Add an example of constitutive solid geometry

examples/boolean.py

@@ -0,0 +1,57 @@
+"""Boolean operations on a sphere, a box and two cylinders."""
+
+# This reimplements gmsh/examples/boolean/boolean.geo in Python.
+from __future__ import annotations
+
+import sys
+
+import gmsh
+import pyvista as pv
+
+R = 1.4
+Rs = R * 0.7
+Rt = R * 1.25
+
+# %%
+# Behavior due to flipped normals
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+# Note that these boolean filters behave differently depending on the
+# orientation of the normals.
+#
+# Boolean difference with both cube and sphere normals pointed
+# outward.  This is the "normal" behavior.
+
+cube = pv.Cube().triangulate().subdivide(3)
+sphere = pv.Sphere(radius=0.6)
+result = cube.boolean_difference(sphere)
+result.plot(show_edges=True, color="white")
+
+gmsh.initialize(sys.argv)
+
+gmsh.model.add("boolean")
+
+# from http://en.wikipedia.org/wiki/Constructive_solid_geometry
+
+gmsh.option.setNumber("Mesh.Algorithm", 6)
+gmsh.option.setNumber("Mesh.MeshSizeMin", 0.4)
+gmsh.option.setNumber("Mesh.MeshSizeMax", 0.4)
+
+gmsh.model.occ.addBox(-R, -R, -R, 2 * R, 2 * R, 2 * R, 1)
+gmsh.model.occ.addSphere(0, 0, 0, Rt, 2)
+gmsh.model.occ.intersect([(3, 1)], [(3, 2)], 3)
+gmsh.model.occ.addCylinder(-2 * R, 0, 0, 4 * R, 0, 0, Rs, 4)
+gmsh.model.occ.addCylinder(0, -2 * R, 0, 0, 4 * R, 0, Rs, 5)
+gmsh.model.occ.addCylinder(0, 0, -2 * R, 0, 0, 4 * R, Rs, 6)
+gmsh.model.occ.fuse([(3, 4), (3, 5)], [(3, 6)], 7)
+gmsh.model.occ.cut([(3, 3)], [(3, 7)], 8)
+
+gmsh.model.occ.synchronize()
+
+gmsh.model.mesh.generate(3)
+
+gmsh.write("boolean.msh")
+
+gmsh.finalize()
+
+mesh = pv.read("boolean.msh")
+mesh.plot(show_edges=True, color="white")