Friday, July 1

Unreal Engine 5 has a colossal asset to surprise us with such stunning graphics: Lumen, its global lighting engine

The ray tracing (ray tracing) has come into our lives to stay. When NVIDIA released the first graphics cards in the GeForce RTX 20 family in 2018 we were forced to moderate our expectations due to to the deep and negative impact that this demanding rendering technique has on performance. But since then three years have passed, and the landscape has changed. Much, and, above all, for the better.

Current GeForce RTX 30 graphics cards have managed to moderate the impact which has ray tracing in its overall performance, especially when combining this rendering technique with image reconstruction using DLSS 2.0. And NVIDIA is no longer alone on this path; AMD has also implemented support for ray tracing on its Radeon RX 6000 family graphics cards, although with a different philosophy than that used by NVIDIA.

The striking graphic finish of ‘The Matrix Awakens’ is largely due to how well Lumen solves global lighting dynamically.

In addition, the fact that PlayStation 5 and Xbox Series X and S incorporate a graphical logic entrenched on AMD’s RDNA 2 architecture also allows these video game consoles to put their own ray tracing on the table, contributing decisively to its popularization. This is, in short, the context in which the demo ‘The Matrix Awakens’ arrived a few days ago, a technical test that has left many game fans speechless due to its fantastic graphic quality.

This demo has been programmed using the Unreal Engine 5 graphics engine, which will undoubtedly be the one used by many new generation games in the future. And yes, it is spectacular. To a large extent its surprising graphic finish is due to how well this engine handles global lighting dynamically, a responsibility assumed by Lumen, its sophisticated lighting engine.

Thanks to him the images of this technical demo have in some moments shocking realism, so we suggest you investigate what is undoubtedly one of the star components of Unreal Engine 5.

Here’s how Lumen spends it to solve lighting and reflections so realistically

The description of this lighting engine What Epic Games offers us is quite a statement of intent: “Lumen is a completely new dynamic global lighting and reflections system built into Unreal Engine 5 and designed to new generation consoles».

The direct allusion to PlayStation 5, Xbox Series X and S responds to an obvious fact: your hardware is prepared to deal with the ray tracing, but they suffer more when using it than a PC equipped with a GeForce RTX 30 or a Radeon RX 6000 mid- or high-end range. Hence, this engine primarily seeks to help new consoles deal with ray tracing.

To solve global illumination and reflections in a realistic way, but at the same time, inflicting on the hardware stress as moderate as possible, Lumen uses several different ray tracing methods. The first thing it does is, roughly, analyze the scene to be rendered to identify the surfaces of the objects and store the parameters that define their characteristics in a buffer called Cache Surface.

Somehow this first operation allows the graphics engine get acquainted with global lighting required by that scene, paying special attention to the intersection points between each of the rays and the objects in the 3D scene.

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Right below Lumen identifies how it should reflect light each of the objects in the scene from several different angles and keeping in mind the material from which it is made. And then it calculates the direct and indirect lighting that must act on each of these surfaces.

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From that moment on it resorts to an algorithm known as Screen Space Tracing that, broadly speaking, calculate diffuse lighting of the scene and the direct lighting that affects the objects, but taking into account only the visible surfaces thanks to the information stored in the Z buffer or depth buffer. In this way, it is possible to significantly reduce the computational effort required by the graphics hardware.

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Lumen can tackle ray tracing in two different ways: by software and by hardware. The first option does not require hardware specifically dedicated to the ray tracing, so it works on a wide range of platforms. However, hardware ray tracing, as we can guess, requires the graphical logic to incorporate the functional units necessary to carry out this rendering procedure.

The execution of this lighting technique using software carries important limitations when it comes to the geometry of the objects in the scene and the material they are made of, so the best result will always be obtained using hardware ray tracing.

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The hardware ray tracing implemented in Lumen gives game developers a much wider range of geometries than the one that puts software rendering in your hands, so it will almost always offer us a more realistic visual finish. Of course, the stress it imposes on the hardware is considerable.

An interesting detail to conclude: in the images that illustrate this article we can see the credibility with which Lumen recreate the different materials used in each scene and the way they reflect light. In fact, some elements are almost indistinguishable from those that we can find in a photograph.

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More information | Epic Games

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