CODEWITHSUNDEEP
python3dgeometrymeshtrimesh
Jared Boyer
Jared Boyer

Reputation: 21

How to calculate the volumetric intersection of two meshes using Trimesh?

I'm trying to calculate the volume of the intersection of two convex meshes using Trimesh. Using the trimesh.Trimesh.intersection() method, even basic, clearly overlapping shapes are returning with an empty intersection.

As a simple example, I tried calculating the intersection of two boxes offset from one another.

# Create offset transformation matrix
T = np.eye(4)
T[:3, 3] = np.array([0.5, 0.5, 0.5])

# Form basic box meshes
mesh1 = trimesh.creation.box(extents=[1.0, 1.0, 1.0])
mesh2 = trimesh.creation.box(extents=[1.0, 1.0, 1.0], transform=T)

# Calculate intersection
test_intersection = mesh1.intersection(mesh2)

print(test_intersection)
print(test_intersection.volume)

# Visualize
scene = trimesh.Scene([mesh1, mesh2])
scene.show()

The resulting outputs indicate an empty intersection between the two shapes:

<trimesh.Trimesh(vertices.shape=(0, 3), faces.shape=(0, 3))>
0.0

Yet visualizing the boxes, they are clearly overlapping:

boxes

Why is the mesh intersection empty? Am I misunderstanding the use of the .intersection() method?

(I'm using python 3.12.7, trimesh 4.5.2 installed from pip)

Upvotes: 1

Views: 258

Answers (1)

Jared Boyer
Jared Boyer

Reputation: 21

I solved my issue by installing the additional dependency

pip install manifold3d

Which I tried after looking through the source code for the trimesh.Trimesh.intersection method and seeing the following docstring:

Parameters
     ------------
     other : trimesh.Trimesh, or list of trimesh.Trimesh objects
       Meshes to calculate intersections with
     engine
       Which backend to use, the default
       recommendation is: `pip install manifold3d`.

Without this dependency, calling the intersection method on a trimesh object returns an empty mesh rather than indicating the missing engine / dependency

Upvotes: 1

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