Option for Interleaved Vertex Attributes

Having interleaved vertex attributes is supported by glTF format. However, the exported doesn’t expose interleaving of attributes; it would be more performant to have attributes intersparsed. It’d be great to get an option to enable it if needed.

This would mean

• Making the interleaved array
• Giving the right byteStride for each attribute

[donmccurdy]

There are some indirect benefits of interleaved vertex attributes, like minimizing the total number of WebGL buffers used for the scene (see this thread). But I don’t have real numbers on this, and would be very interested in a real comparison on modern graphics APIs.

But I think I’m inclined to agree that this is out of the scope that Blender’s exporter should need to deal with, and should be left to tools focused on glTF optimization (e.g. glTF-Pipeline, gltfpack, glTF-Transform, RapidCompact, …). Correct import/export in Blender is a big enough project.

[hrydgard]

Your original link is from 2013. Since then GPUs have gained more general caching systems that work more like on CPU, and with that, it’s pretty obvious that if you sometimes need to access one of the vertex streams separately, as with Z-prepass or shadow map rendering where you only use position, it’ll be better to have them separate, otherwise when doing so the GPU will load lots of irrelevant data into the cache.

Depending on attribute usage patterns, the optimum can even be to have positions separate and everything else interleaved, but the wins either way are very small.

This is all kind of received knowledge in the graphics community, not so easy to find good references, but there’s this from 2016:

https://anteru.net/blog/2016/storing-vertex-data-to-interleave-or-not-to-interleave/

ARM actually recommends mixed deinterleave: https://developer.arm.com/solutions/graphics-and-gaming/developer-guides/learn-the-basics/the-bifrost-shader-core/index-driven-geometry-pipeline

Anyway, again, it’s generally not what’s gonna be your bottleneck these days.