Maya: Highlight Tool

mht.py

import pymel
import traceback

def place_highlight(cam, obj):
    """ Creates a highlight rig for placing highlights on an object
    """
    
    parent_loc = pymel.core.spaceLocator()
    up_vector = pymel.core.spaceLocator()
    aim_loc = pymel.core.spaceLocator()
    vector01 = pymel.core.spaceLocator()
    vector02 = pymel.core.spaceLocator()
    highlight_loc = pymel.core.spaceLocator()
    highlight = pymel.core.polyPlane()[0]
    
    pymel.core.parent(up_vector, parent_loc)
    pymel.core.parent(aim_loc, parent_loc)
    pymel.core.parent(vector01, parent_loc)
    pymel.core.parent(vector02, parent_loc)
    pymel.core.parent(highlight_loc, parent_loc)
    pymel.core.parent(highlight, highlight_loc)

    for node in [up_vector, aim_loc, vector01, vector02, highlight_loc]:
        node.getShape().localScaleX.set(0)
        node.getShape().localScaleY.set(0)
        node.getShape().localScaleZ.set(0)

    up_vector.ty.set(1)
    vector01.tx.set(1)
    vector02.tx.set(1)
    highlight.tx.set(10)
    highlight.rz.set(90)
    highlight.primaryVisibility.set(0)
    
    pymel.core.normalConstraint(obj, parent_loc)
    pymel.core.geometryConstraint(obj, parent_loc)
    pymel.core.parentConstraint(aim_loc, vector02, maintainOffset=True)
    pymel.core.aimConstraint(cam, aim_loc, worldUpObject=up_vector)
    
    angle_between = pymel.core.createNode('angleBetween')
    uc01 = pymel.core.createNode('unitConversion')
    uc02 = pymel.core.createNode('unitConversion')
    md = pymel.core.createNode('multiplyDivide')
    
    uc01.conversionFactor.set(57.296)
    uc02.conversionFactor.set(0.017)
    md.operation.set(1)
    md.input2X.set(-1)
    md.input2Y.set(-1)
    md.input2Z.set(-1)
    
    vector01.translate >> angle_between.vector1
    vector02.translate >> angle_between.vector2
    angle_between.euler >> uc01.input
    uc01.output >> md.input1
    md.output >> uc02.input
    uc02.output >> highlight_loc.rotate
    
    mat = pymel.core.shadingNode("surfaceShader", asShader=True)
    shader = pymel.core.sets( renderable=True, noSurfaceShader=True, empty=True)
    mat.outColor.set([1, 1, 1])
    
    mat.outColor >> shader.surfaceShader
    
    pymel.core.sets(shader, edit=True, forceElement=[highlight])

cam = None
obj = None
for node in pymel.core.ls(selection=True):
    if node.getShape().nodeType() == 'camera':
        cam = node
    if node.getShape().nodeType() == 'mesh':
        obj = node

if not cam:
    pymel.core.error('No camera found in selection!')

if not obj:
    pymel.core.error('No meshes found in selection!')

try:
    place_highlight(cam, obj)
except:
    print traceback.format_exc()