findNumOfMeshIslands.py

import maya.OpenMaya as om
import pprint
import cProfile

selList = om.MSelectionList()

# selList.add('test_num_of_mesh_shells:pCubeShape1')
selList.add('test_num_of_mesh_shells:pSphereShape1')

# selList.add('theCubeShape')

node = om.MObject()

selList.getDependNode(0, node)


def findNumOfMeshShells(node):
    """
    This function finds the number of isolated mesh islands there are under
    a given shape **node**.

    Args:
        node (MObject): The node representing the DAG shape node to find the
            number of mesh islands for.

    Returns:
        (int): The number of mesh islands.
    """
    # Sanity checks
    if node.isNull():
        raise RuntimeError('The internal Maya Object represented by this node '
                           'does not exist!')
    if node.apiType() != om.MFn.kMesh:
        raise TypeError('The **node** given does not represent a Maya mesh shape!')

    faceConnectionMappings = {}

    itMeshPoly = om.MItMeshPolygon(node)

    while not itMeshPoly.isDone():
        try:
            currentFaceIdx = itMeshPoly.index()
            connectedFaceIdxs = om.MIntArray()
            itMeshPoly.getConnectedFaces(connectedFaceIdxs)

            faceConnectionMappings[currentFaceIdx] = [connectedFaceIdxs[idx]
                                            for idx in xrange(connectedFaceIdxs.length())]

            itMeshPoly.next()
        except RuntimeError as err:
            print "failed to iterate"
            break

    trees = {}
    visitedNodes = []

    for faceIdx, connectedFacesIdxs in faceConnectionMappings.iteritems():
        if faceIdx in visitedNodes:
            continue
        visitedNodes.append(faceIdx)

        if len(connectedFacesIdxs) == 0:
            trees[faceIdx] = []
        else:
            trees[faceIdx] = connectedFacesIdxs

            for idx in connectedFacesIdxs:
                if idx in visitedNodes:
                    continue
                for c_idx in faceConnectionMappings.get(idx, []):
                    if c_idx in visitedNodes:
                        continue
                    if c_idx not in trees[faceIdx]:
                        trees[faceIdx].append(c_idx)

                visitedNodes.append(idx)

    return len(trees.keys())


print findNumOfMeshShells(node)
cProfile.run('findNumOfMeshShells(node)')