Wrapping Mesh fields in Option<T>

[EtaLoop]

Wrapping Mesh fields (vertices, normals, texcoords, faces, colors) in Option would be easier to check.
For example, checking if mesh.normals is Some is more convenient that checking if normals.is_empty() && normals[0].is_empty().

[taiki-e]

I don't have a strong opinion on this, but if we do this, we need to figure out which ones are Optional in the spec and which ones should actually be treated as Optional.

For example, why do you want vertices and faces to be Optional as well?
(Btw, our examples do not treat them as options.)

mesh-loader/examples/kiss3d/src/main.rs

Lines 118 to 136 in 8754042

	let coords = mesh.vertices.into_iter().map(Into::into).collect();
	let faces = mesh
	.faces
	.into_iter()
	.map(|f| na::Point3::new(f[0], f[1], f[2]))
	.collect();
	let normals = if mesh.normals.is_empty() {
	None
	} else {
	Some(mesh.normals.into_iter().map(Into::into).collect())
	};
	let uvs = if mesh.texcoords[0].is_empty() {
	None
	} else {
	Some(mesh.texcoords[0].iter().copied().map(Into::into).collect())
	};
	let kiss3d_mesh = Rc::new(RefCell::new(kiss3d::resource::Mesh::new(
	coords, faces, normals, uvs, false,
	)));

mesh-loader/examples/bevy/src/main.rs

Lines 226 to 258 in 8550526

	bevy_mesh.insert_attribute(Mesh::ATTRIBUTE_POSITION, positions);
	if mesh.texcoords[0].is_empty() {
	let uvs = vec![[0.0, 0.0]; num_vertices];
	bevy_mesh.insert_attribute(Mesh::ATTRIBUTE_UV_0, uvs);
	} else {
	bevy_mesh.insert_attribute(Mesh::ATTRIBUTE_UV_0, mem::take(&mut mesh.texcoords[0]));
	}
	if !mesh.colors[0].is_empty() {
	let colors: Vec<[f32; 4]> = mesh.colors[0]
	.iter()
	.map(|c| {
	// TODO
	Color::Rgba {
	red: c[0],
	green: c[1],
	blue: c[2],
	alpha: c[3],
	}
	.as_linear_rgba_f32()
	})
	.collect();
	bevy_mesh.insert_attribute(Mesh::ATTRIBUTE_COLOR, colors);
	}
	bevy_mesh.set_indices(Some(Indices::U32(indices)));
	if mesh.normals.is_empty() {
	bevy_mesh.duplicate_vertices();
	bevy_mesh.compute_flat_normals();
	} else {
	bevy_mesh.insert_attribute(
	Mesh::ATTRIBUTE_NORMAL,
	VertexAttributeValues::Float32x3(mesh.normals),
	);
	}

[EtaLoop]

You are right, vertices shouldn't be optional, it was my mistake.
I don't really know what are faces btw.. It is something you're making by yourself or is it given in the collada file?