Gets mesh and and an index of a polygon that is under the mouse in MODO viewport.

getPolyUnderMouse.py

# python

import lx
import modo

# This snippet queries polygon that is under a mouse.

# Querying polygon only works correctly on active meshes.
# That means that if mouse is over the mesh that is not active
# (was not selected prior to entering component mode),
# the query returns None.
# To make the query work on any mesh we will do 2 queries.
#
# We will query for the item under the mouse first.
# If this one is None then we know we're not over any polygon either.
# 
# Then we query for polygon. If it's None then it means we're not over the active mesh.
# So we force select the mesh we're over to make sure it becomes the active one.
# Then we query for the polygon again.
#
# This time we can be sure that
# it will not return None if we are in fact over a polygon.
# POLY query returns a string in format:  mesh_index,polygon_index
# So you need to parse that string to extract index integers.
# It is also possible to get multiple polygons if you have more then one active
# mesh or you're over an edge that belongs to 2 polygons.
# In such case you will get a tuple of strings and polygons are ordered by depth
# (closest one is first).

def polygonUnderMouse():
	itemId = lx.eval("query view3dservice element.over ? ITEM")
	if itemId is None:
		lx.out("Mouse is not over any items.")
		return

	scene = modo.Scene()
	item = scene.item(itemId)

	p = lx.eval("query view3dservice element.over ? POLY")
	if p is None:
		# We're over a mesh but it's not active one so poly query returns None.
		scene.select(item)
		p = lx.eval("query view3dservice element.over ? POLY")

	if p is None:
		lx.out("Cannot find polygon under the mouse.")
		return

	if not isinstance(p, tuple):
		p = [p]
	pIndex = int(p[0].split(',')[1])

	lx.out("Polygon under mouse: %s - %d" % (item.name, pIndex))

polygonUnderMouse()