Radiance is a physically-based rendering system developed by Gregory J. Ward at the Lawrence Berkeley Laboratory and the Ecole Polytechnique Federale de Lausanne. It is designed for accurate lighting simulation and visualization, with a focus on architectural and lighting design. The system uses a light-backwards ray-tracing method to solve the rendering equation efficiently, supporting specular, diffuse, and directional-diffuse reflection and transmission in any combination. It blends deterministic and stochastic ray-tracing techniques to balance speed and accuracy. The system's design goals include accurate luminance calculation, modeling both electric light and daylight, supporting various reflectance models, handling complex geometries, and accepting unmodified input from CAD systems. Radiance has been validated through physical measurements and has been widely adopted by the research and design community. It has been used by design companies to replace their in-house software, demonstrating its practicality and effectiveness. Radiance uses a hybrid deterministic/stochastic ray-tracing approach to solve the rendering equation, which involves calculating the reflected radiance at each surface point. It employs cached indirect irradiances for diffuse interreflection to reduce computational costs, using gradient information to improve interpolation accuracy. Adaptive sampling of light sources is used to reduce the number of shadow rays, improving efficiency. Virtual light sources are introduced to handle reflections from specular surfaces, and secondary light sources are used to treat daylight contributions more efficiently. Radiance also uses hierarchical octrees for spatial subdivision, allowing efficient handling of complex geometries. Patterns and textures are used to add detail to scenes, and parallel processing is implemented to reduce calculation time. The system supports animation by using recorded depth information and illumination maps, enabling efficient frame generation. Radiance is a collection of C programs that communicate via standard data types, ensuring portability and compatibility across systems.Radiance is a physically-based rendering system developed by Gregory J. Ward at the Lawrence Berkeley Laboratory and the Ecole Polytechnique Federale de Lausanne. It is designed for accurate lighting simulation and visualization, with a focus on architectural and lighting design. The system uses a light-backwards ray-tracing method to solve the rendering equation efficiently, supporting specular, diffuse, and directional-diffuse reflection and transmission in any combination. It blends deterministic and stochastic ray-tracing techniques to balance speed and accuracy. The system's design goals include accurate luminance calculation, modeling both electric light and daylight, supporting various reflectance models, handling complex geometries, and accepting unmodified input from CAD systems. Radiance has been validated through physical measurements and has been widely adopted by the research and design community. It has been used by design companies to replace their in-house software, demonstrating its practicality and effectiveness. Radiance uses a hybrid deterministic/stochastic ray-tracing approach to solve the rendering equation, which involves calculating the reflected radiance at each surface point. It employs cached indirect irradiances for diffuse interreflection to reduce computational costs, using gradient information to improve interpolation accuracy. Adaptive sampling of light sources is used to reduce the number of shadow rays, improving efficiency. Virtual light sources are introduced to handle reflections from specular surfaces, and secondary light sources are used to treat daylight contributions more efficiently. Radiance also uses hierarchical octrees for spatial subdivision, allowing efficient handling of complex geometries. Patterns and textures are used to add detail to scenes, and parallel processing is implemented to reduce calculation time. The system supports animation by using recorded depth information and illumination maps, enabling efficient frame generation. Radiance is a collection of C programs that communicate via standard data types, ensuring portability and compatibility across systems.