Fix bug in cylinder_from_points (for real this time)

openmc/model/funcs.py

@@ -409,10 +409,10 @@ def cylinder_from_points(p1, p2, r, **kwargs):
     kwargs['d'] = -2*dx*dy
     kwargs['e'] = -2*dy*dz
     kwargs['f'] = -2*dx*dz
-    kwargs['g'] = cy*dz - cz*dy
-    kwargs['h'] = cz*dx - cx*dz
-    kwargs['j'] = cx*dy - cy*dx
-    kwargs['k'] = -(dx*dx + dy*dy + dz*dz)*r*r
+    kwargs['g'] = 2*(cy*dz - cz*dy)
+    kwargs['h'] = 2*(cz*dx - cx*dz)
+    kwargs['j'] = 2*(cx*dy - cy*dx)
+    kwargs['k'] = cx*cx + cy*cy + cz*cz - (dx*dx + dy*dy + dz*dz)*r*r
 
     return openmc.Quadric(**kwargs)
 

tests/unit_tests/test_surface.py

@@ -362,3 +362,31 @@ def test_cylinder_from_points():
         assert p2 + 1.1*r*n in +s
         assert p1 + 0.9*r*n in -s
         assert p2 + 0.9*r*n in -s
+
+
+def test_cylinder_from_points_axis():
+    # Create axis-aligned cylinders and confirm the coefficients are as expected
+
+    # (x - 3)^2 + (y - 4)^2 = 2^2
+    # x^2 + y^2 - 6x - 8y + 21 = 0
+    s = openmc.model.cylinder_from_points((3., 4., 0.), (3., 4., 1.), 2.)
+    assert (s.a, s.b, s.c) == pytest.approx((1., 1., 0.))
+    assert (s.d, s.e, s.f) == pytest.approx((0., 0., 0.))
+    assert (s.g, s.h, s.j) == pytest.approx((-6., -8., 0.))
+    assert s.k == pytest.approx(21.)
+
+    # (y + 7)^2 + (z - 1)^2 = 3^2
+    # y^2 + z^2 + 14y - 2z + 41 = 0
+    s = openmc.model.cylinder_from_points((0., -7, 1.), (1., -7., 1.), 3.)
+    assert (s.a, s.b, s.c) == pytest.approx((0., 1., 1.))
+    assert (s.d, s.e, s.f) == pytest.approx((0., 0., 0.))
+    assert (s.g, s.h, s.j) == pytest.approx((0., 14., -2.))
+    assert s.k == 41.
+
+    # (x - 2)^2 + (z - 5)^2 = 4^2
+    # x^2 + z^2 - 4x - 10z + 13 = 0
+    s = openmc.model.cylinder_from_points((2., 0., 5.), (2., 1., 5.), 4.)
+    assert (s.a, s.b, s.c) == pytest.approx((1., 0., 1.))
+    assert (s.d, s.e, s.f) == pytest.approx((0., 0., 0.))
+    assert (s.g, s.h, s.j) == pytest.approx((-4., 0., -10.))
+    assert s.k == pytest.approx(13.)