The RADIANCE Lighting Simulation and Rendering System

Gregory J. Ward /


1. Introduction

2. System Design Goals

2.1 Ensure Accurate Calculation of Luminance

2.2 Model Both Electric Light and Daylight

In order to be general, a lighting calculation must include all significant sources of illumination. Daylight simulation is of particular interest to architects, since the design of the building facade and to a lesser degree the interior depends on daylight considerations.

Initially, Radiance was designed to model electric light in interior spaces. With the addition of algorithms for modeling diffuse interreflection [25], the software became more accurate and capable of simulating daylight (both sun and sky contributions) for building interiors and exteriors. The role of daylight simulation in Radiance was given new importance when the software was chosen by the International Energy Agency (IEA) for its daylight modeling task [4].

2.3 Support a Variety of Reflectance Models

2.4 Support Complicated Geometry

2.5 Take Unmodified Input from CAD Systems

3. Approach

3.1 Hybrid Deterministic/Stochastic Ray Tracing

3.2 Cached Indirect Irradiances for Diffuse Interreflection

3.3 Adaptive Sampling of Light Sources

3.4 Automatic Preprocessing of "Virtual" Light Sources

3.5 User-directed Preprocessing of "Secondary" Sources

3.6 Hierarchical Octrees for Spatial Subdivision

3.7 Patterns and Textures

3.8 Parallel Processing

3.9 Animation

3.10 Implementation Issues

4. Applications and Results

4.1 Electric Lighting

4.2 Daylighting

5. Conclusion

6. Acknowledgements

7. Software Availability

8. Bibliography

9. Appendix