This assigment is similar to the last one...an initial heirarchical radiosity system was created using the same technique as homework #5, but with a much higher error tolerence. This tolerence was decreased over several iterations, which involved refining the current system using information from the last solution step performed.

I decreased the error threshold by a factor of 2 for each iteration. The error term was calcualted by using the surface area of the element times the estimated form factor error and weighting this by an estimated visibility error. This forced more detail to be created at shadow boundries. Again 16 samples were performed for both form factor estimation and visibility testing. I performed 8 iterations, which is a number I selected since at 9 interations I really couldn't see much changing. Each refinement pass solved the current system of links by performing 4 GatherSweep passes.

I actually used two different methods for performing the interations. The first method continued to refine a system at a given error threshold until no more refinement was possible.

10272 interactions after initial building pass (4.71209 sec)
11169 interactions after pass 1 (8 refinement steps, 0.870864 sec)
13736 interactions after pass 2 (12 refinement steps, 2.30245 sec)
16554 interactions after pass 3 (6 refinement steps, 2.08483 sec)
20075 interactions after pass 4 (12 refinement steps, 4.51056 sec)
23391 interactions after pass 5 (8 refinement steps, 4.33571 sec)
27669 interactions after pass 6 (4 refinement steps, 4.40912 sec)
34291 interactions after pass 7 (4 refinement steps, 6.31922 sec)
43260 interactions after pass 8 (7 refinement steps, 12.2375 sec)
Total elapsed time: 41.7823 sec

The second method simply performed one refinement step per iteration. The results were surprisingly similar.

10272 interactions after initial building pass (5.0312 sec)
10938 interactions after pass 1 (1 refinement step, 0.395807 sec)
12909 interactions after pass 2 (1 refinement step, 1.0565 sec)
15481 interactions after pass 3 (1 refinement step, 1.3875 sec)
18059 interactions after pass 4 (1 refinement step, 1.42313 sec)
21485 interactions after pass 5 (1 refinement step, 1.89526 sec)
26168 interactions after pass 6 (1 refinement step, 2.78414 sec)
32825 interactions after pass 7 (1 refinement step, 4.02955 sec)
40138 interactions after pass 8 (1 refinement step, 4.61106 sec)
Total elapsed time: 22.6142 sec