This release contains many improvements to the meshoptimizer library and some gltfpack enhancements! Some highlights:

Vertex codec v1 (enabled via meshopt_encodeVertexVersion(1)) provides increased compression ratio, faster decompression speed, and customizable compression levels. Depending on input data, compressed data can be up to 5-10% smaller and decode up to 10% faster. Additionally, decoding has been further optimized for modern AArch64 CPUs, achieving 20% higher decoding speed on Apple Silicon for both versions (up to 30% overall improvements for v1).

Meshlet builder (meshopt_buildMeshlets) now generates fewer disconnected clusters, improving rasterization performance by up to 5% on certain meshes. Additionally, this algorithm now exposes extra options (via meshopt_buildMeshletsFlex) to create more axis-aligned clusters and further reduce disconnected clusters. This benefits use cases like clustered ray tracing (for Nvidia RTX) and hierarchical clusterization. For hierarchical clusterization, a new experimental algorithm, meshopt_partitionClusters, can be used to build the cluster hierarchy, and meshopt_computeSphereBounds can be used to compute the necessary bounds.

The majority of the work on the core library in this release has been sponsored by Valve; thank you!

Note: gltfpack development is done in spare time; potential corporate sponsors should feel free to reach out via e-mail.

Library improvements

• meshopt_encodeVertexVersion now supports version 1, which results in better compression ratio and faster decoding
• Default vertex codec version does not change in this version; applications that produce compressed data for glTF storage should call meshopt_encodeVertexVersion(0) to ensure that future library upgrades do not alter the encoding
• An experimental function, meshopt_encodeVertexBufferLevel, allows adjusting the compression level to balance between compression ratio and encoding speed (only available for version 1)
• meshopt_decodeVertexBuffer has been further optimized for some AArch64 systems, with up to 20% speedup on Apple Silicon
• meshopt_decodeVertexVersion/meshopt_decodeIndexVersion allow inspecting the encoded version of the compressed buffer
• meshopt_simplifyWithAttributes uses a more careful evaluation of attribute error on attribute seams, improving attribute quality
• meshopt_buildMeshlets now produces significantly fewer disconnected clusters, resulting in ~5% rasterization performance improvement in some cases
• meshopt_buildMeshlets is significantly faster and uses less memory for sparse mesh subsets (e.g. groups of clusters)
• meshopt_buildMeshlets* functions now support max_vertices=256 (up from 255)
• An experimental algorithm, meshopt_buildMeshletsFlex, allows more flexible cluster sizing and using axis-aligned bounds, which can improve clusterization quality for hierarchical clusterization and/or raytracing clusters
• An experimental algorithm, meshopt_computeSphereBounds, allows computing sphere bounds for groups of spheres or large meshes (as a complement to meshopt_computeMeshletBounds which is only useful for meshlets)
• An experimental algorithm, meshopt_partitionClusters, allows partitioning a set of clusters into larger groups, which is useful for hierarchical simplification
• meshopt_quantizeHalf/meshopt_quantizeFloat are now extern "C" to allow proper use from non-C++ code
• meshopt_simplifyWithAttributes, meshopt_simplifyPoints, meshopt_optimizeMeshlet, and meshopt_EncodeExpClamped are now stable
• CMake option MESHOPT_INSTALL allows disabling installation targets when building the library

gltfpack improvements

• Improve UV seam preservation for meshes with UV mirroring
• Implement support for KHR_materials_diffuse_transmission extension
• Allow disabling animation resampling by specifying frequency 0 (-af 0)
• Allow per-texture-class control for texture scaling (-ts) and limit (-tl)
• Preserve primitive extras when -ke is specified
• Warn when position quantization error is significant and -vpf is not specified

JavaScript changes

• simplifyWithAttributes and simplifyPoints no longer require MeshoptSimplifier.useExperimentalFeatures
• npm version of gltfpack now requires Node 18+ due to a WASI update

Thanks to @hankarun and @JulienIcon, as well as Nvidia engineers, for contributions to this release!