RTX Direct Illumination (RTXDI)
Imagine adding millions of dynamic lights to your game environments without worrying about performance or resource constraints. Tiny LEDs. Times Square billboards. Even exploding fireballs. NVIDIA RTX™ Direct Illumination (RTXDI) makes this possible while rendering in real time and easily incorporates lighting from user-generated models. Geometry of any shape can emit light, cast appropriate shadows, and move freely and dynamically.
RTXDI Product Benefits
True Geometry for Lights
With RTXDI, there’s 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 improves 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
RTXDI 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.
RTXDI Off and On Comparison
RTXDI Off
- You can ray trace area light shadows for only a limited number of lights, even with the most powerful GPUs on the market.
- Typically only 2-16 of the “most important” lights in AAA RTX titles—and up to 100 lights in Quake 2 RTX and Minecraft RTX—can be ray traced.
RTXDI On
- With RTX on, you can ray trace up to millions of dynamic lights in real time.
- Lights are made of “true geometry.” Any object in a game can emit light and cast dynamic shadows, enabling an entirely new class of content.
- There’s only one shadowing algorithm: RTXDI replaces all other shadow and ambient occlusion techniques.
Comparing RTXDI to Other State-of-the-Art Techniques
Photo courtesy of artist GoldSmooth & TurboSquid
The image on the left uses prior state-of-the-art sampling techniques. The image on the right uses RTXDI, which can generate a beautiful finished image with the same level of overhead. Both images were constructed in equal time, using an equal number of rays per pixel.
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FAQ
A: RTXDI is a software development kit that leverages the power of GPU ray tracing in real time to provide a scalable solution for the computation of direct illumination and shadows for scenes involving millions of light sources.
A: Yes! The ability to trace arbitrary rays is critical for rendering scenes with shadows from millions of lights without the use of shadow maps.
A: RTXDI supports thousands to millions of dynamic area light sources in real time without requiring a high-maintenance data structure or offline preprocessing. Support for millions of area lights means that any mesh can be broken down into triangles, and each triangle can emit light into the scene. Such mesh would cast realistic lighting and shadows onto the objects around it, including self-illumination and self-shadowing if some parts of the mesh are not emissive.
A: RTXDI supports mesh lights as well as regular “primitive” lights, such as spheres, spot lights, and rectangular lights, as well as "infinite" lights, such as environment maps and directional lights like the sun. Mesh lights are just any objects in the scene that have an emissive component in their material that can be evaluated before rendering the scene. So, artists don’t need to do anything extra to light their scenes with mesh lights (depending on the RTXDI implementation in a particular engine).
A: The RTXDI SDK is a full-source distribution. The SDK includes the complete C++ and HLSL source code of the SDK, as well as documentation for the SDK code. A full-source sample application that demonstrates how to use the SDK is also included.
A: The RTXDI SDK supports DirectX Raytracing (DXR) API versions 1.0 and 1.1 for DirectX12 , as well as Vulkan Ray Tracing via the VK_KHR_ray_query and VK_KHR_ray_tracing_pipeline APIs on Windows.
A: RTXDI works on any GPU with support for the DirectX Raytracing or Vulkan Ray Tracing, including all NVIDIA RTX 30 series and RTX 20 series GPUs.
A: RTXDI will be made available as part of the NvRTX UE 4.26 branch. No current plans regarding Unity.