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Rendering time of the Unreal Engine 5 demo geometry was not superior …

by ace

Basically Epic puts it in a different light. That the reduction of polygons achieved by the engine does not put more pressure on the GPU than a current generation game.

EPIC came again to talk about its Unreal Engine, and this time in a very interesting perspective. Basically EPIC implies that when it comes to the time dedicated to processing the geometry of the impressive demo it showed us, it is not superior to what the current generation consoles dedicate to their games.

This in a clear reference that the demo is not about Tflops or gross performance, but about the capabilities of I / O, data streaming, and removing excess polygons. And in that sense, it is no wonder that EPIC chose PS5 for its demo, considering it “a masterpiece in system design”.

Now when it is said that the rendering time was low, and just like the current consoles, the question may arise. If so, why wasn’t the demo at 4K, 60 fps?

Well, because in reality EPIC only addresses part of what is accomplished. But not all the work done by the GPU for that scene.

If you remember the demo of Unreal Engine 5, it presents us with a scene where there are only 16.5 billion polygons on statues on the screen. This does not even consider the rest of the ultra-detailed geometry of the entire dome and additional works of art.

Perhaps not everyone is aware of this, but this number of polygons is something that no home system can manage in real time … let alone 30 fps per second. In fact, it is so surreal that an RDNA GPU cannot generate as many polygons, let alone move them all at 30 fps.

If we read the white papers from the RDNA, we realize that this architecture has 4 shader arrays, each one including a primitive unit. This situation allows a total of 4 polygons to be generated for each clock cycle. This means that we can extrapolate this to the PS5 maximum polygon generation limit, which is the larger of the two new generation consoles, and which will be:

4 * 2230 = 8.92 billion triangles per second.

This is a situation that depends only on the clock speed and as such, being the PS5 the console with the highest speeds, it is the one that offers the highest throughput of triangles.

In other words, we have a total of polygons on the screen, moved at 30 frames per second, which is more than double what the console can generate in a second. Believe that what is shown there is a colossus, something unthinkable to see today, and that it is achieved thanks to the speed of the PS5’s SSD and its ability to read data directly into RAM and GPU caches thanks to the innovative console I / O system. It is the reason for the compliments to the console. To be able to overcome something that until today was a barrier in the hardware.

But the question that arises is … How does the console manage to move more than 16.5 billion triangles? And at 30 fps?

In reality it can’t … No home system can. This is where the geometry engine and its “culling” capabilities, or removal of invisible triangles, come in.

According to EPIC, PS5 in that demo they are managing to reduce the more than 16.5 million triangles to 20 million. Everything else is not visible!

But why 20 million? Well, in theory it was possible to reduce these triangles to something in the order of 8.3 million, without any loss of quality, since 8.3 million is the number of pixels we have on the 4K screen. And when we have triangles the size of pixels, we gain nothing in reducing them.

But, as a rule, it is common to work with safety margins. Situations that allow an unexpected movement does not expose the lack of polygons in any area. And in this respect, EPIC says it works with values ​​between 8.3 and 20 million polygons, depending on the scene.

Now 20 million triangles is what the most advanced games today calculate in their most complex scenes. Fortnite, the example given, is not even one of those that pulls more polygons, but as it pulls at 60 fps and not at 30 fps, that number doubles! This means that Fortnite ends up processing an average similar to the same number of polygons as the UE 5 demo per second.

It is an impressive figure. Which shows that with complex geometry, but without going into the crazy 16.5 billion, PS5 can deliver impressive results. And who knows, let’s all wait … Xbox too!

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