CPU vs GPU: A Discussion about Hardware Acceleration and Rendering

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(Interview of Prof. Dr. Philipp Slusallek, accomplished scientist and veteran from the computer graphics field, performed in January 2015 for Seekscale company, a cloud rendering startup) Hardware …
(Interview of Prof. Dr. Philipp Slusallek, accomplished scientist and veteran from the computer graphics field, performed in January 2015 for Seekscale company, a cloud rendering startup)

Hardware acceleration is hot in rendering industry right now, and while people still try to figure out how to split workloads between CPUs and GPUs, FPGAs are quickly rising. We interviewed Philipp Slusallek, Scientific Director and Computer Graphics professor at Saarland University, and talked about what's hot right now, and above all what we can expect in CG in the near future! We first heard about Philipp by coming across this great discussion.

– What rendering techniques are best adapted to each hardware (GPU/CPU)?

We basically have two key algorithms for rendering: rasterization and ray tracing. Rasterization is a "forward" rendering approach that renders the triangles in a scene one by one (conceptually) and each time updates all pixels covered by that triangle. Ray tracing, on the other hand, traces rays for each pixel to find out which triangle is visible for that pixel.

While the two seem very different, there are intermediate versions, such as "tile-based rasterization" or "frustum tracing", where only the triangles covering a part of the screen are rasterized or all rays of a tile a traced together, respectively. If you make these tiles smaller, eventually a single pixel in size, rasterization starts to look much like ray tracing and vice versa as you trace larger and larger frusta. However, we still do not have algorithms that really cover the whole range of options well.

Additionally, we are seeing an increased need for advanced (programmable) shading and lighting effects (e.g. global illumination for smooth indirect illumination). While they are sitting on top of the core renderer, they impose many requirements that will determine what rendering approach can or cannot be used.

On the HW (hardware) side: GPUs started as HW dedicated for rasterization. But they…
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