Ray Tracey's blog: Comparing path tracing image quality

Friday, April 23, 2010

Comparing path tracing image quality

After seeing the amazing videos of the "Brigade" engine", the realtime pathtracer developed by Jacco Bikker, I was wondering what would be the ideal parameters (resolution, framerate and samples/pixel) for a pathtraced game with today's hardware. I decided to do some simple experiments by comparing the image quality of a path traced scene in samples/pixel. I found two youtube videos of reasonable quality showing some moderately complex scenes rendered in Octane render and took some screensgrabs. The lighting and materials are very simple and the video and jpeg compression do not allow a good comparison, but anyway here's a rough idea:

Video 1: Porsche Carrera rendered with Octane

2 samples/pixel

6 samples/pixel

12 samples/pixel

24 samples/pixel

36 samples/pixel

1 sample/pixel

8 samples/pixel

16 samples/pixel

24 samples/pixel

40 samples/pixel

1 sample/pixel

8 samples/pixel

16 samples/pixel

32 samples/pixel

64 samples/pixel

96 samples/pixel

Video 2: Chalet/Hotel rendered with Octane

1 sample/pixel

8 samples/pixel

16 samples/pixel

32 samples/pixel

As these pictures show, the noise clears very fast at the beginning, but the image converging slows down rather quickly, following a saturation curve

8 samples/pixels is too noisy to see fine details, at 16 samples/pixels details start to appear and 32 samples/pixel gives sufficient quality for a game imo (compared to the horribly lowres shadow maps and normal maps in some of today's AAA games, like Modern Warfare 2). Unfortunately, the youtube video and subsequent jpeg compression makes the difference between 64 and 96 samples/pixel indiscernible. More than 100 samples/pixel would be ideal, but for now 32 will do. Hopefully the Fermi GPU (or multiple) will get us there soon.

UPDATE: I made a shitload of screengrabs (way too much) from this video (HD footage of the Brigade engine)

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