angle measure construction script that show angle in real time between two vectors

angleMeasure

'''
Select three components and run the script.
Remember that selection order matters, so the second one will display the angle between 1-2 vector and 2-3 vector.
'''
import maya.cmds as mc
# make sure that tracking of selection order is turned on
if not mc.selectPref( q=1, trackSelectionOrder=1 ):
	mc.selectPref( trackSelectionOrder=1 )
# get ordered component selection
objs = mc.ls( os=1, fl=1 )
# script will work if there are only three components selected
if len( objs ) == 3:
	# create locators from selection objects
	grps = []
	decs = []
	for o in objs:
		# create empty group
		grp = mc.group( em=1, n= o + '_grp' )
		# edit group visibility by turning on its handle 
		mc.setAttr( grp + '.displayHandle', 1 )
		# replace the selection with component and appropriate component
		mc.select( o, r=1 )
		mc.select( grp, add=1 )
		# create pointOnPolyConstraint so each empty group will follow to appropriate component
		pCon = mc.pointOnPolyConstraint()
		# create decompose matrix and connect it to the worl space matrix of the empty group
		dec = mc.createNode( 'decomposeMatrix' )
		mc.connectAttr( grp + '.worldMatrix', dec + '.inputMatrix' )
		# add decompose matrix name for the further manipulations
		decs.append( dec )
		# store the second group name so it will drive angle annotation position
		if o == objs[1]:
			grps = grp
	# store two pairs of decompose matrices
	pairs = [ (decs[0],decs[1]), (decs[2],decs[1]) ]
	# create angle node that will output angle between two vectors: vector1( selection1-selection2 ) and vector2( selection3-selection2 )
	angle = mc.createNode( 'angleBetween' )
	# since we know that we have only two pairs we just iterate through both of them
	for k in xrange(2):
		# create distance node in order to connect to the pairs of decompose matrix of every pair of empty groups
		dim = mc.createNode('distanceDimShape')
		mc.connectAttr( pairs[k][0] + '.outputTranslate', dim + '.startPoint' )
		mc.connectAttr( pairs[k][1] + '.outputTranslate', dim + '.endPoint' )
		# add PlusMinusAverage node for extracting vector from selection1-selection2 and selection3-selection2
		pma = mc.createNode( 'plusMinusAverage' )
		# set Subtract operation of the PMA node
		mc.setAttr( pma + '.operation', 2 )
		mc.connectAttr( pairs[k][0] + '.outputTranslate', pma + '.input3D[0]' )
		mc.connectAttr( pairs[k][1] + '.outputTranslate', pma + '.input3D[1]' )
		# connect PMA vector output to appropriate input in angleBetween node
		mc.connectAttr( pma + '.output3D',  angle + '.vector' + str(k+1) )
	# now angleBetween node calculate angle between two vectors, let's add a node (in my case it is a particle node) that will show that value in viewport
	part = mc.particle( p=(0,0,0) )
	# add custom double type attribute that will receive angle value from angleBetween node
	mc.addAttr( part[-1], ln='angle', at='double' )
	mc.setAttr( part[-1] + '.particleRenderType', 2)
	# add boring stuff to connect custom attribute to displayed one
	mc.connectAttr( angle + '.axisAngle.angle', part[-1] + '.angle' )
	mc.addAttr( part[-1], ln='pointSize', at='long', min=1, max=60, dv=2 )
	mc.addAttr( part[-1], ln='selectedOnly', at='bool', dv=0 )
	mc.addAttr( part[-1], dt='string', ln='attributeName' )
	# tell particle node which attribute we want to display
	mc.setAttr( part[-1] + '.attributeName', 'angle' , type='string' )
	# change our attribute default color to yellow one
	mc.setAttr( part[-1] + '.overrideEnabled', 1 )
	mc.setAttr( part[-1] + '.overrideRGBColors', 1 )
	mc.setAttr( part[-1] + '.overrideColorR', 1 )
	mc.setAttr( part[-1] + '.overrideColorG', 1 )
	mc.setAttr( part[-1] + '.overrideColorB', 0.2 )
	# connect position of the particle notation node to the second group, so it will show the angle right on place
	mc.connectAttr( grps + '.translate', part[0] + '.translate' )