Blender script - export mesh to vertex/index buffers (for Rust)

io_buffers.py

from collections import namedtuple
from itertools import zip_longest
import bpy

# Copied from https://docs.python.org/3/library/itertools.html#itertools-recipes
# Used for grouping triangle vertex indices
def grouper(iterable, n, *, incomplete='fill', fillvalue=None):
    "Collect data into non-overlapping fixed-length chunks or blocks"
    # grouper('ABCDEFG', 3, fillvalue='x') --> ABC DEF Gxx
    # grouper('ABCDEFG', 3, incomplete='strict') --> ABC DEF ValueError
    # grouper('ABCDEFG', 3, incomplete='ignore') --> ABC DEF
    args = [iter(iterable)] * n
    if incomplete == 'fill':
        return zip_longest(*args, fillvalue=fillvalue)
    if incomplete == 'strict':
        return zip(*args, strict=True)
    if incomplete == 'ignore':
        return zip(*args)
    else:
        raise ValueError('Expected fill, strict, or ignore')

output_vertices = "pub const VERTICES: [Vertex; {count}] = [\n{vertices}\n];"
output_indices = "pub const INDICES: [u32; {count}] = [\n{indices}\n];"

output_vertex = """Vertex {{
    position: Vec3 {{ x: {position.x:.4f}, y: {position.y:.4f}, z: {position.z:.4f} }},
    tex_coords: Vec2 {{ x: {tex_coords.x:.4f}, y: {tex_coords.y:.4f} }},
}}"""

ob = bpy.context.active_object
obm = ob.to_mesh()
obm.transform(ob.matrix_world)
obm.calc_loop_triangles()

BufferVertex = namedtuple("BufferVertex", "position tex_coords")
looped_vertices = {}
indices = []
for loopt in obm.loop_triangles:
    for loop in loopt.loops:
        loop = obm.loops[loop]
        pos = obm.vertices[loop.vertex_index].co.copy().freeze()
        uv = obm.uv_layers.active.uv[loop.index].vector.copy()
        uv.y = 1 - uv.y
        uv.freeze()
        bv = BufferVertex(pos, uv)
        looped_index = looped_vertices.setdefault(bv, len(looped_vertices))
        indices.append(looped_index)
vertices = sorted(looped_vertices.keys(), key=looped_vertices.get)

with open("/tmp/data", "w") as dataf:
    dataf.write("// The following data was auto-generated "
                "by Blender " + bpy.app.version_string + "\n\n")
    dataf.write(
        output_vertices.format(
            count=len(vertices),
            vertices=",\n".join(map(\
                lambda v: output_vertex.format(**v._asdict()), \
                vertices))
        )
    )
    dataf.write("\n\n// ============================\n\n")
    dataf.write(
        output_indices.format(
            count=len(indices),
            indices=",\n".join(\
                map(", ".join, \
                    grouper(map(str, indices), 3, incomplete="strict"))
            )
        )
    )

ob.to_mesh_clear()