make sure subdivisions=0 still refines radius

tests/test_primitives.py

@@ -343,6 +343,16 @@ def test_sphere_subdivisions(self):
 
         assert a.faces.shape == b.faces.shape
 
+    def test_sphere_subdivisions_radius(self):
+        tf = list(g.random_transforms(4))
+        for r in [1e-4, 1.1, 3, 1213.22]:
+            for subd in range(4):
+                s = g.trimesh.primitives.Sphere(
+                    radius=r, transform=tf[subd], subdivisions=subd
+                )
+                rc = g.np.linalg.norm(s.vertices - s.center_mass, axis=1)
+                assert g.np.isclose(rc.mean(), r)
+
 
 if __name__ == "__main__":
     g.trimesh.util.attach_to_log()

trimesh/creation.py

@@ -855,16 +855,26 @@ def icosphere(subdivisions: Integer = 3, radius: Number = 1.0, **kwargs):
     ico : trimesh.Trimesh
       Meshed sphere
     """
+    radius = float(radius)
+    subdivisions = int(subdivisions)
 
     ico = icosahedron()
     ico._validate = False
+
     for _ in range(subdivisions):
         ico = ico.subdivide()
         vectors = ico.vertices
         scalar = np.sqrt(np.dot(vectors**2, [1, 1, 1]))
         unit = vectors / scalar.reshape((-1, 1))
         ico.vertices += unit * (radius - scalar).reshape((-1, 1))
 
+    # if we didn't subdivide we still need to refine the radius
+    if subdivisions <= 0:
+        vectors = ico.vertices
+        scalar = np.sqrt(np.dot(vectors**2, [1, 1, 1]))
+        unit = vectors / scalar.reshape((-1, 1))
+        ico.vertices += unit * (radius - scalar).reshape((-1, 1))
+
     if "color" in kwargs:
         warnings.warn(
             "`icosphere(color=...)` is deprecated and will "