pBR

Physically Based Rendering (PBR) is a shading approach used in computer graphics to simulate how light interacts with real-world materials. Its aim is to produce images that look plausible under a wide range of lighting conditions by enforcing physical plausibility and energy conservation.

PBR relies on a small set of material properties and a physically based lighting model. The core idea is to separate how a surface reflects light from how that light is produced, using microfacet theory and Fresnel effects to approximate real materials. The result is more consistent appearance across different environments and camera angles than older, purely empirical shading models.

Materials in PBR are typically described with maps and a few core parameters. The metallic-roughness workflow is the most common today: base color (albedo), a metallic map (metal vs non-metal), a roughness map (surface microfacet roughness), plus normal or height maps and often an ambient occlusion map. Subsurface scattering is handled separately for specialized materials. A second, less common specular-glossiness workflow is still seen in some pipelines.

Lighting in PBR uses physically plausible BRDFs, usually a Cook–Torrance model with a microfacet distribution (commonly GGX) and Fresnel terms. Realistic results are often achieved with image-based lighting, where environment maps provide distant illumination that is prefiltered for roughness levels.

PBR has been widely adopted in real-time engines such as Unreal Engine and Unity, as well as in offline rendering. While it improves consistency and realism, it depends on accurate material definitions, proper color spaces, and appropriate lighting to avoid perceptual inconsistencies.