3 ms·

I tried to figure out whether the new GI used raytracing, and it doesn't seem like it is? If it is using raytracing hardware it isn't nearly as impressive. If i

by _bxg1 6y ago

I tried to figure out whether the new GI used raytracing, and it doesn't seem like it is? If it is using raytracing hardware it isn't nearly as impressive. If it isn't, then it's sheer magic.

skohan 6y ago
I'm almost certain they are. HW raytracing is of the big selling points of the new console generations, and if they achieved these kinds of results without it, then I would have to reconsider my skepticism of the occult.
- paavohtl 6y ago
  It was confirmed[1] in a Digital Foundry interview that the demo is NOT using HW raytracing. [1] https://www.eurogamer.net/articles/digitalfoundry-2020-this-is-next-gen-unreal-engine-running-on-playstation-5 https://www.eurogamer.net/articles/digitalfoundry-2020-this-...
  - skohan 6y ago
    That's incredible. I look forward to learning more about how they do it
- deleted 6y ago
  [deleted]
olavgg 6y ago
Shadows are too sharp, so I don't think they use raytracing.
- _bxg1 6y ago
  It certainly isn't completely raytraced, because current hardware can't support that. If they use the new hardware, they're using it in some kind of mixed mode. Whether that means only for certain materials, or whether they're able to use it to do "fat rays" that approximate only the general direction for indirect light, or whatever else. But direct, hard shadows are quite cheap (comparatively) on today's regular, rasterization-based rendering systems, so that part isn't surprising.
  - skohan 6y ago
    It certainly isn't fully path traced, but the result does look to me like they are using ray-traced GI. You can tell by some of the details, like colored bounce lighting which I am not sure can be achieved with this level of detail using other methods. The current standard for getting real-time performance for ray tracing is to limit the number of rays and bounces, and stabilize the results temporally. I.e. to get a "physically accurate" result you would have to send hundreds, or thousands of rays per pixel, and bounce them up dozens or hundreds of times. With this method, instead you send maybe even one or two rays per pixel, which gives you a noisy result. But you store the result, and accumulate it over a number of frames, and apply de-noising, and over time you end up with a high-quality result. I believe that is why when the light moves, the GI lags for a fraction of a second in this demo.
    - longtom 6y ago
      Another trick is in stead of tracing multiple bounces per ray at once, to compute one indirect bounce every n-th frame using intermediate results from the previous (not the current) frame and then spatio-temporally smooth the results, possibly with on-screen bilateral filtering of the past few frames. I think one can see they do this when they move the light source. It takes a while for the indirect bounces to fade out. Perhaps they use screen space ray tracing for this (meaning no indirect bounces for occluded geometry).
- skohan 6y ago
  Why would sharp shadows rule out raytracing? And how would they achieve this quality of GI without it?
  - longtom 6y ago
    Because softer shadows add to the realism, so they would have used them if they had invented a new efficient ray tracing method! Look at 5:12 in the video. The shadows are way too sharp. It's probably good old shadow mapping for the first bounce and then screen space(?) global illumination.
deleted 6y ago
[deleted]
pistachiopro 6y ago
Feels to me like: https://www.gdcvault.com/play/1026182/ https://www.gdcvault.com/play/1026182/ (which Nvidia has wrapped up in their RTXGI library: https://developer.nvidia.com/rtxgi https://developer.nvidia.com/rtxgi). The idea is to supplement basic irradiance probes with moment shadow maps, so you can efficiently calculate how much each pixel should be affected by each probe. This greatly reduces the light bleeding problem, which is the biggest downfall of irradiance probes. Nvidia uses raytracing to update some percentage of the probes each frame, and I wouldn't be surprised if UE5 does, too (despite the Euro Gamer article). That said, their geometry solution is likely more amenable to random access than traditional rasterization, so that may make raytracing for probes and probe shadow maps unnecessary. Also, judging by when the player character puts her hand on the door, it looks like there's a bit of screen space GI going on, as well.

by _bxg1 6y ago

I tried to figure out whether the new GI used raytracing, and it doesn't seem like it is? If it is using raytracing hardware it isn't nearly as impressive. If it isn't, then it's sheer magic.

skohan 6y ago

I'm almost certain they are. HW raytracing is of the big selling points of the new console generations, and if they achieved these kinds of results without it, then I would have to reconsider my skepticism of the occult.

paavohtl 6y ago
It was confirmed[1] in a Digital Foundry interview that the demo is NOT using HW raytracing. [1] https://www.eurogamer.net/articles/digitalfoundry-2020-this-is-next-gen-unreal-engine-running-on-playstation-5 https://www.eurogamer.net/articles/digitalfoundry-2020-this-...
- skohan 6y ago
  That's incredible. I look forward to learning more about how they do it
deleted 6y ago
[deleted]

olavgg 6y ago

Shadows are too sharp, so I don't think they use raytracing.

_bxg1 6y ago
It certainly isn't completely raytraced, because current hardware can't support that. If they use the new hardware, they're using it in some kind of mixed mode. Whether that means only for certain materials, or whether they're able to use it to do "fat rays" that approximate only the general direction for indirect light, or whatever else. But direct, hard shadows are quite cheap (comparatively) on today's regular, rasterization-based rendering systems, so that part isn't surprising.
- skohan 6y ago
  It certainly isn't fully path traced, but the result does look to me like they are using ray-traced GI. You can tell by some of the details, like colored bounce lighting which I am not sure can be achieved with this level of detail using other methods. The current standard for getting real-time performance for ray tracing is to limit the number of rays and bounces, and stabilize the results temporally. I.e. to get a "physically accurate" result you would have to send hundreds, or thousands of rays per pixel, and bounce them up dozens or hundreds of times. With this method, instead you send maybe even one or two rays per pixel, which gives you a noisy result. But you store the result, and accumulate it over a number of frames, and apply de-noising, and over time you end up with a high-quality result. I believe that is why when the light moves, the GI lags for a fraction of a second in this demo.
  - longtom 6y ago
    Another trick is in stead of tracing multiple bounces per ray at once, to compute one indirect bounce every n-th frame using intermediate results from the previous (not the current) frame and then spatio-temporally smooth the results, possibly with on-screen bilateral filtering of the past few frames. I think one can see they do this when they move the light source. It takes a while for the indirect bounces to fade out. Perhaps they use screen space ray tracing for this (meaning no indirect bounces for occluded geometry).
skohan 6y ago
Why would sharp shadows rule out raytracing? And how would they achieve this quality of GI without it?
- longtom 6y ago
  Because softer shadows add to the realism, so they would have used them if they had invented a new efficient ray tracing method! Look at 5:12 in the video. The shadows are way too sharp. It's probably good old shadow mapping for the first bounce and then screen space(?) global illumination.

deleted 6y ago

[deleted]

pistachiopro 6y ago

Feels to me like: https://www.gdcvault.com/play/1026182/ https://www.gdcvault.com/play/1026182/ (which Nvidia has wrapped up in their RTXGI library: https://developer.nvidia.com/rtxgi https://developer.nvidia.com/rtxgi). The idea is to supplement basic irradiance probes with moment shadow maps, so you can efficiently calculate how much each pixel should be affected by each probe. This greatly reduces the light bleeding problem, which is the biggest downfall of irradiance probes. Nvidia uses raytracing to update some percentage of the probes each frame, and I wouldn't be surprised if UE5 does, too (despite the Euro Gamer article). That said, their geometry solution is likely more amenable to random access than traditional rasterization, so that may make raytracing for probes and probe shadow maps unnecessary. Also, judging by when the player character puts her hand on the door, it looks like there's a bit of screen space GI going on, as well.