Monday, December 6, 2010

Rearranging code and some new thoughts

In the past week, most of the work was done in the back end. I re-arranged the code-base which had been pretty messy till last week. Basically, I had this giant main.cpp,, objLoader.cpp, a couple of header files and that's it. The main.cpp and were each over 1600 lines of code and it was really a magic to see all of this glued mess working. So I did lots of refactoring work, summarized as follows:
1. Scene graph related stuff was put into a SceneManager class. It references another class, KdTreeBuilder, which is in charge of Kd-Tree and photon mapping construction. It also implements a transformation-less scene graph, which are basically a mesh split into objects. Every time a transformation is done to the objects, the new coordinates are directly computed and embedded into the mesh, and Kd-Tree/Photon map is re-built on the fly.
2. Rendering related stuff was put into a RenderManager class. It keeps track of the current rendering settings (parameters, render methods, etc.)
3. The CUDA source,, was also split among rendering, helper methods and Kd-Tree building functions. Each kernel function has a wrapper C function that automatically sets up the block and thread settings for the kernels.

I also came up with an interesting idea to explore if I have enough time before the end of the semester. After reading Point-Based Approximate Color-Bleeding paper by Christensen et. al. (, I thought it would be interesting to see if this can be used on my renderer. The basic idea is to divide each polygons into small disks, or surfels, and arrange them into an octree. Whenever we need to compute indirect illumination on a point, we simply rasterize the surfels or octree nodes on a view cube around the point and then multiply the result by the surface BRDF. I would like to use ray trace for the direct illumination, kd-tree for surfel storage and same rasterization strategy and see what I can come up with.

Finally, a screen shot of the classic Cornell Box scene of a prototyped version that implements part of the paper mentioned above. Rendering takes 3 seconds on this 640x640 image with 200spp. More details will follow as I make more progress on this.

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