Intersection between watertight mesh and plane mesh

[omaralvarez]

I am using cut_with_mesh to obtain the part of a plane mesh that is inside another mesh. What I am using now:

mesh = trimesh2vedo(plane_mesh).cut_with_mesh(trimesh2vedo(mesh))

It looks like this:

Right now it is crashing silently and I do not know why. I am using the right function to do this?

[omaralvarez]

I have also tested cut_with_box and it does not work either. Could it be due to the mesh not interseting in all sides with the bounding box (mesh just intersects with one side)?

[marcomusy]

It could be! but I cannot tell, you are not giving me enough information.. :) Syntax looks ok though.

[omaralvarez]

Sorry, you are right, I have made a drawing to make it clearer:

I have the mesh of a plane, and I want to get the area of the part that is inside the box in the drawing (A). plane_mesh is the plane, and mesh is the mesh of the box. I have tested both meshes inside vedo, and the render looks ok. I have also tested cut_with_box with mesh coverted to a vedo Box.

The cut always is empty, not sure why.

I hope that now it is clearer, sorry for the drawing skills.

[marcomusy]

No worries! This seems to work though

from vedo import Cube, Plane, show, settings

settings.use_parallel_projection = True

cube = Cube().rotate_z(10).alpha(0.5)
plane = Plane().scale(0.5).rotate_x(5).shift(dx=0.6)
# cube.subdivide(3, method=1)
# plane.subdivide(3, method=1)

cut_plane = plane.clone().cut_with_mesh(cube).shift(dz=0.01)
cut_plane.c("red5")

show(cube, plane, cut_plane, axes=1)

Note that this doesn´t work if some edges are exactly coincident as then the inside/outside becomes ambiguous.

[omaralvarez]

That may be the problem, the front and back edges are common. The rest should not match. Here is the full code of one of the failing cases:

from vedo import Cube, Mesh, show

box = Box(pos=[0.00073, 0.00279, 0.03353, 0.03529, 0.0, 0.07])

face_mesh = Mesh(
    [[0.00041, 0.035, 0.0],[0.00104, 0.03498, 0.0], [0.00104, 0.03498, 0.07]], 
    [[2, 1, 0]]
)

cut = face_mesh.clone().cut_with_box(box)
cut.c("red5")

show(box, face_mesh, cut)

It's weird because when it is fully inside it works:

[marcomusy]

that might be a problem of precision (?)

from vedo import *

box = Box(pos=[0.00073, 0.00279, 0.03353, 0.03529, 0.0, 0.07])

face_mesh = Mesh(
    [[
     [0.00041, 0.035, 0.0],
     [0.00104, 0.03498, 0.0], 
     [0.00104, 0.03498, 0.07]
     ], 
    [[2, 1, 0]]]
)

face_mesh.subdivide(3, method=1)
box.subdivide(3, method=1)
box.alpha(0.5).lighting('off')

cut = face_mesh.clone().cut_with_box(box)
cut.c("red5")

show(box, cut)

[omaralvarez]

You are right. Let me investigate further with your suggested code. Thanks for the help I'll let you know what I find out!

[omaralvarez]

It looks like indeed it was a matter of precision. Subdividing the meshes results look correct. Thank you very much for the help.