Today there will be a presentation by CDPR about the ray tracing mode in Cyberpunk 2077 called Overdrive, which is supposed to ignite the next level of realism in games thanks to path tracing. In advance, a video shows which screws developers can turn.
SER for better performance with path tracing
Nvidia uses the GDC to provide updated tools for developers. In addition to a first SDK for path tracing, there was also an update for DLSS3: There is SDK version 3.1.10 on Github, which is supposed to bring more performance and better stability. Efficiency is the keyword here, because in order to implement path tracing in a game like Cyberpunk 2077 (buy now €74.89), some optimizations are necessary. A GDC presentation shows how the Nvidia Nsight Graphics tool was used to optimize path tracing in Cyberpunk 2077 to identify and fix shader inefficiencies. The implementation of Shader Execution Reordering (SER), an RTX 40 feature, has “significantly improved” path tracing efficiency, according to the video.
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Shader Execution Reordering (SER) is another efficiency function that is supposed to help ray tracing calculations. The feature is able to pre-sort the work instructions that arise diffusely, especially with complex ray tracing, so that the shading can be carried out more efficiently and without “air bubbles” in the pipeline. But SER needs manual work by the developers.
The video shows an NSight graphics profile of Cyberpunk 2077 captured on an RTX 4090 graphics card. With the GPU trace you can analyze the throughput per frame and thus get an overview of the GPU time for performance characteristics involved in rendering the game. So you can see that the lighting takes up a large part of the frame’s render time and that DispatchRays is the main culprit. DispatchRays starts a shader’s threads for ray generation.
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According to Nvidia, the trace analysis can detect the inefficiency and provide recommendations for solving the problem. Here the optimization for active threads offers a high potential for speeding up the frame to speed up path tracing. By using the SER API in Cyberpunk 2077, DispatchRays run faster, and the required GPU processing time on the RTX 4090 has been reduced by about 42 percent overall, according to Nvidia.
More details today
As a reminder, at the GDC developer fair today there is a presentation on how Nvidia and CD Projekt are bringing red path tracing to Cyberpunk 2077’s Night City. Overdrive mode is promised to “take the next level” in visual realism thanks to RTX path tracing. Cyberpunk is already one of the most technically demanding games on the market thanks to its huge world and visual variety. The neon-lit environments and expansive vistas of Night City are “already pushing the limits of what’s currently possible in real-time graphics.”
A path tracing renderer enables what was previously (virtually) not feasible in games: A completely dynamic and comprehensive, physics-based simulation of the light in an equally dynamic scene. In contrast to most previous games with hybrid ray tracing, where mostly only individual effects such as reflections or individual shadows are displayed using ray tracing, the complete light calculation is carried out with path tracing.
