Coherency gathering in ray tracing: the benefits of hardware ray tracking

Despite the theoretically infinite ways to implement a modern GPU, the truly efficient ways to make one come to life in silicon tend to force the hands of those making them for real. The reality of manufacturing modern high-performance semiconductors, and the problem at hand when trying to accelerate the current view of programmable rasterisation, have uncovered trends in implementation across the GPU hardware industry.

For example, SIMD processing and fixed-function texture hardware are a cast-iron necessity in a modern GPU, to the point where not implementing a GPU with them would almost certainly mean it wasn’t commercially viable or useful outside of research. Even the wildest vision of any GPU in the last two decades didn’t abandon those core tenets. (Rest in peace, Larrabee).

Real-time ray tracing acceleration is the biggest upset to the unwritten rules of the GPU in the last 15 years. The dominant specification for how ray tracing should work on a GPU, Microsoft’s DXR, demands an execution model that doesn’t really blend in with the way GPUs like to work, giving any GPU designer that needs to support it some serious potential headaches. That’s especially true if real-time ray tracing is something they haven’t been thinking about for the last decade or so and here at Imagination, we have been.

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