Graphics Reference
In-Depth Information
Figure 4.12.
Hi-Z ray-tracing step by step going up and down in the hierarchy of the
buffer to take longer jumps at each step. [Source image courtesy of [Drobot 09].]
4.4.4 Pre-convolution Pass
The pre-convolution pass is an essential pass for the algorithm for computing
blurred glossy reflections emitted from microscopic rough surfaces. Just like in
the Hi-Z pass, which outputs a hierarchy of images, this pass also does so, but
with a different goal in mind.
We convolve the original scene color buffer to produce several different blurred
versions out of it as we can see in Figure 4.13. The final result is another hier-
archical representation, images at different resolutions with different levels of
convolution, which is stored in the mip-map channels.
These blurred color buffers will help out with accelerating rough reflections
to achieve results similar to what we can see in Figure 4.14.
