Maya get closest vertex

getClosestVertex.py

import maya.api.OpenMaya as om
import maya.cmds as cmds

#returns the closest vertex given a mesh and a position [x,y,z] in world space.
#Uses om.MfnMesh.getClosestPoint() returned face ID and iterates through face's vertices.
def getClosestVertex(mayaMesh,pos=[0,0,0]):
    mVector = om.MVector(pos)#using MVector type to represent position
    selectionList = om.MSelectionList()
    selectionList.add(mayaMesh)
    dPath= selectionList.getDagPath(0)
    mMesh=om.MFnMesh(dPath)
    ID = mMesh.getClosestPoint(om.MPoint(mVector),space=om.MSpace.kWorld)[1] #getting closest face ID
    list=cmds.ls( cmds.polyListComponentConversion (mayaMesh+'.f['+str(ID)+']',ff=True,tv=True),flatten=True)#face's vertices list
    #setting vertex [0] as the closest one
    d=mVector-om.MVector(cmds.xform(list[0],t=True,ws=True,q=True))
    smallestDist2=d.x*d.x+d.y*d.y+d.z*d.z #using distance squared to compare distance
    closest=list[0]
    #iterating from vertex [1]
    for i in range(1,len(list)) :
        d=mVector-om.MVector(cmds.xform(list[i],t=True,ws=True,q=True))
        d2=d.x*d.x+d.y*d.y+d.z*d.z
        if d2<smallestDist2:
            smallestDist2=d2
            closest=list[i]      
    return closest

What if several closest faces are at the same distance? What if several vertices of the face are at the same distance?
It seems to implicitly choose the one with the lowest id in both cases while I would expect to get a list.

You're right. According to the documentation, it seems that MFnMesh.getClosestPoint() can't return a list of point plus face ID tuple. This is one limitation using this technique.

Thanks - saved me some time to quickly test a thing.

Here's a quick cleanup/rewrite as thanks!

from maya import cmds
import maya.api.OpenMaya as om
import operator


def getClosestVertex(mesh, pos=(0,0,0)):
    """Return closest vertex and distance from mesh to world-space position [x, y, z].
        
    Uses om.MfnMesh.getClosestPoint() returned face ID and iterates through face's vertices.
    
    Example:
        >>> getClosestVertex("pCube1", pos=[0.5, 0.5, 0.5])
        # (3, 0.0)
        >>> getClosestVertex("pCube1", pos=[0.5, 0.9, 0.5])
        # (3, 0.4)

    Args:
        mesh (str): Mesh node name.
        pos (list): Position vector XYZ
        
    Returns:
        tuple: (vertex index, distance)
    
    """
    pos = om.MPoint(pos)
    sel = om.MSelectionList()
    sel.add(mesh)
    fn_mesh = om.MFnMesh(sel.getDagPath(0))
    
    index = fn_mesh.getClosestPoint(pos, space=om.MSpace.kWorld)[1]  # closest polygon index    
    face_vertices = fn_mesh.getPolygonVertices(index)  # get polygon vertices
    
    vertex_distances = ((vertex, fn_mesh.getPoint(vertex, om.MSpace.kWorld).distanceTo(pos)) 
                         for vertex in face_vertices)
    return min(vertex_distances, key=operator.itemgetter(1))