An example fails

[pauljurczak]

I'm trying to run an example from https://trimsh.org/examples/ray.html. I'm using Python 3.7.3 on Raspberry Pi 4 with the newest RPi OS. This snippet:

import numpy as np
import trimesh

mesh = trimesh.creation.icosphere()
ray_origins = np.array([[0, 0, -3], [2, 2, -3]])
ray_directions = np.array([[0, 0, 1], [0, 0, 1]])

locations, index_ray, index_tri = mesh.ray.intersects_location(
        ray_origins=ray_origins,
        ray_directions=ray_directions)
print('The rays hit the mesh at coordinates:\n', locations)

produces:

Traceback (most recent call last):
  File "/home/pi/pick/old/test-trimesh.py", line 10, in <module>
    ray_directions=ray_directions)
  File "/home/pi/.local/lib/python3.7/site-packages/trimesh/ray/ray_triangle.py", line 107, in intersects_location
    **kwargs)
  File "/home/pi/.local/lib/python3.7/site-packages/trimesh/ray/ray_triangle.py", line 64, in intersects_id
    tree=self.mesh.triangles_tree,
  File "/home/pi/.local/lib/python3.7/site-packages/trimesh/caching.py", line 109, in get_cached
    value = function(*args, **kwargs)
  File "/home/pi/.local/lib/python3.7/site-packages/trimesh/base.py", line 823, in triangles_tree
    tree = triangles.bounds_tree(self.triangles)
  File "/home/pi/.local/lib/python3.7/site-packages/trimesh/triangles.py", line 344, in bounds_tree
    tree = util.bounds_tree(triangle_bounds)
  File "/home/pi/.local/lib/python3.7/site-packages/trimesh/util.py", line 1756, in bounds_tree
    import rtree
  File "/home/pi/.local/lib/python3.7/site-packages/rtree/__init__.py", line 9, in <module>
    from .index import Rtree, Index  # noqa
  File "/home/pi/.local/lib/python3.7/site-packages/rtree/index.py", line 6, in <module>
    from . import core
  File "/home/pi/.local/lib/python3.7/site-packages/rtree/core.py", line 77, in <module>
    rt.Error_GetLastErrorNum.restype = ctypes.c_int
  File "/usr/lib/python3.7/ctypes/__init__.py", line 369, in __getattr__
    func = self.__getitem__(name)
  File "/usr/lib/python3.7/ctypes/__init__.py", line 374, in __getitem__
    func = self._FuncPtr((name_or_ordinal, self))
AttributeError: /usr/bin/python3: undefined symbol: Error_GetLastErrorNum

What is wrong?

[pauljurczak]

I tried this example on Ubuntu 20.04, and it works just fine. I vaguely recall that one of the dependencies of trimesh could not be satisfied on 32-bit Raspberry Pi OS. Perhaps this is the source of this error.

[mikedh]

No worries, yeah this error is in rtree which is what trimesh's slow built-in ray checks (i.e. vs embree) use for broad-phase checking. It looks like this error is related to a) no rtree wheels bundling libspatialindex are built for ARM and b) no libspatialindex installed. If it exists on a Rasberry Pi you might try an apt-get install libspatialindex-dev.

[pauljurczak]

Installing libspatialindex-dev fixes the problem. Thank you.