BRDF Explorer is an application that allows the development and analysis of bidirectional reflectance distribution functions (BRDFs). It can load and plot analytic BRDF functions (coded as functions in OpenGL's GLSL shader language), measured material data from the MERL database, and anisotropic measured material data from MIT CSAIL. Graphs and visualizations update in realtime as parameters are changed, making it a useful tool for evaluating and understanding different BRDFs (and other component functions).
MotivationIn the pursuit of visual realism in our films, we have spent a considerable amount of time exploring the strengths and weaknesses of different BRDFs. To understand the properties of different BRDFs, we found it helpful to be able to visualize and graph them in different ways to see how they responded to illumination in different configurations. Additionally, we wanted to compare BRDFs to sampled BRDF data (mainly those in the MERL BRDF Database). We developed BRDF Explorer because at the time, no publicly available tool met our needs (although BRDFLab, which has since been released, has some similar capabilities).
ScreenshotA screenshot is worth a thousand words:
Get StartedYou can get the source code or win32 binary at github. The source is licensed under the MS-PL (Microsoft Public License).
The only dependencies are Qt, OpenGL, and a relatively recent GPU - we haven't verified the requirements, but anything supporting DX10 / Pixel Shader 4.0 will probably be fine. While there's nothing platform-specific in this code, we have only extensively tested under Linux.
Future PlansWe plan to add Multiple Importance Sampling (MIS), in addition to the IBL importance sampling already there. Alternative BRDF representations (such as additional sampled format types) and additional graphs and views will be added as needed.
More Ptex ProbesPaul Debevec has graciously allowed us to offer his light probes in Ptex format which can be used with BRDF Explorer:
Download (20.2 MB zip file)
HDR Light Probe Images © 1988 courtesy of Paul Debevec, www.debevec.org, used with permission. Also see: