Add triangulated flag to Mesh.to_vertices_and_faces and also Shape's abstract method

Author: gonzalocasas

CHANGELOG.md

@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+* Added optional `triangulated` flag to `Mesh.to_vertices_and_faces`.
+
 ### Changed
 
 ### Removed

src/compas/datastructures/mesh/mesh.py

@@ -473,9 +473,14 @@ def from_vertices_and_faces(cls, vertices, faces):
 
         return mesh
 
-    def to_vertices_and_faces(self):
+    def to_vertices_and_faces(self, triangulated=False):
         """Return the vertices and faces of a mesh.
 
+        Parameters
+        ----------
+        triangulated: bool, optional
+            If True, triangulate the faces.
+
         Returns
         -------
         list[list[float]]
@@ -486,7 +491,36 @@ def to_vertices_and_faces(self):
         """
         key_index = self.key_index()
         vertices = [self.vertex_coordinates(key) for key in self.vertices()]
-        faces = [[key_index[key] for key in self.face_vertices(fkey)] for fkey in self.faces()]
+
+        if not triangulated:
+            faces = [[key_index[key] for key in self.face_vertices(fkey)] for fkey in self.faces()]
+            return vertices, faces
+
+        faces = []
+
+        for fkey in self.faces():
+            face_vertices = self.face_vertices(fkey)
+
+            if len(face_vertices) == 3:
+                a, b, c = face_vertices
+                faces.append([key_index[a], key_index[b], key_index[c]])
+            elif len(face_vertices) == 4:
+                a, b, c, d = face_vertices
+                faces.append([key_index[a], key_index[b], key_index[c]])
+                faces.append([key_index[a], key_index[c], key_index[d]])
+            else:
+                centroid = centroid_polygon([self.vertex_coordinates(key) for key in face_vertices])
+                vertices.append(centroid)
+                vcount = len(vertices)
+
+                for i in range(len(face_vertices) - 1):
+                    a, b, c = face_vertices[i], face_vertices[i + 1], vcount - 1
+                    faces.append([key_index[a], key_index[b], c])
+
+                # last face between first, last and centroid
+                a, b, c = face_vertices[0], face_vertices[-1], vcount - 1
+                faces.append([key_index[b], key_index[a], c])
+
         return vertices, faces
 
     @classmethod

src/compas/geometry/shapes/_shape.py

@@ -10,7 +10,7 @@ class Shape(Geometry):
     """Base class for geometric shapes."""
 
     @abc.abstractmethod
-    def to_vertices_and_faces(self):
+    def to_vertices_and_faces(self, triangulated=False):
         pass
 
     def __add__(self, other):

tests/compas/datastructures/test_mesh.py

@@ -1,3 +1,4 @@
+from pickle import TRUE
 import tempfile
 
 import pytest
@@ -7,6 +8,7 @@
 from compas.datastructures import meshes_join_and_weld
 from compas.geometry import Box
 from compas.geometry import Polygon
+from compas.geometry import Polyhedron
 from compas.geometry import Translation
 from compas.geometry import allclose
 
@@ -183,6 +185,25 @@ def test_to_vertices_and_faces():
     assert len(faces) == 25
 
 
+def test_to_vertices_and_faces_triangulated():
+    # tri
+    mesh = Mesh.from_shape(Polyhedron.from_platonicsolid(4))
+    vertices, faces = mesh.to_vertices_and_faces(triangulated=True)
+    assert len(vertices) == 4
+    assert len(faces) == 4
+
+    # quad
+    mesh = Mesh.from_shape(Polyhedron.from_platonicsolid(6))
+    vertices, faces = mesh.to_vertices_and_faces(triangulated=True)
+    assert len(vertices) == 8
+    assert len(faces) == 12
+
+    # ngon
+    mesh = Mesh.from_shape(Polyhedron.from_platonicsolid(12))
+    vertices, faces = mesh.to_vertices_and_faces(triangulated=True)
+    assert len(vertices) == 32
+    assert len(faces) == 60
+
 # --------------------------------------------------------------------------
 # helpers
 # --------------------------------------------------------------------------