Graphics Reference
In-Depth Information
Cone aperture
Blurred reflection
Mirror reflection
Blurred reflection
a smooth surface
a rough surface
a very rough surface
Figure 4.15.
The rougher the surface is at a microscopic level, the more blurry and
weaker the reflection appears. Fewer rays hit the iris of the perceivers' eye, which gives
the weaker appearance. [Original image courtesy of [ScratchaPixel 12].]
Another drawback of shooting randomly jittered rays within the cone aperture
is the fact that parallel computing hardware such as the GPU tends to run threads
and memory transaction in groups/batches. If we introduce jittered rays we slow
down the hardware because now all the memory transactions are in memory
addresses far away from each other, slowing the computation by tremendous
amounts because of cache-misses and global memory fetches, and bandwidth
becomes a bottleneck.
Rough material surface
8 samples
Rough material surface
32 samples
Figure 4.16.
Noisy reflections produced by firing multiple diverged rays and averaging
the results together for glossy reflections. Even 32 rays per pixel are not enough to
create a perfectly smooth reflection and the performance decreases linearly with each
additional ray. [Original images courtesy of [Autodesk 09] and [Luxion 12].]
