AMD FidelityFX Brixelizer GI Is a Compute-Based Dynamic Global Illumination Solution Available Now in SDK 1.1

A new compute-based dynamic global illumination solution, AMD FidelityFX Brixelizer GI, has been released alongside SDK 1.1 (which also introduced AMD FSR 3.1).

AMD FidelityFX Brixelizer GI is based on the Brixelizer library, which generates sparse distance fields for triangle geometry in real time to effectively trace rays in a given scene. Brixelizer works with static and dynamic geometry, providing a shader API to trace rays against the distance field. It outputs cascades of sparse distance fields around a given position, with each cascade divided into 64x64x64 voxels. Once a voxel intersects any geometry, a local distance field is generated within the voxel. These local distance fields are called Bricks, hence the name of the technique.

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Its main goal is to provide a faster alternative to traditional DXR-based ray traced shadows and/or ambient occlusion. Depending on the size of the scene, it can offer a sizable performance boost, as shown in the comparison slide below.

To further improve performance, developers can increase voxel size to an extent. That will result in a coarser sparse distance field, which can be offset with increased ray bias.

AMD FidelityFX Brixelizer GI takes a game's G-Buffer and the sparse distance fields (SDFs) plus Bricks generated by Brixelizer to create Diffuse and Specular GI outputs. The sparse distance fields lack any material information, so there's an internal radiance cache based on the lighting output of previous frames. According to AMD, including the composited output from the previous frame effectively provides free multi-bounce global illumination. Then, screen probes are spawned on the depth buffer's visible surfaces. Rays are shot with Brixelizer, while the radiance cache is sampled for shading.

Ultimately, AMD FidelityFX Brixelizer GI is a