Rise of the Tomb Raider for the PC is the first title to officially use Nvidia’s VXAO (Voxel Ambient Occlusion) technology thanks to a spiffy new title update (which also added the touted DirectX 12 mode too). VXAO is considered by Nvidia to be the next evolutionary step of HBAO+, offering even higher quality and accuracy than the already established technology.
While we’re waiting for the slides for the GDC 2016 presentation (Advanced Ambient Occlusion Methods For Modern Gaming) to be placed online, Alexey Panteleev, Nvidia’s Senior Developer Technology Engineer at NVIDIA, also decided to write more about the technology on a blog post at Nvidia.
“It’s been awhile since we have announced VXGI, the real-time voxel global illumination technology. Since then, a lot of effort was put to productize it, integrate into Unreal Engine 4, and make it available for free. And it’s a great technology; it can produce realistic lighting with good occlusion for dynamic scenes with no preprocessing.” Alexey explains in his post.
“VXGI allows applications to compute multi-bounce indirect diffuse and specular lighting, use the cone tracing functions in application shaders for special needs like refractive materials or light map computation, and compute ambient occlusion effects based on voxel data.”
“In Rise of the Tomb Raider, not all locations benefit from VXAO equally well, and the reason for that lies in the game’s art and lighting solution. The game has separate channels for ambient lighting and ambient occlusion, and how exactly they are used is determined by materials. The ambient occlusion channel is often applied on top of direct lighting as well, and because VXAO is not a local effect and tends to add occlusion to large surfaces, some lights become dimmer.”
“So we had to apply VXAO to the ambient light channel instead and keep HBAO+ in the ambient occlusion channel in order to achieve the best look. It became clear that VXAO is mostly a long-range effect, and it’s useful to combine it with some short-range SSAO technique to highlight small features which cannot be adequately represented by voxels. For this reason, VXAO now includes an optional screen-space occlusion pass so that you don’t have to work with a separate SSAO library.”
While the usage of VXAO (Voxel Ambient Occlusion) does require a good amount of GPU performance to process, it’s more efficient in memory compared to VXGI. VXGI can be between 500MB to a staggering 7GB for a rendered scene,VXAO meanwhile is between 6MB and 100MB.
Fortunately, VXAO is being developed to easily be implemented into Unreal Engine 4. As usual, we’ll continue to cover this exciting technology here at RedGamingTech.