New get_shape_matrix utility.

src/ifcopenshell-python/docs/ifcopenshell-python/geometry_processing.rst

@@ -20,6 +20,7 @@ related information in ``shape.geometry``:
 
     import ifcopenshell
     import ifcopenshell.geom
+    import ifcopenshell.util.shape
 
     ifc_file = ifcopenshell.open('model.ifc')
     element = ifc_file.by_type('IfcWall')[0]
@@ -55,19 +56,25 @@ related information in ``shape.geometry``:
     # Objects are never scaled, so the scale factor of the matrix is always 1.
     matrix = shape.transformation.matrix.data
 
-    # Indices of vertices per triangle face e.g. [f1v1, f1v2, f1v3, f2v1, f2v2, f2v3, ...]
-    faces = shape.geometry.faces
-
-    # Indices of vertices per edge e.g. [e1v1, e1v2, e2v1, e2v2, ...]
-    edges = shape.geometry.edges
+    # For convenience, you might want the matrix as a nested numpy array, so you can do matrix math.
+    matrix = ifcopenshell.util.shape.get_shape_matrix(shape)
 
     # X Y Z of vertices in flattened list e.g. [v1x, v1y, v1z, v2x, v2y, v2z, ...]
     verts = shape.geometry.verts
 
+    # Indices of vertices per edge e.g. [e1v1, e1v2, e2v1, e2v2, ...]
+    edges = shape.geometry.edges
+
+    # Indices of vertices per triangle face e.g. [f1v1, f1v2, f1v3, f2v1, f2v2, f2v3, ...]
+    faces = shape.geometry.faces
+
     # Since the lists are flattened, you may prefer to group them like so depending on your geometry kernel
-    grouped_verts = [[verts[i], verts[i + 1], verts[i + 2]] for i in range(0, len(verts), 3)]
-    grouped_edges = [[edges[i], edges[i + 1]] for i in range(0, len(edges), 2)]
-    grouped_faces = [[faces[i], faces[i + 1], faces[i + 2]] for i in range(0, len(faces), 3)]
+    # A nested numpy array e.g. [[v1x, v1y, v1z], [v2x, v2y, v2z], ...]
+    grouped_verts = ifcopenshell.util.shape.get_vertices(shape.geometry)
+    # A nested numpy array e.g. [[e1v1, e1v2], [e2v1, e2v2], ...]
+    grouped_edges = ifcopenshell.util.shape.get_edges(shape.geometry)
+    # A nested numpy array e.g. [[f1v1, f1v2, f1v3], [f2v1, f2v2, f2v3], ...]
+    grouped_faces = ifcopenshell.util.shape.get_faces(shape.geometry)
 
     # A list of styles that are relevant to this shape
     styles = shape.geometry.materials

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

@@ -66,6 +66,11 @@ def get_z(geometry):
     return max(z_values) - min(z_values)
 
 
+def get_shape_matrix(shape):
+    m = shape.transformation.matrix.data
+    return np.array(([m[0], m[3], m[6], m[9]], [m[1], m[4], m[7], m[10]], [m[2], m[5], m[8], m[11]], [0, 0, 0, 1]))
+
+
 def get_bbox_centroid(geometry):
     x_values = [geometry.verts[i] for i in range(0, len(geometry.verts), 3)]
     y_values = [geometry.verts[i + 1] for i in range(0, len(geometry.verts), 3)]
@@ -89,9 +94,7 @@ def get_element_bbox_centroid(element, geometry):
 
 def get_shape_bbox_centroid(shape, geometry):
     centroid = get_bbox_centroid(geometry)
-    m = shape.transformation.matrix.data
-    mat = np.array(([m[0], m[3], m[6], m[9]], [m[1], m[4], m[7], m[10]], [m[2], m[5], m[8], m[11]], [0, 0, 0, 1]))
-    return (mat @ np.array([*centroid, 1.0]))[0:3]
+    return (get_shape_matrix(shape) @ np.array([*centroid, 1.0]))[0:3]
 
 
 def get_vertices(geometry):
@@ -110,14 +113,15 @@ def get_faces(geometry):
 
 
 def get_shape_vertices(shape, geometry):
-    m = shape.transformation.matrix.data
-    mat = np.array(([m[0], m[3], m[6], m[9]], [m[1], m[4], m[7], m[10]], [m[2], m[5], m[8], m[11]], [0, 0, 0, 1]))
+    verts = get_vertices(geometry)
+    mat = get_shape_matrix(shape)
     return np.array([mat @ np.array([verts[i], verts[i + 1], verts[i + 2]]) for i in range(0, len(verts), 3)])
 
 
 def get_element_vertices(element, geometry):
+    verts = get_vertices(geometry)
     if not element.ObjectPlacement or not element.ObjectPlacement.is_a("IfcLocalPlacement"):
-        return get_shape_vertices(geometry)
+        return verts
     mat = ifcopenshell.util.placement.get_local_placement(element.ObjectPlacement)
     return np.array([mat @ np.array([verts[i], verts[i + 1], verts[i + 2]]) for i in range(0, len(verts), 3)])