Ray tracing has been one of NVIDIA’s big bets in the graphic sector, both professional and general consumption, although it has been accompanied by a secondary luxury player, artificial intelligence, whose most important implementation so far we have seen, in terms of games, in the DLSS technology.

When NVIDIA introduced the Turing architecture and started talking about ray and pixel tracing there was great skepticism around it, something understandable since the ray tracing applied by pixel generates enormous demands that, in the end, could not be overcome in the present generation, although I must say that we have had the opportunity to see some interesting results in games like Metro: Exodus, which offers very realistic global lighting, and in Wolfenstein Youngblood, which shows very careful reflections, both thanks to ray tracing.

DLSS technology, NVIDIA algorithm-based smart rescaling (artificial intelligence), came with the intention of compensating for this enormous demand in terms of graphic power that ray tracing represents. Its starting point is as simple as it is successful, rendering at a lower resolution and rescaling to reduce the number of pixels on the screen, analyzing multiple frames to create the “perfect rescaled image”. DLSS 1.0 did not achieve a good result, but DLSS 2.0 did, so this technology is viable and very promising.

ReSTIR: a new algorithm to demonstrate the potential of ray tracing

Ampere will mark the next turning point at the hardware level when it comes to ray tracing, and we can say that ReSTIR could be its equivalent in the software field. We are dealing with an algorithm that has been developed by the NVIDIA research department, capable of rendering direct dynamic lighting and shadows from millions of light sources in real time, and with a latency between frames less than 50 ms.

This algorithm is between 6 and 60 faster than all previous equivalent technologies, and the best thing is that it works without problems in the current generation of NVIDIA, that is, in the GeForce RTX series 20. It is not, therefore, an exclusive thought only to work with the 30 series RTX, which will be based on Ampere. This architecture promises, according to the latest leaks, a performance improvement with ray tracing of up to 400% vs. Turing.

ReSTIR works by continuously resampling a set of selected light samples, on which it applies a new spatial and temporal sampling taking advantage of the information obtained from other nearby samples that are considered relevant. Said in a simpler way, reuses information from adjacent pixels spatially and temporarily to decide which rays should follow and take advantage of the existing information.

As we can see in the video the result is fantastic. We have scenes with up to 3.4 million dynamic triangles, a path of up to 8 rays per pixel and more than acceptable latency between frames. The train station demo was run on an RTX 2080 Ti, but the amusement park demo had to be run on a TITAN RTX for graphics memory reasons, as the former did not have enough.

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