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DLSS 4.5 has proven to be an impressive upgrade over DLSS 4.0 in some areas. Not only does the new model provide superior upscaling quality, but it can also outright improve the visual fidelity of 3D graphics. Building on the latter, Digital Foundry discovered that both DLSS 4.5 Presets M and L are capable of reconstructing ray-traced reflections almost perfectly (depending on the game), as long as in-game denoisers are turned off.
Digital Foundry saw this behavior in Crysis 3 and Silent Hill 2, where DLSS 4.5 produced noticeably better ray-traced image quality with each game's denoiser turned off compared to with them turned on. In Crysis 3, turning off the engine's denoiser resulted in less boiling, and in Silent Hill 2, turning off the denoiser resulted in a night-and-day difference in reflection quality — to the point where there was almost no image blurring or boiling to be seen.
DLSS 4.5 Preset L Review: Nvidia's Most Advanced Upscaler Tested At 4K And 1440p - YouTube
Boiling and image noise are problems that ray-traced effects naturally produce. Game developers use denoisers to remove these artifacts. However, one caveat with these filters is that they generally do not produce a perfect image. This is why you'll find objects or textures in ray-traced reflections looking oily or smeared.
NVIDIA introduced DLSS Ray Reconstruction to help solve this problem, and Ray Reconstruction itself generally provides better image quality with AI, compared to the capabilities of traditional denoisers. This has especially been the case with DLSS 4's Ray Reconstruction transformer model, which produces noticeably superior image quality compared to the initial DLSS 3.5 version.
What we are seeing with DLSS 4.5 is very unique. NVIDIA has tuned the transformer model of its DLSS upscaler so well that it alone can remove the aforementioned artifacts that ray tracing effects generate naturally. Also, DLSS 4.5 is doing this without Ray Reconstruction — since Ray Reconstruction has not yet been updated to support the newer DLSS 4.5 model.
If Nvidia can fully leverage this feature and improve it, we could very well see it stop supporting Ray Reconstruction (or, rename it and bake it into the upscaler portion of DLSS instead, at a future date). This would simplify DLSS and make life potentially easier for developers to incorporate DLSS into ray tracing games, as they would not need to worry about Ray Reconstruction integration.
However, this will all depend on how effective DLSS 4.5 is at denoising. Digital Foundry is the only outlet we've seen so far that's covered this behavior in-depth, and it has only covered it in just two titles. There could be issues with DLSS 4.5's denoising capabilities in other ray tracing games and/or effects that we are not aware of at this point. Also, DLSS 4.5 handles upscaling with in-game denosing turned on worse, compared to DLSS 4. This is critical since not all ray-tracing games officially allow gamers to disable a game's built-in denoiser.
Somebody needs to tell the author that ray reconstruction applies to path tracing and is necessary to get the current level of performance. Traditional single bounce ray tracing doesn’t need it in the first place.
