NVIDIA Shows Ada Lovelace’s Opacity Micro Maps Feature and How It Can Boost Ray Tracing Performance
When NVIDIA unveiled the Ada Lovelace architecture that GeForce RTX 40 Series GPUs are based on, we learned of a number of new features, such as DLSS 3, Shader Execution Reordering (SER), Displacement Micro Meshes (DMM), and Opacity Micro Maps (OMM).
DLSS 3 was, of course, the star since the very beginning. Its adoption rate is turning out to be much faster than DLSS 2, with 29 games already supported. SER is also slowly getting support in games, such as Sackboy: A Big Adventure and the upcoming Cyberpunk 2077: RT Overdrive Mode technology preview. The others, though, haven't been implemented by any third-party developer that we know of.
Between GDC and GTC, NVIDIA is trying to change that with dedicated showcases for these technologies. In this article, we're focusing specifically on Opacity Micro Maps, designed to speed up ray tracing performance whenever rays hit irregular objects.
In the Remixing “Portal” for RTX talk, NVIDIA's Distinguished DevTech Engineer Alexey Panteleev talked about the usage of Opacity Micro Maps in Portal RTX, which he found to be particularly useful given the number of particles and the empty spaces between them.
Opacity micro maps should help in cases like this one where there is a lot of particles on the scene and the particles have a lot of empty space on them.
The problem with empty space is that you have a single large billboard that contains that empty space, but it also contains non-empty areas, so whenever the ray tracing hardware in the GPU hits this billboard it doesn't know whether this hit is useful or not, so it will return the hit to the shader. and the shader must load the texture to determine if this hit is actually useful. If it's just empty space, the hit will be returned back
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