Applying certains transforms when creating a mesh based on revolve ends with is_volume == False

[spichardo]

Hi

I found this weird error when updating to the latest version of trimesh (4.7.3). I spotted this issue when trying to do some boolean operations and trimesh complained one of the meshes was not a volume.

If you create a simple cone mesh with a transform to flip the object in any of the directions (i.e. Z), it ends with is_volume == False

Transform=np.eye(4)
Transform[2,2]=-1
cone=trimesh.creation.cone(20,10,transform=Transform)
print('Cone is a volume =',cone.is_volume)

Cone is a volume = False

But if you apply the transformation after creating the object, it remains valid as a volume

cone=trimesh.creation.cone(20,10)
cone.apply_transform(Transform)
print('Cone is a volume =',cone.is_volume)

Cone is a volume = True

The documentation is clear that the transformation is applied after creation if passed when creating the object, but somehow this is not done exactly as if done in user code.

The error also shows when creating a cylinder, but not with a non-revolve-based mesh, such as a box.

box=trimesh.creation.box([5,10,20],transform=Transform)
print('Box is a volume =',box.is_volume)

Box is a volume = True

This bug seems independent of numpy version (tested it 1.24.3 and 2.0.2)

Cheers,

Sam