A Formula or a Command to find out the Face-number based on first vertex-num provided

Coding
1

I am looking for a formula or a command (OpenMaya or Python or Mel) to which if I provide the vertex number, it returns me the face number of the mesh considering provided vertex number is the first vertex of a Mesh.
(I believe I will have to provide mesh name because this calculation will need mesh width and height)

Note : I have to do the calculation based on Vertex Number, I can’t use FaceVertex number.


eg. In the attached image :
vertex - 0 gives Face - 0
vertex - 1 gives Face - 1
vertex - 3 gives Face - 2
vertex - 4 gives Face - 3

Thanks

2

Hey Chakmangoo,

You can use the mel commands below to get what you need :slight_smile:

Use:

polyInfo -vertexToFace

to get a list of faces that use the vert, then use

polyInfo -faceToVertex

for each face and check the first vertex in the results…

Maya returns the vert list of a face in winding order, so you will get the correct order.

If you need a hand getting the code going, drop me a line.

-Butters

3

Hello Butters,

Thanks for your help. I forgot to mention that I am writing the code in OpenMaya.

I came up with following function which gives me the mapping :

def mapVertexTofaceandFaceVertex(objName):
dagNode = nameToMObjectName(objName)
dagPath = mObjectNameToDagPath(dagNode)
mFnMesh = OpenMaya.MFnMesh(dagPath)
mFnDagNode = OpenMaya.MFnDagNode(dagNode)

mColorArray = OpenMaya.MColorArray()
mFnMesh.getVertexColors(mColorArray)


validVertices = []
for i in range(0, mColorArray.length()):
	bBox = mFnDagNode.boundingBox()
	if (i % (bBox.width() + 1)):
		validVertices.append(i - 1)

''' Find number of Faces in Mesh '''
mFaceColorArray = OpenMaya.MColorArray()
mFnMesh.getFaceVertexColors(mFaceColorArray)
totalFaces = mFaceColorArray.length() / 4

faceVertexMap = []

faceNumbers = []
firstVertex = []
firstFaceVertex = []

faceVertexCounter = 0
for i in range(0, totalFaces):
	faceVertexMap.append({"face":i, "firstVertex":validVertices[i], "faceVertex":faceVertexCounter})
	faceNumbers.append(i)
	firstVertex.append(validVertices[i])
	firstFaceVertex.append(faceVertexCounter)
	
	faceVertexCounter += 4
	#faceVertexMap.append(validVertices[i])
	
return 	faceNumbers, firstVertex, firstFaceVertex

[QUOTE=Butters;16922]Hey Chakmangoo,

You can use the mel commands below to get what you need :slight_smile:

Use:

polyInfo -vertexToFace

to get a list of faces that use the vert, then use

polyInfo -faceToVertex

for each face and check the first vertex in the results…

Maya returns the vert list of a face in winding order, so you will get the correct order.

If you need a hand getting the code going, drop me a line.

-Butters[/QUOTE]

4

Nice work dude!