How Metro Exodus uses Nvidia ray tracing to stunning effect
Nvidia showcased a number of ray tracing titles at its GeForce RTX launch and it was 4A Games' Metro Exodus - alongside DICE's Battlefield 5 - that impressed us most with its implementation of ray tracing technology. In fact, RTX on vs RTX off within the 4A title demonstrates the challenges and opportunities of the new hardware: right now, it seems we need to choose between remarkable realism and accuracy with a significant performance overhead, up against lighting based on established techniques - less accurate but still good-looking and much faster. Which will prevail?
First of all, it's important to remember that the RT cores within the Turing technology aren't powerful enough to provide a complete ray-traced rendering solution - processing power is finite, so the technology is effectively a new tool in the developer's toolbox and the end result is a hybrid combination of RT and standard rasterisation. DICE uses the RT cores for beautiful reflections, whereas 4A's approach is very, very different. Owing to its post-apocalyptic world, the major light sources are effectively just the sun and the moon, so the RT cores are put to work creating a diffuse global illumination implementation. In essence, ray tracing is a straight replacement for the game's standard lighting systems.
Light floods convincingly over the large open world terrain, producing some stunning scenes, but arguably the most noticeably complex light interactions occur within buildings, showcased effectively by 4A as shutters on windows rise, allowing light to flood into the room. In addition to this obvious 'wow' moment, ray tracing gives us remarkably accurate first bounce lighting, where the colour of certain objects can project onto other objects in the scene. And where there is light, there is also shadow, with the GI solution producing some remarkably effective ambient occlusion.
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