Unreal Engine 4 was presented at the PlayStation 4 announcement conference through a new Elemental Demo. We noted how the quality seemed to have dropped in the eight months following E3 while the demo was being ported to the console hardware. The most noticeable differences were in the severely reduced particle counts and the non-existent fine lighting details; of course, Epic pumped the contrast in the PS4 version which masked the lack of complexity as if it were a stylistic choice.
Still, the demo was clearly weakened. The immediate reaction was to assume that Epic Games simply did not have enough time to optimize the demo for the hardware. That is true to some extent, but there are theoretical limits on how much performance you can push out of hardware at 100% perfect utilization.
Now that we know both the PS4 and, recently, the Xbox One: it is time to dissect more carefully.
A recent LinkedIn post from EA Executive VP and CTO, Rajat Taneja, claims that the Xbox One and PS4 are a generation ahead of highest-end PC on the market. While there are many ways to interpret that statement, in terms of raw performance that statement is not valid.
As of our current knowledge, the PlayStation 4 contains an eight core AMD "Jaguar" CPU with an AMD GPU containing 18 GCN compute units, consisting of a total of 1152 shader units. Without knowing driving frequencies, this chip should be slightly faster than the Xbox One's 768 shader units within 12 GCN compute units. The PS4 claims their system has a total theoretical 2 teraFLOPs of performance and the Xbox One would almost definitely be slightly behind that.
Back in 2011, the Samaritan Demo was created by Epic Games to persuade console manufacturers. This demo was how Epic considered the next generation of consoles to perform. They said, back in 2011, that this demo would theoretically require 2.5 teraFLOPs of performance for 30FPS at true 1080p; ultimately their demo ran on the PC with a single GTX 680, approximately 3.09 teraFLOPs.
This required performance, (again) approximately 2.5 teraFLOPs, is higher than what is theoretically possible for the consoles, which is less than 2 teraFLOPs. The PC may have more overhead than consoles, but the PS4 and Xbox One would be too slow even with zero overhead.
Now, of course, this does not account for reducing quality where it will be the least noticeable and other cheats. Developers are able to reduce particle counts and texture resolutions in barely-noticeable places; they are also able to render below 1080p or even below 720p, as was the norm for our current console generation, to save performance for more important things. Perhaps developers might even use different algorithms which achieve the same, or better, quality for less computation at the expense of more sensitivity to RAM, bandwidth, or what-have-you.
But, in the end, Epic Games did not get the ~2.5 teraFLOPs they originally hoped for when they created the Samaritan Demo. This likely explains, at least in part, why the Elemental Demo looked a little sad at Sony's press conference: it was a little FLOP.
Update, 5/24/2013: Mark Rein of Epic Games responds to the statement made by Rajat Taneja of EA. While we do not know his opinion on consoles… we know his opinion on EA's opinion: