Chakravarty R. Alla Chaitanya,
Proceedings of High Performance Graphics 2017
Our filter takes (left) 1 sample per pixel path-traced input and (center)
reconstructs a temporally stable 1920x1080 image in just 10ms. Compare to
(right) a 2048 samples per pixel path-traced reference. Insets compare
our input, our filtered results, and a reference on two regions, and show
the impact filtered global illumination has over just direct illumination.
Given the noisy input, notice the similarity to the reference for glossy
reflections, global illumination, and direct soft shadows.
We introduce a reconstruction algorithm that generates a temporally stable
sequence of images from one path-per-pixel global illumination. To handle
such noisy input, we use temporal accumulation to increase the effective
sample count and spatiotemporal luminance variance estimates to drive a
hierarchical, image-space wavelet filter. This hierarchy allows us to
distinguish between noise and detail at multiple scales using local
Physically based light transport is a long-standing goal for real-time
computer graphics. While modern games use limited forms of ray tracing,
physically based Monte Carlo global illumination does not meet their
30Hz minimal performance requirement. Looking ahead to fully
dynamic real-time path tracing, we expect this to only be feasible using
a small number of paths per pixel. As such, image reconstruction using low
sample counts is key to bringing path tracing to real-time.
When compared to prior interactive reconstruction filters, our work
gives approximately 10x more temporally stable results, matches reference
images 5-47% better (according to SSIM), and runs in just
10ms (+- 15%) on modern graphics hardware at 1920x1080 resolution.