Graphics Reference
In-Depth Information
Figure 4.13. Convolved color texture of a simple scene with different level of convolution
at each level. This will be later used to create our rough reflections.
Usually to simulate this kind of blurred reflections in ray-tracing-based ren-
derers, we would shoot a lot of diverged rays defined by the cone aperture, say 32
more, and average the resulting colors together to produce a blurred reflection.
(See Figures 4.15 and 4.16.)
However, this quickly becomes a very expensive operation and the perfor-
mance decreases linearly with the number of rays we shoot, and even then the
technique produces noisy and unacceptable results that need further processing
to smooth out. One such technique is called image-space gathering [Robison and
Shirley 09], which works really well even on pure mirror reflections to make them
appear like rough reflections as a post-process.
Figure 4.14. Different levels of roughness on the spheres produce diverged reflection
rays, which results in the viewer perceiving blurred reflections. [Image courtesy of
[David 13].]
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