# meshoptimizer 1.1: Meshlet Compression and Opacity Micromaps
The new version of the meshoptimizer 1.1 library adds a codec for meshlet compression and support for generating opacity micromaps. The update focuses on topology optimization for GPU rendering and accelerating ray tracing. Development is in C++ and JavaScript under the MIT license, with primary contributions from Valve.
Triangle Mesh Optimization
The meshoptimizer library improves vertex and index processing in the GPU pipeline stages. Algorithms reduce mesh complexity, minimize storage costs, and boost rendering efficiency. Since 2017, the project has evolved, with version 1.0 released in December 2025.
Related tools:
- gltfpack: CLI utility for automatic optimization of glTF files.
- clusterlod.h: C/C++ library for clustered LOD with continuous level of detail.
Meshlet Compression Codec
The new codec compresses meshlet topology by exploiting the locality of micro-indices and vertex data. Each meshlet is encoded independently, simplifying parallelism and runtime storage structure.
Decoding is optimized for high speed:
- CPU: 7–10 GB/s on desktop processors, works with write-combined memory.
- GPU: >150 GB/s on RTX 5070 via compute shader.
Output data is further compressed with Zstandard. The decoder generates formats of 3/4 bytes per triangle and 2/4 bytes per vertex for direct GPU use.
Opacity Micromaps
Functions generate hardware-ready micromaps from mesh UV coordinates and alpha texture. Support for Vulkan (VK_EXT_opacity_micromap) and DirectX (DXR 1.2).
Each triangle is divided into 4^N micro-triangles along UV. Representation options:
- 2-state (1 bit): complete elimination of shader calls for maximum ray tracing performance.
- 4-state (2 bits): acceleration of any-hit shaders via texture lookup.
Reusing maps between triangles via OMM index buffer minimizes memory. For 4-states, a fallback to 2-states is available.
Key Points
- Meshlet codec provides decompression at 7–10 GB/s on CPU and >150 GB/s on GPU.
- Micromaps generated from UV and alpha, compatible with Vulkan/DirectX.
- Independent meshlet encoding simplifies parallelism and runtime storage.
- Support for 1/2-bit states for optimizing ray tracing and shaders.
- Additional Zstandard compression for final size.
The update targets mid/senior developers working with GPU rendering and ray tracing in game engines. Integration requires no changes to existing pipelines.
— Editorial Team
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