How to create Triangle UV map for Custom Mesh

Using custom mesh, I’ve created tesselated octahedron and now want to map texture onto triangles(like on screenshot), but info on MakeCanvasUVTri seems to be quite sparse. So, are there any other methods to create UV map for custom mesh or to highlight edges?

usually you would just uv unwrap the mesh in a third party program such as blender or maya. this allows you to place the uv as you choose and in the shape that you like. the picture you posted even looks like its from blender.