Edge-avoiding À-Trous wavelet transform for fast global illumination filtering

We present a fast and simple filtering method designed for ray traced Monte Carlo global illumination images which achieves real-time rates. Even on modern hardware only few samples can be traced for interactive applications, resulting in very noisy outputs. Taking advantage of the fact that Monte Carlo computes hemispherical integrals that may be very similar for neighboring pixels we derive a fast edge-avoiding filtering method in screen space using the A-Trous wavelet transform that operates on the full noisy image and produces a result that is close to a solution with many more samples per pixel.