARNING: Need to Select Body Part from Diagram" )
        return
    if cmds.objExists(obj[:-3]+'Path'):
        # Creates a warning pop up that double checks if the user wants to remove the curve
        delRes = cmds.confirmDialog( title='Delete Path Warning', message='Recreation will delete current path. Are you sure?', button=['Yes','No'], defaultButton='Yes', cancelButton='No', dismissString='No' )
        # If yes then the curve is deleted
        if delRes == 'Yes':
            #cmds.delete(obj[:-3]+'ScalePath')  
            #cmds.delete(obj[:-3]+'ScalePath_LOC')  
            cmds.delete(obj[:-3]+'Path')     
            cmds.delete(obj[:-3]+'Path_LOC')
        else:
            return
    # Sorts through the list of keyframes of the selected obj from the selected time line
    global keyframes
    keyframes = sorted(list(set(cmds.keyframe(obj, q=True, time=(startFrame,endFrame), timeChange=True))))
    # Creates the arrays for the required point positions
    points = []
    centerPoints = []
    centerRotates = []
    combinedPoints = []

    # Special cases for controllers that are named differently than their joints
    if obj == "L_foot_CTL" or obj == "R_foot_CTL":
        loc = obj[:-4] + "Ankle_LOC"
    elif obj == "M_upTorso_CTL":
        loc = "M_spineTip_LOC"
    else:    
        loc = obj[:-3] + "LOC"
    # Grabs the original world space position to calculate the approraite motion points
    locPos = cmds.getAttr(loc+".translate")
    centerLocPos = cmds.getAttr("M_centerMass_LOC.translate")

    #for step in range( startFrame, endFrame+2, int(curveCVstep)):
    for step in range(len(keyframes)):
        # Moves throughout the specified timeline to find point results
        cmds.currentTime( keyframes[step] )
        if obj != "M_upTorso_CTL":
            # Queries the position of the controller to draw the curve
            # Adds the position of the controller in world space to draw it relative to the control
            pos = cmds.xform( obj,q=True,ws=True,t=True )
            pos[0] = pos[0] + locPos[0][0]
            pos[1] = pos[1] + locPos[0][1] 
            pos[2] = pos[2] + locPos[0][2]
            # convert the tuple (vector) to a string
            points.append(pos)
            print pos
        else:
            spineLength = cmds.getAttr('spineCurveInfo.arcLength')

            # Queries the position of the controller to draw the curve
            # Adds the position of the controller in world space to draw it relative to the control
            # adds in the spine length to the y position to take into consideration the offset of the centerMass controller
            pos = cmds.xform( obj,q=True,ws=True,t=True )
            pos[0] = pos[0] + locPos[0][0]
            pos[1] = pos[1] + locPos[0][1]
            pos[2] = pos[2] + locPos[0][2]
            # convert the tuple (vector) to a string
            print "Printing out points"
            points.append(pos)
            print pos

            # Queries the position of the center of mass controller 
            centerPos = cmds.xform( "M_centerMass_CTL",q=1,os=1,t=1 )
            centerPos[0] = centerPos[0] #+ centerLocPos[0][0]
            centerPos[1] = centerPos[1] #+ centerLocPos[0][1]
            centerPos[2] = centerPos[2] #+ centerLocPos[0][2]
            # convert the tuple (vector) to a string
            print "Printing out center Points"
            centerPoints.append(centerPos)
            print centerPos

            # Combine the two point positions to find the relative position 
            combinedPos = []
            combinedPos1 = pos[0] + centerPos[0]
            combinedPos.append(combinedPos1)
            combinedPos2 = pos[1] + centerPos[1]
            combinedPos.append(combinedPos2)
            combinedPos3 = pos[2] + centerPos[2]
            combinedPos.append(combinedPos3)
            print "Printing out combined Points"
            print combinedPos

            # Queries the rotation of the center of mass controller
            #centerRot = cmds.xform( "M_centerMass_CTL",q=1,ws=1,ro=1 )
            #centerRotates.append(centerRot)
            #print "Printing out rotations"
            #print centerRot
            # applies rotation of the center of mass controller to the upper torso controller
            # rotation around the Z axis
            #tempX = combinedPos[0]*math.cos(math.radians(centerRot[2])) - combinedPos[1]*math.sin(math.radians(centerRot[2]))
            #tempY = combinedPos[0]*math.sin(math.radians(centerRot[2])) + combinedPos[1]*math.cos(math.radians(centerRot[2]))
            # rotation around the Y axis
            #tempX2 = tempX*math.cos(math.radians(centerRot[1])) + combinedPos[2]*math.sin(math.radians(centerRot[1]))
            #tempZ = combinedPos[2]*math.cos(math.radians(centerRot[1])) - tempX*math.sin(math.radians(centerRot[1]))
            # rotation around the X axis
            #tempY2 = tempY*math.cos(math.radians(centerRot[0])) - tempZ*math.sin(math.radians(centerRot[0]))
            #tempZ2 = tempY*math.sin(math.radians(centerRot[0])) + tempZ*math.cos(math.radians(centerRot[0]))

            #combinedPos[0] = tempX2
            #combinedPos[1] = tempY2
            #combinedPos[2] = tempZ2
            #print "Printing out rotated Points"
            combinedPoints.append(combinedPos)
            print combinedPos

    # if the obj is the upper torso controller we need to take into consideration the center of mass controller
    # Creates the motion curve with the required cvs
    if obj == "M_upTorso_CTL":
        cur = cmds.curve(d=2, ws=True, p=combinedPoints, n=obj[:-3]+'Path')
        cmds.setAttr(cur + '.overrideEnabled', 1)
        cmds.setAttr(cur + '.overrideColor', color)
        print cur
        cmds.move(points[0][0], points[0][1], points[0][2], cur+".scalePivot", cur+".rotatePivot", absolute=True)
    else:
        cur = cmds.curve(d=2, ws=True, p=points, n=obj[:-3]+'Path')
        cmds.setAttr(cur + '.overrideEnabled', 1)
        cmds.setAttr(cur + '.overrideColor', color) 
        print cur
        cmds.move(points[0][0], points[0][1], points[0][2], cur+".scalePivot", cur+".rotatePivot", absolute=True)
    # command that runs through each cv of the curve and returns their position within a list.
    cvs = cmds.getAttr( obj[:-3]+'Path.cv[*]' )
    print cvs

    global initCVS
    initCVS = cvs
    # Create a locator for the motion path that the controller will now follow
    locate = cmds.spaceLocator( n=obj[:-3]+"Path_LOC" )
    #for step in range( startFrame, endFrame+2, int(curveCVstep)):
    for step in range(len(keyframes)):
        # Moves throughout the specified timeline to find point results
        cmds.currentTime( keyframes[step] )
        # Moves the locator to match the position of the controller
        cmds.move( cvs[step][0], cvs[step][1], cvs[step][2], locate)
        # Keyframes the locator
        cmds.setKeyframe( locate )
    # Position obj at the location of locate.
    cmds.pointConstraint( locate, obj, n=obj[:-3]+"LOC1_PNT" )
    cmds.setAttr( loc+'.visibility', 0)
    # keys the weight of the point constraint to 0 before and after time frame (set to 1 during time frame)
    #Before startFrame
    cmds.currentTime( startFrame - 1 )
    cmds.setAttr(obj+'.blendPoint1', 0 )
    cmds.setKeyframe(obj+'.blendPoint1' )
    #After startframe
    cmds.currentTime( startFrame )
    cmds.setAttr(obj+'.blendPoint1', 1 )
    cmds.setKeyframe(obj+'.blendPoint1' )
    #Before endframe
    cmds.currentTime( endFrame )
    cmds.setAttr(obj+'.blendPoint1', 1 )
    cmds.setKeyframe(obj+'.blendPoint1' )
    #After endframe
    cmds.currentTime( endFrame + 1 )
    cmds.setAttr(obj+'.blendPoint1', 0 )
    cmds.setKeyframe(obj+'.blendPoint1' )
    cmds.select(obj)

代码的问题是我冻结了控制器上的转换，将轴心设置为世界空间中的 (0,0,0)。解决此问题的最佳方法是创建一个临时定位器并让它跟随控制器。使用临时定位器的位置来创建控制器的运动路径。创建后删除临时定位器。

新代码

#
# This function creates an animation curve within the scene that follows the path of motion
# of the selected controller. It requires keyframe information in order to genereate the curve
# and uses the range of frames given by the user.
#
def createAnimCurve( bodyField, startField, endField, firstColor ):
    # Takes the value of the text field to select the controller
    obj = cmds.textField(bodyField, query=True, text=True)
    print obj
    # Takes in the string input of the paramter values and turns them into integer values
    startFrame = cmds.intField(startField, query=True, value=True)
    print startFrame
    endFrame = cmds.intField(endField, query=True, value=True)
    print endFrame
    color = cmds.colorIndexSliderGrp( firstColor, query=True, value=True ) - 1
    print color

    if obj == "":
        cmds.warning( "WARNING: Need to Select Body Part from Diagram" )
        return
    if cmds.objExists(obj[:-3]+'Path'):
        # Creates a warning pop up that double checks if the user wants to remove the curve
        delRes = cmds.confirmDialog( title='Delete Path Warning', message='Recreation will delete current path. Are you sure?', button=['Yes','No'], defaultButton='Yes', cancelButton='No', dismissString='No' )
        # If yes then the curve is deleted
        if delRes == 'Yes':
            cmds.delete(obj[:-3]+'Path')     
            cmds.delete(obj[:-3]+'Path_LOC')
        else:
            return
    # Sorts through the list of keyframes of the selected obj from the selected time line
    global keyframes
    keyframes = sorted(list(set(cmds.keyframe(obj, q=True, time=(startFrame,endFrame), timeChange=True))))
    # Creates the arrays for the required point positions
    points = []

    # Creates a temporary locator to find the world space values of the controller
    cmds.spaceLocator( n="tempLoc" )
    cmds.parentConstraint( obj, 'tempLoc', n='temp_PRT_CST' )

    #for step in range( startFrame, endFrame+2, int(curveCVstep)):
    for step in range(len(keyframes)):
        # Moves throughout the specified timeline to find point results
        cmds.currentTime( keyframes[step] )
        # Queries the position of the controller to draw the curve
        # Adds the position of the controller in world space to draw it relative to the control
        pos = cmds.xform( "tempLoc",q=True,ws=True,t=True )
        pos[0] = pos[0] 
        pos[1] = pos[1] 
        pos[2] = pos[2] 
        # convert the tuple (vector) to a string
        points.append(pos)
        print pos

    print "Creating the basic motion curve"
    cur = cmds.curve(d=2, ws=True, p=points, n=obj[:-3]+'Path')
    cmds.setAttr(cur + '.overrideEnabled', 1)
    cmds.setAttr(cur + '.overrideColor', color) 
    print cur
    cmds.move(points[0][0], points[0][1], points[0][2], cur+".scalePivot", cur+".rotatePivot", absolute=True)
    # command that runs through each cv of the curve and returns their position within a list.
    cvs = cmds.getAttr( obj[:-3]+'Path.cv[*]' )
    print cvs

    # Deletes the temp locator
    cmds.select("temp_PRT_CST")
    cmds.delete()
    cmds.select("tempLoc")
    cmds.delete()

    global initCVS
    initCVS = cvs
    # Create a locator for the motion path that the controller will now follow
    locate = cmds.spaceLocator( n=obj[:-3]+"Path_LOC" )
    #for step in range( startFrame, endFrame+2, int(curveCVstep)):
    for step in range(len(keyframes)):
        # Moves throughout the specified timeline to find point results
        cmds.currentTime( keyframes[step] )
        # Moves the locator to match the position of the controller
        cmds.move( cvs[step][0], cvs[step][1], cvs[step][2], locate)
        # Keyframes the locator
        cmds.setKeyframe( locate )
    # Position obj at the location of locate.
    cmds.pointConstraint( locate, obj, n=obj[:-3]+"LOC1_PNT" )
    # keys the weight of the point constraint to 0 before and after time frame (set to 1 during time frame)
    #Before startFrame
    cmds.currentTime( startFrame - 1 )
    cmds.setAttr(obj+'.blendPoint1', 0 )
    cmds.setKeyframe(obj+'.blendPoint1' )
    #After startframe
    cmds.currentTime( startFrame )
    cmds.setAttr(obj+'.blendPoint1', 1 )
    cmds.setKeyframe(obj+'.blendPoint1' )
    #Before endframe
    cmds.currentTime( endFrame )
    cmds.setAttr(obj+'.blendPoint1', 1 )
    cmds.setKeyframe(obj+'.blendPoint1' )
    #After endframe
    cmds.currentTime( endFrame + 1 )
    cmds.setAttr(obj+'.blendPoint1', 0 )
    cmds.setKeyframe(obj+'.blendPoint1' )
    cmds.select(obj)

生成的运动路径如下所示

以下是正确的弧线应该遵循的内容

这是基于新代码的新曲线。它似乎在沿着运动路径移动，但它被压缩了。

Answer 1

我刚刚想到的另一个想法是将临时定位器作为控件的父级（位于控件的枢轴处）。然后您可以使用定位器中的worldPosition xyz attr 值来绘制曲线点。得到曲线后可以删除定位器。

通过将定位器定位在控件的枢轴上以绘制曲线，它应该可以让您在没有太多麻烦的情况下进行约束（至少在理论上）。由于定位器已经具有“易于查询”的世界空间位置值，因此它的数学强度也较低。

当然它不像做所有的数学计算那么酷，但如果它有效......

Answer 2

如果你只是想获得某物的世界空间位置，你可以使用：

position = cmds.xform(item, q=True, ws=True, t=True)

然后根据需要使用该位置数据 - 无论父母如何旋转，它都应该工作... xform 命令也可用于设置世界空间中事物的位置：

cmds.xform(item, ws=True, t=position)

我不确定这是否真的回答了您的问题 - 有点不清楚您要在代码中实现什么；我不能完全理解打开/关闭定位器和点约束的原因。您是否尝试创建可编辑的运动轨迹？

如果是这样，您是否尝试过使用 Maya 内置的 editable motion trail 工具？

如果您出于某种原因尝试自己制作，我想您可以遵循“2 步”方法，首先创建一条曲线，其中每个 cv 通过您指定的起点位于控件的世界空间位置/时间结束。然后编辑曲线 cv 位置以清理圆弧并运行一个单独的函数来查询每个 cv 的世界空间位置，然后将它们应用于控件并在适当的时间设置关键帧。由于您是在世界空间位置执行所有这些操作，因此您无需担心任何父位置/旋转（幸运的是，这应该使代码相对简单）。