Handle mesh with multiple <triangles> that having material

[EtaLoop]

In this collada 1.4.1 file, there are multiple <triangles> described. Please correct me if I'm wrong, but the parser does not seem to handle it.
Multiple <triangles> involve vertex positions, normals but also multiple materials.

EDIT : I assume, using multiple <triangles> aims at having different materials/color for a mesh. So, maybe we could use some kind of vertex_color which would be a list of color for each vertex? It would permit to describe both materials.

https://github.com/Gepetto/example-robot-data/blob/master/robots/ur_description/meshes/ur3/visual/base.dae

[taiki-e]

Thanks for the report!

The multiple primitives themselves are parsed fine, and all are taken into account when building the mesh. However, when building the material, only the first one specified is taken into account. We need to figure out some way to represent this well...

mesh-loader/src/collada/geometry.rs

Lines 232 to 235 in 8754042

	"lines" | "linestrips" | "polygons" | "polylist" | "triangles" | "trifans"
	| "tristrips" => {
	primitives.push(parse_primitive(node, name.parse().unwrap())?);
	}

mesh-loader/src/collada/instance.rs

Line 113 in e114889

for prim in (iter::Mesh { doc, xml: geometry }).primitives() {

mesh-loader/src/collada/instance.rs

Lines 87 to 93 in e114889

	for mat in geometry.mesh.primitives.iter().filter_map(|m| m.material) {
	if let Some(&(name, effect)) = instance_material_map.get(mat) {
	material = Some(build_material(doc, name, effect, dir));
	// TODO: multiple materials from geometry.mesh.primitives?
	break;
	}
	}