RTXDI can make any object in a game emit light and cast dynamic shadows, it's a technique that replaces all other shadow and ambient occlusion techniques. The technique works on all video cards that support DirectX or Vulkan ray tracing, so at least theoretically, AMD or Intel cards could support it too. A plug-in for Unreal Engine 4 is on the way.
NVIDIA promises RTXDI will remove the limit on the number of lights artists can use to author a real-time game environment. Allegedly, the performance cost between a couple of hundreds or several millions of light sources is very similar when using RTXDI:
RTX Direct Illumination promises to forego the so-called 'hero lights' phenomenon in games, where only a few select light sources were actually casting shadows. This will enable much more realistic scenes. But what about performance? Well, according to RTX UE4 Game Engine Evangelist Richard Cowgill, with RTXDI it shouldn't really matter if you need dozens, hundreds, thousands, or millions of lights; the cost is expected to be about the same. As a result, the performance should essentially flatten and be more consistent, particularly with NVIDIA DLSS enabled. -- WCCF TechHere are the main benefits, according to NVIDIA:
True Geometry For Lights
No more need for fake proxies. A more realistic simulation allows artists to create environments that approach photorealism. Lights with complex shapes, such as neon signs, work as they do in the real world.
Works as an Oracle for Shadow Rays
RTXDI tells the renderer where to send rays. Reducing the manual tuning required to light scenes will improve the efficiency of any art pipeline.
No More Hero Lights
Every light is a shadow caster. Scenes look richer and more grounded. Real-time renderings now reach the complexity level that only baked backgrounds previously allowed.
Built to be Paired with RTXGI
Can be combined with RTXGI for fast and scalable global illumination with many lights. RTXDI provides great results on its own, while amplifying the value of other NVIDIA ray tracing SDKs.
There is also a new RTX showcase demo, you can get it over here. This tech demo uses the Unreal Engine 4 and incorporates RTX Global Illumination (RTXGI), RTX Direct Illumination (RTXDI), NVIDIA Real-Time Denoiser (NRD), and NVIDIA DLSS.