Gbuffers

Gbuffers, short for geometry buffers, are a collection of per-pixel data stored during a dedicated geometry pass in real-time rendering, primarily used by deferred shading pipelines. They separate the geometry stage from the lighting stage by recording scene information that lights will later use to compute shading. A G-buffer is typically implemented as multiple render targets, each storing a different per-pixel attribute. Common components include world-space or view-space position, per-pixel normals, albedo or diffuse color, and material properties such as specular color or the PBR parameters roughness, metalness, and ambient occlusion. Depth is usually stored in a separate depth buffer, but some pipelines include it in the G-buffer.

During the geometry pass, the renderer writes these values to the G-buffer as it rasterizes the scene. In the lighting pass, shaders read the G-buffer data to evaluate lighting contributions for every pixel, enabling scenes with many light sources without re-simulating geometry. This decoupling yields performance advantages when rendering complex lighting, allows post-processing effects to access per-pixel geometry data, and simplifies shadow, reflection, and global illumination techniques in some pipelines.

Trade-offs include higher memory bandwidth and storage requirements, potential challenges with transparency and MSAA, and the need for careful management of precision and formats. Gbuffers are foundational to many deferred shading implementations, with variants existing to balance fidelity, performance, and hardware support.