Physically based rendering (PBR) is a modern approach to computer graphics that simulates the interaction of light with materials in a physically accurate manner. It aims to achieve photorealistic results by incorporating complex mathematical models and real-world material properties.

Traditional shading models, such as Phong or Blinn-Phong, use simplified equations for calculating lighting and reflections, which can result in unrealistic appearances. PBR, on the other hand, relies on principles from physics, like conservation of energy and microfacet theory, to produce more believable visuals.
In terms of realism, PBR surpasses traditional shading models due to its ability to replicate how light behaves in the real world. This includes accurately depicting effects like Fresnel reflections, roughness, and metallicity, leading to more convincing images.

However, PBR’s increased realism comes at the cost of performance. The complex calculations required for PBR demand more computational resources than simpler shading models. As a result, PBR may not be suitable for all applications, particularly those with limited hardware capabilities or strict performance requirements.

Despite these challenges, advancements in GPU technology have made PBR increasingly accessible, allowing artists and developers to create stunningly realistic visuals without sacrificing performance in many cases.