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Intrinsic on 19 October 2014
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Vena said:


If you're bottlenecked by your CPU, it doesn't matter what the GPU can do especially if your rendering/lighting engine is CPU-bound. I'm calling bullshit on your calling bullshit. In order for Unity to be updated such that the GPU can be used to improve AC:U on the PS4 would likely require that the entire game's engine be re-written not only off of nVidia tech optimization but also specifically to utilize PS4 hardware, making the game have two seperate development chains... which was what developers were trying to get away from in this age of skyrocketting prices. (There's also doubt on whether or not the CPU-bound bottlenecks can even be circumvented by GPGPU as we have a lacking amount of details on the whole matter (GPGPU is not some sort of magic wand to suddenly offload CPU workloads) aside from an insider developer stating that getting this game even working as it is on these consoles with high fidelity graphics has been nothing short of a clusterfuck nightmare.) Moreover, if you unload an inefficient process for GPGPU from the CPU, you're robbing the game of the ability to spend its GPU power on other aspects of IQ; this is afterall a zero-sum game of power we're working with. For all we know, when Unity launches, the PS4 version may boast better texture details and other graphical qualities due to its higher GPU specs which would have had to have been sacrificed in the scenario where you unload a potentially ruinously ineffecient process from the CPU to GPGPU just so that you can reach 1080p.

I don't disagree with the rest of the statements as they are common sense facts, the PS4 has a stronger GPU and can do more things with said GPU and Ace (and lack thereof of esdram). Ya, Ubisoft is full of shit but they're not just crippling the game out of some twisted sense of satisfaction. There are deadlines, costs, and what not else that you and I are not privy to with our armchair development discussions.

Ok, forget about GPGPU for a moment. As far as ubisoft is concerned and according to them they are only using its for tech that deals with cloth (soft body) physics. They said this themselves, but this is not about ubisoft using GPU compute or not.

I have tried to explain how a render pipeline works. I would have gone ito the whole deferred and forward rendering but thats big enough to be a thread on its own. So let me put it simply.

  • You need to have the CPU + GPU complete their respective tasks in time for the next frame to go to the screen. You have a time allotment of 33ms.
  • The CPU starts first (frame 1) and does all its processing so it can feed the GPU with what the GPU needs to render the frame. Lets say it takes a hypothetical 20ms to finish its task.
  • Once finished, it hands over the instructions to the GPU. The CPUs work is done at this point and it immediately starts working on frame 2. 
  • The GPU still needs to render frame 1 and output it to the screen. It however now has exactly 13ms to do this so the entire first frame ends up taking 33ms; total 20ms CPU + 13ms GPU.
  • No matter how bound a game is to the CPU, at the point that the GPU is rendering frame 1 with the 13ms it has to do that its ALL on the GPU. Cause at this point the CPU is busy calculating frame 2. 
  • So basically, at this point both the XB1 and PS4's GPUs have got exactly 13ms to spit out a frame. 
Do you understand the problem now? 
  • Both consoles have approx the same time to render a frame. 13ms
  • The XB1 in that alloted time with its 12 core GPU manages to render and output a frame that is 900p.
  • How is it possible, that the PS4, with its 18 core GPU, still only manages to render the same 900p in the same amount of time?
  • Its taking the PS4s GPU the same time do the exact same amount of work even though the PS4s GPU is 50% more powerful than the XB1. don't you get it? If you read my part two of this series where I talk about the ESRAM I went into calculating the difference betwen 900p and 1080p. 1080p has ~40% more pixels than 900p. Thats typically where the extra power of the PS4 goes to. And whats funny is that by default, with minimal optimization... the PS4 will have that GPU based advantage every single time.
I never said that ubisoft set out to limit or restrict the PS4. I think I actually referred to the whole parity talk as nonsense. What simply happened here is that the XB1 was the lead platform. Ubi got the game running on in 900p@30fps. Ported the game game over to the PS4. Found out that the game wasn't as optimized for the PS4 because it was actually optimized for the other console. So rather than optimize here too, they just took the extra power the PS4 alread had and let the PS4 do all the work. For the PS4 to be running at 900p just means that the game is not optimized for it. And contrary to what you are saying, all devs are supposed to optimize for the respective hardware. And believe me when I say this gen its probably 95% easier optimizing from XB1 to PS4 than it was optimizing for 360 to PS3.