surfaces/surf/subd/cc.py

from collections import defaultdict

from surf.geometry import PolygonMesh, centroid

from pprint import pprint as pp   # XXX


def refine(mesh):
    new_vertices = list(mesh.vertices)
    f_vert_offset = len(new_vertices)

    edge_vids_for = defaultdict(list)
    face_vids_for = defaultdict(list)

    new_edges = list(mesh.edges)
    new_faces = []

    # For each face, add a face point
    for cur_face_id, cur_face in enumerate(mesh.faces):
        # Set each face point to be the centroid of all original points for the
        # respective face.

        # here we have already created a list that is a copy of the original
        # verts. we append the new face points to that same list, and simply
        # keep track of offsets into the new vert list ... see e_vert_offset
        # below
        new_face_point = mesh.centroid(cur_face)
        new_vertices.append(new_face_point)

    e_vert_offset = len(new_vertices)

    # For each edge, add an edge point.
    for cur_edge_id, cur_edge in enumerate(mesh.edges):
        # make mapping from edge -> new_face_vert for later
        face_ids_for_edge = mesh.faces_for_edge[cur_edge_id]
        for fid in face_ids_for_edge:
            edge_vids_for[fid].append(cur_edge_id)

        tmp_verts = []

        # Set each edge point to be the average of the two neighbouring, (very
        # recently calculated) face points ...
        tmp_verts.extend([new_vertices[f + f_vert_offset] for f in face_ids_for_edge])
        
        # ... and its two original endpoints.
        tmp_verts.extend([mesh.vertices[vid] for vid in cur_edge])

        # centroid == average
        new_vertices.append(centroid(tmp_verts))

    # For each face point, add an edge for every edge of the face, connecting
    # the face point to each edge point for the face.
    for trunc_vid in xrange(len(new_vertices[f_vert_offset:e_vert_offset])):
        overall_vid = f_vert_offset + trunc_vid
        for edge_vid in edge_vids_for[trunc_vid]:
            new_edges.append([edge_vid, overall_vid])

    # pp(new_edges)

    # For each original point P
    assert f_vert_offset == len(mesh.vertices)
    for new_vid in xrange(f_vert_offset):
        # take the average F of all n face points for faces touching P ...
        F = centroid([mesh.vertices[vid] for vid in mesh.faces_for_vert[new_vid]])
        print ">>>", F

        # and take the average R of all n edge midpoints for edges touching P
        # wiki is wrong ... it should be the edge points, not midpoints ...
        edges = [mesh.edges[eid] for eid in mesh.edges_for_vert[new_vid]]
        e_verts = []
        for edge in edges:
            e_verts.extend([mesh.vertices[vid] for vid in edge])

        R = centroid(e_verts)
        # where each edge midpoint is the average of its two endpoint vertices.
        # Move each original point to the point (or add it to new_verts)
        v = (F + 2 * R + (len(edges) - 3) * new_vertices[new_vid]) / len(edges)

    return None



if __name__ == '__main__':
    import json
    from surf.geometry import PolygonMesh
    from surf.subd.cc import refine


    cube = json.load(open('blender/samples/cube.json', 'r'))
    p = PolygonMesh(**cube)
    q = refine(p)