Archive for March, 2012
Sampling Sun And Sky
In this post I will briefly cover how I implemented sampling of external light sources in a path tracing framework, concluding with an observation about sampling multiple external light sources that are non-zero over very different solid angles. I’m going to assume the reader is familiar with path tracing in the Veach framework.
My definition of an external light source, which I’ve also seen called an “infinite” light source since they are considered to be infinitely far away (and infinitely bright as a result), is as follows:
- Radiance always originates from outside of the scene bounds
- Radiance is a function of world space direction only (not sample position)
A simple example would be a cube map considered to be always centered at the sample point.
SketchUp Cities
Ray Tracey’s latest blog post has Brigade 2 renders of a nice-looking walled city scene created using Google SketchUp. The model came from this gem of a collection by “LordGood” (who evidently is a big Assassin’s Creed fan) hosted on Google 3D Warehouse.
Currently I only have a Blender exporter, and sadly the SketchUp-Collada-Blender path was producing garbage, but even the free version of SketchUp allows custom ruby plugins. After a bit of hunting around I found this OBJ exporter ruby plugin which worked very well, and now I have much nicer test meshes than my bad Blender programmer art.
The above images are from my usually-being-refactored path tracer with Preetham (et al) sun/sky. It doesn’t render as quickly as Brigade 2 (also I only have a lowly GTX 460 to render on), and yes it’s all diffuse and I haven’t exported any of the textures, and there’s no atmospheric terms or depth of field or shading normals or remote-controlled Stanford bunny, but it’s nice to have some decent public domain data to use.
I’m slowly working on a Bidirectional Instant Radiosity post (hopefully using this scene) but it’ll have to wait until work is less mental.
