Explicit vectorization

[gnzlbg]

Consider using the packed_simd crate for explicit vectorization to, e.g., process multiple rays at once using SIMD instructions.

The packed_simd examples/ directory contains a ray-tracing example that implements ambient occlusion using explicit vectorization and rayon for parallelization.

[wahn]

Thanks for the suggestion. I will look into it at some point, but the main motivation was to be as close to the original source code. Once the code base between C++ and Rust is more or less the same I might do some additional improvements. It's also important at this stage to be able to run debug code on both the C++ and the Rust side to work on pixel by pixel matches. But further SIMD optimizations are on the horizon ... Thanks again.