Improving the Image Quality of Ray Tracing with 240Hz Displays

At SIGGRAPH 2019, NVIDIA’s Josef Spjut discussed best practices for real-time ray tracing when the display target is 240 Hz refresh rate monitors. The full talk, entitled “Ray Tracing at 240Hz”, can be viewed here.

“The computer can collaborate with the human visual system to integrate high quality images and video in the brain,” explained Spjut. “We use a combination of frameless and interleaved rendering concepts together with ideas from temporal antialising algorithms to trade spatial resolution for higher refresh rate and reduced spatiotemporal aliasing”.

240Hz monitors cater to professional gamers, eager to gain a competitive edge by playing at the lowest latency possible. While experimenting with 240Hz content for these new displays, Spjut and his team discovered something interesting: the quality of images improved well beyond expectations when shown at 240Hz. 

In the example below, Spjut took a camera, positioned it on a tripod, and set it to have a 16ms exposure time. He recorded an image – which is a 4x sample pattern that repeats for a single quad – in multiple scenarios: at 60Hz, 120Hz, and 240Hz. You can see jagged aliasing at 60Hz, but as the display reaches 240Hz, the aliasing goes down. 


To more clearly see the impact 240Hz has in reducing motion blur, aliasing, and noise, take a loot at the samples at 240hz.org on a 240hz monitor. 

“I believe this work is a precursor to a lot of very interesting high refresh rate rendering research,” said Spjut. 

To see a detailed breakdown on how running at 240Hz improves the perceptual experience, we encourage you to view the entire 30 minute talk. Spjut explains how he and his collaborators figured out an algorithm for faster rendering, getting a 4X speedup at ISO quality. The trick, as it turns out, involves adaptive pixel ordering selection.

For further study, please see the paper, “Temporally Dense Ray Tracing”. 

And if you have access to a 240Hz monitor, you’ll definitely want to check out the image samples available on 240hz.org


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