meshCurve

"""
Converts a polygon mesh to a first degree nurbs curve.
"""
from maya import cmds
import maya.api.OpenMaya as om2


def getSelectedMeshes():
    """
    Gets the currently selected mesh paths.

    Returns:
        list(MDagPath): A list of dag paths for the selected meshes.
    """
    sel = om2.MGlobal.getActiveSelectionList()
    selected = []
    for i in range(sel.length()):
        mObj, dagPath = sel.getDependNode(i), sel.getDagPath(i)
        if mObj.hasFn(om2.MFn.kMesh):
            selected.append(dagPath)
        for i in range(dagPath.childCount()):
            childObj = dagPath.child(i)
            if childObj.hasFn(om2.MFn.kMesh):
                selected.append(om2.MDagPath.getAPathTo(childObj))
    return selected


def getConnectedPoints(meshIt, index, indices=None, points=None):
    """
    A recursive function that iteratively returns a line of points connecting all vertices on a mesh.
    This function will

    Args:
        meshIt(MItMeshVertex): A mesh vertex iterator to use.
        index(index): The vertex index to find connected points for.
        indices(list): A list of connected vertex tuples that have been visited. Used to break recursion.
        points(list): An existing list of points to append to.

    Returns:
        set, list: A set of connected vertex tuples and a list of MPoints.
    """
    points = points or []
    indices = indices or set()

    # Add the current point
    meshIt.setIndex(index)
    points.append(meshIt.position(om2.MSpace.kWorld))

    for connectedIndex in meshIt.getConnectedVertices():
        # Skip visited points
        if (index, connectedIndex) in indices:
            continue
        if (connectedIndex, index) in indices:
            continue
            
        # Recursively add connected vertices
        indices.add((index, connectedIndex))
        indices, points = getConnectedPoints(
            meshIt, connectedIndex, indices, points
        )
        
        # Return the line of points to the current vertex
        meshIt.setIndex(index)
        points.append(meshIt.position(om2.MSpace.kWorld))

    return indices, points


def convertSelectedMesh():
    """ Converts the currently selected meshes to nurbs curves. """
    for meshDag in getSelectedMeshes():
        meshIt = om2.MItMeshVertex(meshDag)
        indices, points = getConnectedPoints(meshIt, 0)
        points = [om2.MVector(point) for point in points]
        cmds.curve(p=points, degree=1)