Physically Based Rendering

A rendering approach that models light and materials according to real optics, so objects look believable under any lighting.

PBR refers to rendering methods that describe light sources and surface materials according to real-world optical principles. The term emerged in the 1990s, spread through Pharr and colleagues' textbook of the same name, and was later pushed into real-time rendering by Disney and Epic Games; it is now the standard approach in Unreal, Unity, and Blender. It generally satisfies three conditions: surface roughness is described with a microfacet model; energy is conserved, so a surface never reflects more light than it received; and reflectance follows a physically valid BRDF (the function describing how a surface reflects light). Materials are typically described with maps for base color (albedo), normal, metallic, and roughness. When a simulator uses PBR materials, the reflections and highlights in camera views come much closer to reality, which is one precondition for narrowing the visual sim-to-real gap.

ExampleFor the same stainless-steel pot, setting metallic to 1 and lowering roughness renders sharp highlights and clear environment reflections; raising roughness instead gives it a brushed, matte look.

Also called

PBR, PBR Materials, Metallic-Roughness Workflow

Related

Path Tracing · Ray Tracing · Rendering · Photorealistic Rendering · SimReady Assets · Sim-to-Real Gap (Reality Gap)

Sources

Wikipedia: Physically based rendering
LearnOpenGL: PBR Theory
Physically Based Rendering: From Theory to Implementation, 4th ed. (online)