Objective

It can sometimes be useful to combine several meshes into one. This allows constructing more complex meshes out of simple primitives without needing to use a 3D modeling program or entity hierarchies.

This could also be used internally to increase code reuse by using existing mesh generation logic for e.g. circles and using that in cylinder mesh generation logic to add the top and bottom of the cylinder.

Note: This is not implementing CSGs (Constructive Solid Geometry) or any boolean operations, as that is much more complex. This is simply adding the mesh data of another mesh to a mesh.

Solution

Add a merge method to Mesh. It appends the vertex attributes and indices of other to self, resulting in a Mesh that is the combination of the two.

For example, you could do this:

let mut cuboid = Mesh::from(shape::Box::default());
let mut cylinder = Mesh::from(shape::Cylinder::default());
let mut torus = Mesh::from(shape::Torus::default());

cuboid.merge(cylinder);
cuboid.merge(torus);

This would result in cuboid being a Mesh that also has the cylinder mesh and torus mesh. In this case, they would just be placed on top of each other, but by utilizing #11454 we can transform the cylinder and torus to get a result like this:

This is just a single entity and a single mesh.