i'm having another one of those api "what?!" moments. someone please
help me to understand what i'm doing wrong. i'm making a sphere and
trying to invert it's normals, but MFnMesh.setNormals seems to only
incrementally set the normals. each time i run it with the same set of
input normals and the normals get closer to the desired values without
ever actually getting set all the way.
import maya.cmds as cmds
import maya.mel as mel
import maya.OpenMaya as api
# make the sphere and get the MFn
mesh, h = cmds.polySphere( sa=10, sh=10 )
mel.eval( 'setPolygonDisplaySettings("vNormal")' )
mesh = cmds.listRelatives( mesh, s=1)[0]
sel = api.MSelectionList()
sel.add( mesh )
dag = api.MDagPath()
sel.getDagPath(0,dag)
meshFn = api.MFnMesh( dag )
# invert the vertex normals
normalArray = api.MFloatVectorArray()
newNormalArray = api.MFloatVectorArray()
meshFn.getNormals( normalArray, api.MSpace.kWorld )
for i in range( normalArray.length() ):
normal = normalArray[i]
newNormalArray.append( normal * -1 )
# set the new, inverted vertex normals
meshFn.setNormals( newNormalArray, api.MSpace.kWorld )
# new get the normals. they should be the same as what we just set,
right?
checkNormalArray = api.MFloatVectorArray()
meshFn.getNormals( checkNormalArray, api.MSpace.kWorld )
def angularDiff( arrayOne, arrayTwo ):
"add up the absolute angular difference between two vector arrays and
print it out"
sumAngles = 0.0
for i in range( arrayOne.length() ):
newNormal = arrayOne[i]
checkNormal = arrayTwo[i]
sumAngles += abs( newNormal.angle( checkNormal ) )
print sumAngles
angularDiff( newNormalArray, checkNormalArray)
# 227.588285092
meshFn.setNormals( newNormalArray, api.MSpace.kWorld )
meshFn.getNormals( checkNormalArray, api.MSpace.kWorld )
angularDiff( newNormalArray, checkNormalArray)
#11.7161702135
meshFn.setNormals( newNormalArray, api.MSpace.kWorld )
meshFn.getNormals( checkNormalArray, api.MSpace.kWorld )
angularDiff( newNormalArray, checkNormalArray)
#5.86650015175
meshFn.setNormals( newNormalArray, api.MSpace.kWorld )
meshFn.getNormals( checkNormalArray, api.MSpace.kWorld )
angularDiff( newNormalArray, checkNormalArray)
#2.94336352771
meshFn.setNormals( newNormalArray, api.MSpace.kWorld )
meshFn.getNormals( checkNormalArray, api.MSpace.kWorld )
angularDiff( newNormalArray, checkNormalArray)
#1.48185980244
i feel like i must be getting tripped up with c++ pointer methodology
in python somewhere but i can't see where. any help would be greatly
appreciated.
btw, this group is really growing into a great list. it's got a great
mixture of gurus and newbs all helping each other out in their various
areas of expertise. good stuff.
-chad
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Yours,
Maya-Python Club Team.
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