It’s been over six years since the first consumer-level graphics cards arrived that supported hardware accelerated ray tracing and while hardware has improved massively since the launch of Nvidia’s Turing architecture in 2018, this has been matched with innovations in the software space. RTX Mega Geometry was revealed at CES 2025 with a range of compelling demos, but now we have our first example of the technology in a shipping game: Alan Wake 2. There are quality, efficiency and performance upgrades but perhaps the biggest surprise in our testing is that it’s the RTX 20-series and 30-series GPUs that benefit most.
Let’s start with the basics – what is RTX Mega Geometry? This requires an understanding of how RT actually works. As things stand, every game essentially creates two 3D worlds – the world as you see it in-game and a secondary ‘BVH structure’ which is typically a lower detail rendition of the environment. BVH stands for bounding volume hierarchy. Rays are projected into the BVH structure and their direction is then calculated. As you might imagine, RT itself is already computationally expensive, so creating and tracing into the BVH structure adds to the cost. Furthermore, there are limitations – while the game world may be animated, it does not mean the BVH will be, potentially leading to mismatches and loss of visual quality.
Enter RTX Mega Geometry, which is basically a new API allowing for a new type and hierarchy to the BVH structure, containing the game world’s geometry and assets. The focus is on animated geometry, support for a larger amount of level-of-detail transitions and adaptive tesselation where the amount of actual geometry per frame is constantly changing. Mega Geometry adds a new level to the BVH structure: the CLAS or Cluster Acceleration Structure. While the extra complexity adds to the time to trace rays, there’s an extraordinary increase in detail and support for animated environments.
RTX Mega Geometry is essentially an Nvidia-branded version of a fundamental change to RT APIs that will almost certainly be adopted by all vendors. In a world where mesh shading, Epic’s Nanite and the basic requirement for animated environments come to the fore, the existing DXR APIs aren’t really fit for purpose – all of which brings us to the specific implementation found in Remedy’s Alan Wake 2.