352 lines
11 KiB
Python
352 lines
11 KiB
Python
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"""
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repair.py
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-------------
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Fill holes and fix winding and normals of meshes.
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"""
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import numpy as np
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from . import graph
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from . import triangles
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from .constants import log
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from .grouping import group_rows
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from .geometry import faces_to_edges
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try:
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import networkx as nx
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except BaseException as E:
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# create a dummy module which will raise the ImportError
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# or other exception only when someone tries to use networkx
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from .exceptions import ExceptionModule
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nx = ExceptionModule(E)
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def fix_winding(mesh):
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"""
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Traverse and change mesh faces in-place to make sure winding
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is correct, with edges on adjacent faces in
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opposite directions.
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Parameters
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-------------
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mesh: Trimesh object
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Alters
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-------------
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mesh.face: will reverse columns of certain faces
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"""
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# anything we would fix is already done
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if mesh.is_winding_consistent:
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return
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graph_all = nx.from_edgelist(mesh.face_adjacency)
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flipped = 0
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faces = mesh.faces.view(np.ndarray).copy()
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# we are going to traverse the graph using BFS
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# start a traversal for every connected component
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for components in nx.connected_components(graph_all):
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# get a subgraph for this component
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g = graph_all.subgraph(components)
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# get the first node in the graph in a way that works on nx's
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# new API and their old API
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start = next(iter(g.nodes()))
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# we traverse every pair of faces in the graph
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# we modify mesh.faces and mesh.face_normals in place
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for face_pair in nx.bfs_edges(g, start):
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# for each pair of faces, we convert them into edges,
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# find the edge that both faces share and then see if edges
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# are reversed in order as you would expect
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# (2, ) int
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face_pair = np.ravel(face_pair)
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# (2, 3) int
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pair = faces[face_pair]
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# (6, 2) int
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edges = faces_to_edges(pair)
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overlap = group_rows(np.sort(edges, axis=1),
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require_count=2)
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if len(overlap) == 0:
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# only happens on non-watertight meshes
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continue
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edge_pair = edges[overlap[0]]
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if edge_pair[0][0] == edge_pair[1][0]:
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# if the edges aren't reversed, invert the order of one face
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flipped += 1
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faces[face_pair[1]] = faces[face_pair[1]][::-1]
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if flipped > 0:
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mesh.faces = faces
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log.debug('flipped %d/%d edges', flipped, len(mesh.faces) * 3)
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def fix_inversion(mesh, multibody=False):
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"""
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Check to see if a mesh has normals pointing "out."
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Parameters
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-------------
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mesh: Trimesh object
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multibody: bool, if True will try to fix normals on every body
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Alters
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-------------
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mesh.face: may reverse faces
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"""
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if multibody:
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groups = graph.connected_components(mesh.face_adjacency)
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# escape early for single body
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if len(groups) == 1:
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if mesh.volume < 0.0:
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mesh.invert()
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return
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# mask of faces to flip
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flip = np.zeros(len(mesh.faces), dtype=np.bool)
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# save these to avoid thrashing cache
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tri = mesh.triangles
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cross = mesh.triangles_cross
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# indexes of mesh.faces, not actual faces
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for faces in groups:
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# calculate the volume of the submesh faces
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volume = triangles.mass_properties(
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tri[faces],
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crosses=cross[faces],
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skip_inertia=True)['volume']
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# if that volume is negative it is either
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# inverted or just total garbage
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if volume < 0.0:
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flip[faces] = True
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# one or more faces needs flipping
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if flip.any():
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with mesh._cache:
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# flip normals of necessary faces
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if 'face_normals' in mesh._cache:
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mesh.face_normals[flip] *= -1.0
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# flip faces
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mesh.faces[flip] = np.fliplr(mesh.faces[flip])
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# save wangled normals
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mesh._cache.clear(exclude=['face_normals'])
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elif mesh.volume < 0.0:
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# reverse every triangles and flip every normals
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mesh.invert()
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def fix_normals(mesh, multibody=False):
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"""
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Fix the winding and direction of a mesh face and
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face normals in-place.
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Really only meaningful on watertight meshes but will orient all
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faces and winding in a uniform way for non-watertight face
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patches as well.
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Parameters
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-------------
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mesh : trimesh.Trimesh
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Mesh to fix normals on
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multibody : bool
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if True try to correct normals direction
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on every body rather than just one
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Alters
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--------------
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mesh.faces
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Will flip columns on inverted faces
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"""
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# traverse face adjacency to correct winding
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fix_winding(mesh)
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# check to see if a mesh is inverted
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fix_inversion(mesh, multibody=multibody)
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def broken_faces(mesh, color=None):
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"""
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Return the index of faces in the mesh which break the
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watertight status of the mesh.
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Parameters
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--------------
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mesh: Trimesh object
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color: (4,) uint8, will set broken faces to this color
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None, will not alter mesh colors
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Returns
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---------------
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broken: (n, ) int, indexes of mesh.faces
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"""
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adjacency = nx.from_edgelist(mesh.face_adjacency)
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broken = [k for k, v in dict(adjacency.degree()).items()
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if v != 3]
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broken = np.array(broken)
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if color is not None and broken.size != 0:
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# if someone passed a broken color
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color = np.array(color)
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if not (color.shape == (4,) or color.shape == (3,)):
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color = [255, 0, 0, 255]
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mesh.visual.face_colors[broken] = color
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return broken
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def fill_holes(mesh):
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"""
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Fill single- triangle holes on triangular meshes by adding
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new triangles to fill the holes. New triangles will have
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proper winding and normals, and if face colors exist the color
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of the last face will be assigned to the new triangles.
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Parameters
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---------
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mesh : trimesh.Trimesh
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Mesh will be repaired in- place
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"""
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def hole_to_faces(hole):
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"""
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Given a loop of vertex indices representing a hole, turn it into
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triangular faces.
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If unable to do so, return None
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Parameters
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---------
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hole: ordered loop of vertex indices
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Returns
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---------
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(n, 3) new faces
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(m, 3) new vertices
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"""
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hole = np.asanyarray(hole)
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# the case where the hole is just a single missing triangle
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if len(hole) == 3:
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return [hole], []
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# the hole is a quad, which we fill with two triangles
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if len(hole) == 4:
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face_A = hole[[0, 1, 2]]
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face_B = hole[[2, 3, 0]]
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return [face_A, face_B], []
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return [], []
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if len(mesh.faces) < 3:
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return False
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if mesh.is_watertight:
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return True
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# we know that in a watertight mesh every edge will be included twice
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# thus every edge which appears only once is part of a hole boundary
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boundary_groups = group_rows(
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mesh.edges_sorted, require_count=1)
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# mesh is not watertight and we have too few edges
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# edges to do a repair
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# since we haven't changed anything return False
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if len(boundary_groups) < 3:
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return False
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boundary_edges = mesh.edges[boundary_groups]
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index_as_dict = [{'index': i} for i in boundary_groups]
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# we create a graph of the boundary edges, and find cycles.
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g = nx.from_edgelist(
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np.column_stack((boundary_edges,
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index_as_dict)))
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cycles = np.array(nx.cycle_basis(g))
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new_faces = []
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new_vertex = []
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for hole in cycles:
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# convert the hole, which is a polygon of vertex indices
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# to triangles and new vertices
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faces, vertex = hole_to_faces(hole=hole)
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if len(faces) == 0:
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continue
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# remeshing returns new vertices as negative indices, so change those
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# to absolute indices which won't be screwed up by the later appends
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faces = np.array(faces)
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faces[faces < 0] += len(new_vertex) + len(mesh.vertices) + len(vertex)
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new_vertex.extend(vertex)
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new_faces.extend(faces)
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new_faces = np.array(new_faces)
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new_vertex = np.array(new_vertex)
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if len(new_faces) == 0:
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# no new faces have been added, so nothing further to do
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# the mesh is NOT watertight, as boundary groups exist
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# but we didn't add any new faces to fill them in
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return False
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for face_index, face in enumerate(new_faces):
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# we compare the edge from the new face with
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# the boundary edge from the source mesh
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edge_test = face[0:2]
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edge_boundary = mesh.edges[g.get_edge_data(*edge_test)['index']]
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# in a well construtced mesh, the winding is such that adjacent triangles
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# have reversed edges to each other. Here we check to make sure the
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# edges are reversed, and if they aren't we simply reverse the face
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reversed = edge_test[0] == edge_boundary[1]
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if not reversed:
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new_faces[face_index] = face[::-1]
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# stack vertices into clean (n, 3) float
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if len(new_vertex) != 0:
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new_vertices = np.vstack((mesh.vertices, new_vertex))
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else:
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new_vertices = mesh.vertices
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# try to save face normals if we can
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if 'face_normals' in mesh._cache.cache:
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cached_normals = mesh._cache.cache['face_normals']
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else:
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cached_normals = None
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# also we can remove any zero are triangles by masking here
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new_normals, valid = triangles.normals(new_vertices[new_faces])
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# all the added faces were broken
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if not valid.any():
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return False
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# this is usually the case where two vertices of a triangle are just
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# over tol.merge apart, but the normal calculation is screwed up
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# these could be fixed by merging the vertices in question here:
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# if not valid.all():
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if mesh.visual.defined and mesh.visual.kind == 'face':
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color = mesh.visual.face_colors
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else:
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color = None
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# apply the new faces and vertices
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mesh.faces = np.vstack((mesh._data['faces'], new_faces[valid]))
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mesh.vertices = new_vertices
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# dump the cache and set id to the new hash
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mesh._cache.verify()
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# save us a normals recompute if we can
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if cached_normals is not None:
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mesh.face_normals = np.vstack((cached_normals,
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new_normals))
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# this is usually the case where two vertices of a triangle are just
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# over tol.merge apart, but the normal calculation is screwed up
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# these could be fixed by merging the vertices in question here:
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# if not valid.all():
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if color is not None:
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# if face colors exist, assign the last face color to the new faces
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# note that this is a little cheesey, but it is very inexpensive and
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# is the right thing to do if the mesh is a single color.
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color_shape = np.shape(color)
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if len(color_shape) == 2:
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new_colors = np.tile(color[-1], (np.sum(valid), 1))
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new_colors = np.vstack((color,
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new_colors))
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mesh.visual.face_colors = new_colors
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log.debug('Filled in mesh with %i triangles', np.sum(valid))
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return mesh.is_watertight
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