Removing export from python binding

[elalish]

Fixes #128

I found a nice little python library for import/export of various mesh formats: meshio. By removing this last dependency, we can separate our library completely from Assimp. However, this isn't yet functional because it seems the to_mesh function isn't working. I get the following Python error when I try python3 run_all.py -e:

TypeError: Unregistered type : glm::vec<3, int, (glm::qualifier)0>

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "run_all.py", line 38, in <module>
    cells = [("triangle", mesh.tri_verts)]
TypeError: Unable to convert function return value to a Python type! The signature was
	(self: pymanifold.Mesh) -> List[glm::vec<3, int, (glm::qualifier)0>]

I think we need to convert our std::vector<glm::vec3> into a two-dimensional python list, but I'm not sure how to do that. Any thoughts @pca006132?

UPDATE: working now.

[codecov-commenter]

Codecov Report

Merging #190 (656c0b7) into master (405dd63) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #190   +/-   ##
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  Coverage   98.66%   98.66%           
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  Files          32       32           
  Lines        2913     2913           
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  Hits         2874     2874           
  Misses         39       39           

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[pca006132]

We can use numpy array. https://pybind11.readthedocs.io/en/stable/advanced/pycpp/numpy.html

More specifically, it should be something similar to

manifold/bindings/python/pymanifold.cpp

Lines 188 to 218 in 11e58ea

	.def(py::init([](py::array_t<float> &vertPos, py::array_t<int> &triVerts,
	py::array_t<float> &vertNormal,
	py::array_t<float> &halfedgeTangent) {
	auto vertPos_view = vertPos.unchecked<2>();
	auto triVerts_view = triVerts.unchecked<2>();
	auto vertNormal_view = vertNormal.unchecked<2>();
	auto halfedgeTangent_view = halfedgeTangent.unchecked<2>();
	if (vertPos_view.shape(1) != 3)
	throw std::runtime_error("Invalid vert_pos shape");
	if (triVerts_view.shape(1) != 3)
	throw std::runtime_error("Invalid tri_verts shape");
	if (vertNormal_view.shape(0) != 0) {
	if (vertNormal_view.shape(1) != 3)
	throw std::runtime_error("Invalid vert_normal shape");
	if (vertNormal_view.shape(0) != vertPos_view.shape(0))
	throw std::runtime_error(
	"vert_normal must have the same length as vert_pos");
	}
	if (halfedgeTangent_view.shape(0) != 0) {
	if (halfedgeTangent_view.shape(1) != 4)
	throw std::runtime_error("Invalid halfedge_tangent shape");
	if (halfedgeTangent_view.shape(0) != triVerts_view.shape(0) * 3)
	throw std::runtime_error(
	"halfedge_tangent must be three times as long as "
	"tri_verts");
	}
	std::vector<glm::vec3> vertPos_vec(vertPos_view.shape(0));
	std::vector<glm::ivec3> triVerts_vec(triVerts_view.shape(0));
	std::vector<glm::vec3> vertNormal_vec(vertNormal_view.shape(0));
	std::vector<glm::vec4> halfedgeTangent_vec(
	halfedgeTangent_view.shape(0));

but we should flatten the buffer instead.

[elalish]

@pca006132 Thanks, I think I've got all the python stuff working now, following your suggestion. I tried to install the python meshio package for nix (they seem to have it), but I think I'm just not familiar enough with the syntax. Would you mind giving it a look?

[pca006132]

Try this:

python39.withPackages(ps: with ps; [meshio])

it seems that they don't have it for 3.8.

[elalish]

Perfect, thanks!

[elalish]

@rsaccon This improved our python bindings considerably, which should make it a lot easier to integrate with Blender. Are you still interested in giving that a go? Would love to see that connection made.