Autodesk 12812-051462-9011 User Guide 3 - Page 929

The renderer calculates the direct lighting and shadows and then integrates the radiosity solution (indirect lighting) as a modulated ambient light. Lighting Analysis After you generate a radiosity solution, you can use the Lighting Analysis tool on page 6219 to analyze the lighting levels in your scene. This dialog provides data on material reflectance, transmittance, and luminance. You can also visualize the light levels in the scene interactively with the Pseudo Color Exposure Control on page 6753. Rendering to the Rendered Frame Window displays an additional rendered frame with a legend below the image. The legend correlates lighting levels and color values. If you need to generate a lighting report, you can use the Lighting Data Exporter utility on page 6759 to export the luminance and illuminance data to a 32-bit LogLUV TIFF file on page 7372 or a pair of PIC files on page 7359 (one each for luminance and illuminance). NOTE To obtain the most accurate quantitative analysis of lighting levels, avoid using colored materials and diffuse maps. Non-Physically Based Workflow You don't necessarily have to work with physically based lights and materials in order to incorporate radiosity effects into your renderings. But there are a number of issues that you need to consider: ■ Lights: Because the radiosity engine is physically based, the engine interprets Standard lights on page 5049 as Photometric lights on page 5005. For example, a Standard Spot light with a multiplier value of 1.0 is translated as a Physically Based Spot light with an intensity value of 1500 candelas (default value). This translation value corresponds to the Physical Scale value in the various exposure controls. In addition, if your Standard lights use custom attenuation settings (for example, no attenuation, manual attenuation, or linear decay), the radiosity engine always solves for these lights using inverse square attenuation, which is physically correct. This means that the amount of energy that bounces between surfaces might not be equivalent to the way the Standard lights render. 6184 | Chapter 20 Rendering