Fix #1040. New utility for geometric shape analysis only requiring numpy.

src/ifcopenshell-python/ifcopenshell/util/shape.py

@@ -0,0 +1,182 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2023 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+import numpy as np
+
+tol = 1e-6
+
+
+def is_x(value, x):
+    return abs(x - value) < tol
+
+
+def get_volume(geometry):
+    def signed_triangle_volume(p1, p2, p3):
+        v321 = p3[0] * p2[1] * p1[2]
+        v231 = p2[0] * p3[1] * p1[2]
+        v312 = p3[0] * p1[1] * p2[2]
+        v132 = p1[0] * p3[1] * p2[2]
+        v213 = p2[0] * p1[1] * p3[2]
+        v123 = p1[0] * p2[1] * p3[2]
+        return (1.0 / 6.0) * (-v321 + v231 + v312 - v132 - v213 + v123)
+
+    verts = geometry.verts
+    faces = geometry.faces
+    grouped_verts = [[verts[i], verts[i + 1], verts[i + 2]] for i in range(0, len(verts), 3)]
+    volumes = [
+        signed_triangle_volume(grouped_verts[faces[i]], grouped_verts[faces[i + 1]], grouped_verts[faces[i + 2]])
+        for i in range(0, len(faces), 3)
+    ]
+    return abs(sum(volumes))
+
+
+def get_x(geometry):
+    x_values = [geometry.verts[i] for i in range(0, len(geometry.verts), 3)]
+    return max(x_values) - min(x_values)
+
+
+def get_y(geometry):
+    y_values = [geometry.verts[i + 1] for i in range(0, len(geometry.verts), 3)]
+    return max(y_values) - min(y_values)
+
+
+def get_z(geometry):
+    z_values = [geometry.verts[i + 2] for i in range(0, len(geometry.verts), 3)]
+    return max(z_values) - min(z_values)
+
+
+def get_area_vf(vertices, faces):
+    # Calculate the triangle normal vectors
+    v1 = vertices[faces[:, 1]] - vertices[faces[:, 0]]
+    v2 = vertices[faces[:, 2]] - vertices[faces[:, 0]]
+    triangle_normals = np.cross(v1, v2)
+
+    # Normalize the normal vectors to get their length (i.e., triangle area)
+    triangle_areas = np.linalg.norm(triangle_normals, axis=1) / 2
+
+    # Sum up the areas to get the total area of the mesh
+    mesh_area = np.sum(triangle_areas)
+
+    return mesh_area
+
+
+def get_area(geometry):
+    verts = geometry.verts
+    faces = geometry.faces
+    vertices = np.array([[verts[i], verts[i + 1], verts[i + 2]] for i in range(0, len(verts), 3)])
+    faces = np.array([[faces[i], faces[i + 1], faces[i + 2]] for i in range(0, len(faces), 3)])
+    return get_area_vf(vertices, faces)
+
+
+def get_side_area(geometry):
+    verts = geometry.verts
+    faces = geometry.faces
+    vertices = np.array([[verts[i], verts[i + 1], verts[i + 2]] for i in range(0, len(verts), 3)])
+    faces = np.array([[faces[i], faces[i + 1], faces[i + 2]] for i in range(0, len(faces), 3)])
+
+    # Calculate the triangle normal vectors
+    v1 = vertices[faces[:, 1]] - vertices[faces[:, 0]]
+    v2 = vertices[faces[:, 2]] - vertices[faces[:, 0]]
+    triangle_normals = np.cross(v1, v2)
+
+    # Normalize the normal vectors
+    triangle_normals = triangle_normals / np.linalg.norm(triangle_normals, axis=1)[:, np.newaxis]
+
+    # Find the faces with a normal vector pointing in the desired +Y normal direction
+    filtered_face_indices = np.where(triangle_normals[:, 1] > tol)[0]
+    filtered_faces = faces[filtered_face_indices]
+    return get_area_vf(vertices, filtered_faces)
+
+
+def get_footprint_area(geometry):
+    verts = geometry.verts
+    faces = geometry.faces
+    vertices = np.array([[verts[i], verts[i + 1], verts[i + 2]] for i in range(0, len(verts), 3)])
+    faces = np.array([[faces[i], faces[i + 1], faces[i + 2]] for i in range(0, len(faces), 3)])
+
+    # Calculate the triangle normal vectors
+    v1 = vertices[faces[:, 1]] - vertices[faces[:, 0]]
+    v2 = vertices[faces[:, 2]] - vertices[faces[:, 0]]
+    triangle_normals = np.cross(v1, v2)
+
+    # Normalize the normal vectors
+    triangle_normals = triangle_normals / np.linalg.norm(triangle_normals, axis=1)[:, np.newaxis]
+
+    # Find the faces with a normal vector pointing in the desired +Z normal direction
+    filtered_face_indices = np.where(triangle_normals[:, 2] > tol)[0]
+    filtered_faces = faces[filtered_face_indices]
+    return get_area_vf(vertices, filtered_faces)
+
+
+def get_outer_surface_area(geometry):
+    verts = geometry.verts
+    faces = geometry.faces
+    vertices = np.array([[verts[i], verts[i + 1], verts[i + 2]] for i in range(0, len(verts), 3)])
+    faces = np.array([[faces[i], faces[i + 1], faces[i + 2]] for i in range(0, len(faces), 3)])
+
+    # Calculate the triangle normal vectors
+    v1 = vertices[faces[:, 1]] - vertices[faces[:, 0]]
+    v2 = vertices[faces[:, 2]] - vertices[faces[:, 0]]
+    triangle_normals = np.cross(v1, v2)
+
+    # Normalize the normal vectors
+    triangle_normals = triangle_normals / np.linalg.norm(triangle_normals, axis=1)[:, np.newaxis]
+
+    # Find the faces with a normal vector that isn't +Z or -Z
+    filtered_face_indices = np.where(abs(triangle_normals[:, 2]) < tol)[0]
+    filtered_faces = faces[filtered_face_indices]
+    return get_area_vf(vertices, filtered_faces)
+
+
+def get_footprint_perimeter(geometry):
+    verts = geometry.verts
+    faces = geometry.faces
+    vertices = np.array([[verts[i], verts[i + 1], verts[i + 2]] for i in range(0, len(verts), 3)])
+    faces = np.array([[faces[i], faces[i + 1], faces[i + 2]] for i in range(0, len(faces), 3)])
+
+    # Calculate the triangle normal vectors
+    v1 = vertices[faces[:, 1]] - vertices[faces[:, 0]]
+    v2 = vertices[faces[:, 2]] - vertices[faces[:, 0]]
+    triangle_normals = np.cross(v1, v2)
+
+    # Normalize the normal vectors
+    triangle_normals = triangle_normals / np.linalg.norm(triangle_normals, axis=1)[:, np.newaxis]
+
+    # Find the faces with a normal vector pointing in the negative Z direction
+    negative_z_face_indices = np.where(triangle_normals[:, 2] < -tol)[0]
+    negative_z_faces = faces[negative_z_face_indices]
+
+    # Initialize the set of counted edges and the perimeter
+    all_edges = set()
+    shared_edges = set()
+    perimeter = 0
+
+    # Loop through each face
+    for face in negative_z_faces:
+        # Loop through each edge of the face
+        for i in range(3):
+            # Get the indices of the two vertices that define the edge
+            edge = (face[i], face[(i + 1) % 3])
+            # Keep track of shared edges. Perimeter edges are unshared.
+            if (edge[1], edge[0]) in all_edges or (edge[0], edge[1]) in all_edges:
+                shared_edges.add((edge[0], edge[1]))
+                shared_edges.add((edge[1], edge[0]))
+            else:
+                all_edges.add(edge)
+
+    return sum([np.linalg.norm(vertices[e[0]] - vertices[e[1]]) for e in (all_edges - shared_edges)])