Mesh smoothing on a surface

"""Smooth a mesh on a NURBS surface.

- make a mesh datastructure form a given Rhino mesh
- define a target surface
- smooth the mesh
- use a callback to pull the mesh back onto the surface at every iteration
- visualize the process with a conduit

author : Tom Van Mele, Matthias Rippmann
email  :

from __future__ import print_function

from compas.datastructures import Mesh
from compas.geometry import smooth_area

import compas_rhino

from compas_rhino.helpers import mesh_from_guid

from compas_rhino.conduits import LinesConduit
from compas_rhino.geometry import RhinoSurface
from compas_rhino.artists import MeshArtist

# make a mesh datastructure from a Rhino mesh object
# and select a target surface

guid = compas_rhino.select_mesh()
mesh = mesh_from_guid(Mesh, guid)

guid = compas_rhino.select_surface()
surf = RhinoSurface(guid)

# extract the input for the smoothing algorithm from the mesh
# and identify the boundary as fixed

vertices  = mesh.get_vertices_attributes('xyz')
faces     = [mesh.face_vertices(fkey) for fkey in mesh.faces()]
adjacency = [mesh.vertex_faces(key, ordered=True) for key in mesh.vertices()]
fixed     = set(mesh.vertices_on_boundary())

# make a conduit for visualization
# and a callback for updating the conduit
# and for pulling the free vertices back to the surface
# at every iteration

edges = list(mesh.edges())
lines = [[vertices[u], vertices[v]] for u, v in edges]

conduit = LinesConduit(lines, refreshrate=5)

def callback(k, args):
    for index in range(len(vertices)):
        if index in fixed:
        x, y, z = surf.closest_point(vertices[index])
        vertices[index][0] = x
        vertices[index][1] = y
        vertices[index][2] = z

    conduit.lines = [[vertices[u], vertices[v]] for u, v in edges]

# with the conduit enabled
# run the smoothing algorithm
# update the mesh when smoothing is done
# and draw the result

with conduit.enabled():

for key, attr in mesh.vertices(True):
    attr['x'] = vertices[key][0]
    attr['y'] = vertices[key][1]
    attr['z'] = vertices[key][2]

artist = MeshArtist(mesh, layer='mesh-out')