In between end of year celebrations, nights in hotels because of cancelled flights and other snow storms, I still managed to progress on the layered material representation front.
Stanford Dragon, diffuse material coated with glass.
I admit that it is not the most spectacular example as it does not show off the effect of absorption in the glass coat… But at the moment I cannot be asked to wait 20+ hours to re-render.
Dielectrics with Beer's Law.
Dielectrics and Beer’s Law are now integrated into the materials and environment frameworks. In the picture above the indices of refraction increase from left to right.
Reflection functions
I have been experimenting with BRDFs lately.
In the picture above, from left to right: Oren Nayar, Torrance-Sparrow with different roughness, and smooth dielectrics.
In addition to having a first (very limited) framework for material representation and rendering, I have just added support for convex quadrilaterals.
Both features are combined below in a Cornell Box test (using original spectral and dimension data).
Cornell Box
I am investigating how to represent materials in the core engine. Obviously it should be as physically correct as possible.
Here is my current wish list. The material representation should:
From readings and thoughts, I think that requirement no. 2 pretty much implies some sort of layered model to combine simple building blocks into a complex material. This is the route I am following at the moment.
As for references, I have grabbed a copy of Digital Modeling of Material Appearance by Dorsey, Rushmeier and Sillion, which in my opinion gives a good theoretical overview of the topic. And, of course, I am roaming the web for academic papers.
Regarding reference implementations, the PBRT book seems to give the most complete example.