Quixel Libraries are already used for a large majority of games today.
It's a fantastic resource (albeit quite expensive) of very high quality digital images converted for usage as HDR Physically Based Material Sources.
And sure, when you don't have those pesky limitations such-as Mainstream Video Memory (2-4GB) to worry about., you can produce some exceptionally High Fidelity Results, that are arguably very close to Cinematic Quality.
At least in terms of Environments.
But notice the lack of life within the scenes... no Animals, no People, etc.
Beautiful but Dead Environments.
Look Modern Hardware, especially High-End have quite substantial Video Memory and are capable of pushing somewhat insane Triangle Counts / Frame.
If we just take something Low-End., such-as the Ryzen 5 2400G with Vega 8... that's capable of ~80M Tris/Frame., provided we're talking about Static (basic Transform & Shaded) with PBR actually being quite a Lightweight Compute Shading Solution on Asynchronous Hardware (as we're sharing a lot of the resources, which really cuts down on the expensive calls such-as Depth Buffers or alike).
As such, this means we can get away with 1.26M Triangles / Scene at 60Hz., now you combine that with the ability to throughput ~320M Pixel / Scene (at 60Hz) … well this allows for some exceptionally High-Quality Image Output., provided a lot of what we're doing is "Static" … more so if we're not talking about a lot of Overdraw.
Just because these are no longer Modern Metrics that GPU Manufacturer' List, nor do Tech Media even seem to care about measuring such... doesn't mean that suddenly such things became unimportant. It's just typically speaking the Compute and Threading started to become a more important metric to determine general performance capabilities.
i.e. Jungle Scenes have a lot of Flora, that requires a lot of Overdraw due to Transparency / Alpha., this essentially doubles *per Layer* of Overdraw the Performance Cost... this is oft improved in Modern Engines with various Transparency Order Calculators to perform more simplistic Accept & Discard approach that reduces the Overdraw Count., but still if you want "Realism" you somewhat MUST omit such approaches.
Still again notice how none of the scenes have a lot of Flora present... instead it's all Dead, Desolate and Industrial.
This isn't to say that the "Real-Time" Machinima isn't visually appealing., but rather that people will oft leap to the notion that "This is something we could see in Real-Time Applications., such-as Games" in the near future is oft misguided.
I mean look., there are areas of Battlefront (as DICE heavily use Quixel Resources) that look Photorealistic., something you can capture in Screenshots and be like "Look at what can be achieved" … and sure, it's impressive., but anyone who has actually played Battlefront / Battlefront 2 knows full well... it doesn't ALWAYS look like those Screenshots.
When we're talking about a Pre-Rendered / Pre-Scripted effort., well you can fully control things so that any 'problematic' areas that break the illusion of the quality can be reduced... you're creating the Scene specifically for the intended Framing., the same is true for Movies in General... there's a lot of careful editing that goes into them (well normally speaking) to make them look as seamless and believable as possible.
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In some ways, I think this is partially why Tech Demos for each new Generation of GPU (AMD/NVIDIA) stopped being produced.
Not because new Features weren't being added that could dramatically improve what was possible with advancements, but because there was a false expectation of what the Hardware could realistically accomplish in actual Real-Time Scenarios Vs. the Tailor Made Tech Demo.
Don't get me wrong., I would highly recommend a Subscription to Quixel should you be interested in creating Realistic Environments for your Game(s).
It's an exceptional library that is professionally sourced, and edited taking A LOT of work out of getting High-Quality Texture Sources, which then can be used in Material creation with things such-as Marmoset or Substance Materials.
And I think it would be a good idea to suggest to TGC that they support either/or both Marmoset and Substance Material System (heck I'd even suggest they support Autodesk' Shader FX System) because these are industry standards.
I'm just saying, don't read too deeply into individual Technical Demonstration Pieces / Projects., especially those done by Art Students as part of their Long-Term Projects / Demo Reels... as there's a bit more work that goes into producing something of such High Visual Quality than simply using the same Resource Libraries., and such projects can be exceptionally time consuming too.
That's not always the best utilisation of Development Time.