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Comment by jasonwatkinspdx | Hacker News Reader

While the above is accurrate I think it's a bit one sided.

Physically Based Rendering has become the dominant approach in VFX because it's a huge simplification and productivity boost. Integrating tons of special purpose hacks into one renderer isn't just hard for the renderer devs, the control parameters exposed to artists become an absolute nightmare. Combing the PBR perspective with raytracing greatly simplifies both sides of this.

Not every game is trying to be the next Far Cry. Ray tracing will be adopted by teams that value that unification and simplification over getting the very last bit of performance possible by a pile of hacks. As the hardware improves, which still seems likely, we'll see the balance point of who makes that call shift in favor of tracing IMO.

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I agree that PBR is awesome, but PBR doesn't slow things down, it is just a replacement by less accurate equations (BlinnPhong ambient,diffuse,specular) with better equations (GGX albeido, roughness, metallic, clearcoat, sheen) that are generally the same complexity.

It is sort of neutral on render time for the most part.

In time, I am sure we will be in a raytraced future if GPU trends continue.

Physically based rendering is _not_ the Disney shader and renaming your diffuse maps to albedo because it sounds more sciencey.

It’s about the wholesale switch to a fully path-traced framework with a consistent mathematical foundation as opposed to the layered system of hacks and chained prepasses that prevailed in the early 2000’s

This. You can use PBR concepts in an old school renderman style pipeline, but that's not why it's been a big deal in VFX. With a PBRT style renderer, everything is handled in a single monte carlo framework. And once you get an unbiased renderer that meets your standards, you can implement schemes like irradiance caching or photon mapping that introduce bias, but greatly accelerate rendering (and reduce noise). That optimization can be done once, for everything past and future.

That's why I'm saying the combination of PBR and tracing is a huge productivity boon to both sides, art and tech. It has a performance cost, but if/when hardware can pay that cost in real time, games absolutely will use it.

Worth adding that if we get more hardware support for deep neural networks on the GPU (e.g. tensor cores), training a denoising DNN on the noisy renders can save a lot of computation and fits neatly into the pipeline.

If the ray tracing can be done at or around 1 ray per pixel or less using a network trained to do merge information over multiple frames and upscale we could probably get away with less. Maybe more if we can feed in a depth map, velocity map and a flat shader less rendering or other information to help guide the DNN.

Might even end up faster than current raster renders.

See https://www.chaosgroup.com/blog/experiments-with-v-ray-next-...

With 4K around for corner for regular gamer screens, and top of the line GPUs that cannot handle that at an acceptable speed yet, I think it's a long time before we see that. Maybe when a 200$ GPU can do 4K 60 fps, but until then 5-10% gain is seen as worth chasing.

Every pass doesn't have to be rendered at native resolution, and most aren't. When you're running a game at 4K on your PS4 pro or modern PC, very often the 4K image is being produced using a mix of temporal anti-aliasing (accumulating a full image over time across multiple frames), heuristic upsampling, etc. Many post-processing passes run well below screen resolution even if you're running at 1080p - things like SSAO and even particle effects are typically rendered at a lower resolution.

Also, many modern games have been hitting 60fps at 4k on mid-high tier cards for years - you can hit 60 at 4k with reasonable quality settings in a game like MGS5 or GTA5 on a single 970. If you get a 1080 way more stuff runs great, even at higher settings.

Many modern games have an internal resolution slider as well, so you can set the internal resolution to 80 or 90% and still get your UI rendered at full 4K resolution. If the game has temporal anti-aliasing the difference tends to be hard to spot.

Finally, if you've got a freesync or gsync monitor, a few dips down to 50fps at 4k aren't going to be super noticeable, and the games look great. :)

>It has a performance cost, but if/when hardware can pay that cost in real time, games absolutely will use it.

Which has been said since earl6 2000. But the question is, when? Or if it will ever come?

If you look at road maps we surely dont have that in next 5 years, even unlikely in 10.

Actually PBR is quite a very important workflow innovation in rasterizing engines, see my post above!

That's not really what it's about! It's not about achieving physical correctness or ray tracing. You can have a PBR renderer selectively break energy conservation for artistic reasons. It's not about ray tracing either. Current game engines like Unreal and Unity are considered PBR because they use a roughness/metalness workflow.

PBR about having maps that are easy to understand through physical analogy, and simplifying the workflow so that it's mostly shared across render engines, applications and pipelines. It's about the ability to create texture in Mari or Substance, which use rasterizing engines, and seeing the final render in Arnold look nearly identical.

Non-3D artists should note that “Physically Based Rendering” or PBR is merely a standard for defining materials. It is becoming something of an industry standard in real-time and offline rendering workflows. From a real-time(games) perspective, PBR represents a leap up in realism but from an offline(VFX) perspective, it offers no improvement in realism, and often a downgrade from past norms if implemented with no additional efforts. For someone using offline rendering, [EDIT: As per pxl_fckr’s comment, I must be short on some history of PBR. I stand corrected.]

It actually means a lot more than that in offline VFX. It was the games industry that decided it meant “use the Disney shader”.

I updated my comment. I guess I need to read up on that. I read of so many areas in which PBR stops short in offline contexts, like using constant BRDFs which is a little unnecessary with offline rendering. What am I not understanding there?

I’m not quite sure of what you’re asking exactly here? What do you mean by constant brdfs?

I don't think pure raytracing and ray traced global illumination are going to be adopted by many games if there is still such a giant problem with noise. That is far from a solved problem, even in multi-hour per from visual effects renders.

This paper shows pretty good results from essentially throwing a RNN at it:

[1] http://research.nvidia.com/sites/default/files/publications/...

Where will the 1000 frame fly through and the 10 noisy frames that they use come from? I find that paper very disingenuous when they don't count these things in their filtering time.

Not only that, but they compare everything with "1 sample per pixel" knowing that the SURE filter uses per pixel statistics of variance that require more than one sample per to start working.

I guess with games there is already temporal anti-aliasing (TAA), so that would be an effective denoising technique if one was using noisy ray/path tracing.

That's definitely popular for effects that use ray casting. At SIGGRAPH and GDC over the past couple years, a good fraction of the graphics presentations I went to ended with "and then we added TAA because we could only afford a handful of samples per pixel per frame".

What do you mean by noise ? I know that Path tracing is incremental and producer a lot of noise at first but there is also other algorithme than part tracing. Also there is good denoiser filter that can be used with fragment shader.

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