Classic DOOM with Ray Tracing in New Video

Youn said:
this isn't RTX? says so in the title but also looks like your darkplaces description
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No, that is not ray tracing. It is using a pixel shader to fake screen space lighting. Since it is in the pixel pipeline, it is not ray tracing. The author puts "RTX" in the title for clickbait.
 
Armenius said:
No, that is not ray tracing. It is using a pixel shader to fake screen space lighting. Since it is in the pixel pipeline, it is not ray tracing. The author puts "RTX" in the title for clickbait.
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I've heard this a lot about the RTGI shader, that it's "fake", not doing any path / ray tracing at all, but I have yet to see it definitively proven either way. Has Pascal Gilcher just been lying to his Patreon supporters and the entire ReShade community this whole time? My impression from following the project for a few years is that he figured out a way to use Depth Buffer data as an alternative to the traditional BVH and was abusing pixel shader functions to do compute in order to retain compatibility with DX9 and OGL. If it's really not doing any sort of ray / path tracing at all, I'm curious what is IS doing because it can move light and shadow around in a way that can be very convincing when the screenspace factor doesn't get in the way.
 
NattyKathy said:
I've heard this a lot about the RTGI shader, that it's "fake", not doing any path / ray tracing at all, but I have yet to see it definitively proven either way. Has Pascal Gilcher just been lying to his Patreon supporters and the entire ReShade community this whole time? My impression from following the project for a few years is that he figured out a way to use Depth Buffer data as an alternative to the traditional BVH and was abusing pixel shader functions to do compute in order to retain compatibility with DX9 and OGL. If it's really not doing any sort of ray / path tracing at all, I'm curious what is IS doing because it can move light and shadow around in a way that can be very convincing when the screenspace factor doesn't get in the way.
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It's calculating light after the frame has already been rendered. That is what I mean. "Real" ray tracing replaces the rasterization stage, happening between the geometry and pixel pipelines. "RTX" is being used as clickbait here because of NVIDIA's successful marketing to make normies equate all ray tracing to RTX, when in reality the RTGI shader is not using anything related to NVIDIA's proprietary middleware pipeline. The depth buffer is part of the rasterization pipeline. It isn't used with ray tracing unless it's in a hybrid rendering engine.
 
Armenius said:
No, that is not ray tracing. It is using a pixel shader to fake screen space lighting. Since it is in the pixel pipeline, it is not ray tracing. The author puts "RTX" in the title for clickbait.
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Ehh, it's still ray tracing, just done in post-processing, against a 2-ish-D object in a pseudo-3d space.
 
Armenius said:
It's calculating light after the frame has already been rendered. That is what I mean. "Real" ray tracing replaces the rasterization stage, happening between the geometry and pixel pipelines. "RTX" is being used as clickbait here because of NVIDIA's successful marketing to make normies equate all ray tracing to RTX, when in reality the RTGI shader is not using anything related to NVIDIA's proprietary middleware pipeline. The depth buffer is part of the rasterization pipeline. It isn't used with ray tracing unless it's in a hybrid rendering engine.
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Nobu said:
Ehh, it's still ray tracing, just done in post-processing, against a 2-ish-D object in a pseudo-3d space.
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"post-processing pixel shader effect that utilizes simplified path tracing in screenspace to generate a mask for applying luma/chroma data obtained from a rasterized image" has been my understanding of it and it seems we're all generally in agreement there.

FWIW, I think "RTX" is, for better or worse, well on its way to becoming a generic term
 
NattyKathy said:
FWIW, I think "RTX" is, for better or worse, well on its way to becoming a generic term
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I completely agree.
And I'm sure we'll still correct everyone, like those evil wine aficionados do with Sparkling Wine vs Champagne. With just as much interest by the receiving party. :)
 
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Nobu said:
Ehh, it's still ray tracing, just done in post-processing, against a 2-ish-D object in a pseudo-3d space.
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I mean, the same thing can be said for any 2.5D screen-space calculation in which Rays are traced, such as Crytek's SSAO implementation in Cryengine in 2007 and Screen-Space-Reflections found in just about every modern game engine since ~2011.

This is a screen-space effect, which means as soon as an object or light is off-screen, it does not contribute to the GI or lighting outside of pre-processed raster graphics. This method does see the game world, so it can't see shadow casters or indirect lights unless they are actively being looked at by the camera. It's cute but highly local and very unstable. A scene could appear lit completely differently based on the angle you approach it from and what light-and-shadow casters are on-screen.
 
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