BunnyLOD VS Bplus.jl

If you reuse the same index buffer as proposed then you won't be able to share vertices, which can be an important optimization. In my case I use a 323 cache of vert indices and just insert an index rather than a vertex if the vertex already exists and has the same material. I generate normals in the pixel shader to increase what can be shared, and then use a variant of Stan Melax's edge collapse polygon reduction algorithm to combine edges and reduce triangle count.

You might want to take a look at Stan Melax's easy mesh simplification technique with edge collapse at http://www.melax.com/polychop (read the full article link) - I've ported the code so it runs cross platform on https://github.com/dougbinks/BunnyLOD

I use a variant of progressive meshing, but constrained to preserve edges, normals and ambient occulusion in Avoyd based on Stan Melax's work: https://github.com/dougbinks/BunnyLOD

My triangle reduction in Avoyd, loosely based on Stan Melax's progressive mesh approach checks that the vertex being removed is internal to a set of triangles by checking that the internal angles add up to roughly 2Pi. This also ensures only flat surfaces are reduced, although I also perform normal checks and that vertex ambient occlusion gradients are preserved.