VXAO Explained - Highest Quality AO, Available on All DX11 GPUs; Supports DX12 and OpenGL 4.5, Too

VXAO Explained – Highest Quality AO, Bachelor on All DX11 GPUs; Supports DX12 and OpenGL 4.5, Too

VXAO (Voxel Ambient Occlusion) was announced ahead of Rise of the Tomb Raider'south launch and so added in a recent update, alongside back up for DirectX 12. It's function of the GameWorks iii.1 update, along Volumetric Lighting and HFTS (Hyper Frustrum Traced Shadows).

This is the get-go real world awarding for VXAO, which NVIDIA considers the "next stride in ambient occlusion engineering science" beyond HBAO+. Alexey Panteleev, Senior Developer Technology Engineer at NVIDIA, was the pb engineer on VXGI (Voxel Global Illumination) and he also presented VXAO (which is derived from VXGI) during hisAvant-garde Ambient Apoplexy Methods for Modernistic Games GDC 2022 presentation.

Unfortunately the slides oasis't been published nonetheless, only Panteleev divulged lots of data in a blog mail on the official NVIDIA developer website.

He began by reiterating how VXAO was designed.

One of these features has been left with too picayune attention: the ambience occlusion mode, or VXAO as nosotros call information technology. The idea is uncomplicated - we remove the lighting part [from VXGI] and continue only the occlusion part. Obviously, it is much less resources intensive: computing VXAO for a frame can be 2-10x faster than calculating full global illumination solution, depending on settings. At the same time, VXAO is three-4x slower than HBAO+, while its results are much better than HBAO+.

If you lot accept worked with screen-infinite ambient apoplexy algorithms, you know the master issues that they come up with. These are:

• Dark halos or lack of occlusion backside foreground objects;
• Unstable results most screen borders;
• Locality, which means that only a small book around a surface contributes to AO;
• Blurriness, which comes from a blur filter required because calculating a complete solution for every pixel would be too expensive.

VXAO has none of these issues considering it is based on a unlike principle. Instead of relying on screen infinite information, it gathers data from a earth space voxel representation of the scene, which covers a large area effectually the viewer. It doesn't thing if some object is not visible to the viewer - it can exist behind something else, or even behind the viewer - information technology's nevertheless in that location, and it still contributes to ambient occlusion. VXAO uses voxel cone tracing, so objects that are relatively far from the surface under consideration tin can nevertheless contribute, and taking them into business relationship is not equally expensive as it would be in a screen space algorithm.

Let'south take a await at this epitome comparing.

As highlighted past Panteleev, the obvious differences can be mainly found in the following places:

• Ground under the tank: no occlusion from HBAO+, some occlusion from VXAO.
• Lesser role of the tank tracks: no occlusion from HBAO+, meaning occlusion from VXAO.
• Metal stand up on the left side: a lot of occlusion from HBAO+, well-nigh none from VXAO.
• Barrel backside the fire hydrant: halo around the hydrant from HBAO+, no halo from VXAO.

According to him, this new Ambient Occlusion engineering science handles dynamic scenes quite well.

Nigh of the voxel data can exist preserved between frames, unless at that place are lots of moving objects or the camera moves quickly. And even if no voxel data can be preserved, voxelizing geometry again is non too expensive. Voxelization of a typical, loftier-particular game scene with a few one thousand thousand triangles tin be washed in about three-5 milliseconds on a modern GPU like GeForce GTX 980.

Overall, in that location are three major passes in the VXAO algorithm: voxelization, voxel post-processing, and cone tracing. Voxelization is performed by rendering the triangle meshes into a 3D texture, and as such, its functioning highly depends on the total number of triangles, size of these triangles, and the number of draw calls required to return them. Postal service-processing combines passes like clearing, filtering and downsampling voxels, and its functioning depends on the total number of voxels produced during voxelization. Typical mail-processing fourth dimension is 0.five – 1.v ms. And finally, cone tracing is performed in screen infinite, so its functioning depends on the screen resolution, shading rate, and the cone tracing pass in 1080p resolution.

Developers tin rest piece of cake in terms of memory management besides. The requirements are much lower than VXGI, which tin can get anywhere from 500MB to 7GB with the highest settings, while VXAO is generally between 6 to 100MB. Panteleev then proceeded to clarify that both VXGI and VXAO are far from exclusive to Maxwell or even NVIDIA GPUs.

Finally, if you saw the original announcement of VXGI at Maxwell launch, y'all may retrieve it works only on Maxwell. That'south not true. Maxwell does have some useful hardware features, simply the merely 1 relevant to VXAO is pass-through geometry shaders, which improve voxelization performance by approximately xxx%, and they can be safely replaced with regular geometry shaders. So VXGI in general and VXAO in particular can piece of work on all DX11 course GPUs, including ones made past NVIDIA competitors, but Maxwell GPUs deliver the best performance. It'south non limited to DX11 either: DX12 and OpenGL 4.5 are besides supported.

Going back to Rise of the Tomb Raider, the first implementation in an actual game of this technique, Panteleev explained that the particular fine art and lighting solution employed in this title doesn't allow VXAO to smoothen in all situations every bit.

The game has separate channels for ambient lighting and ambience occlusion, and how exactly they are used is determined past materials. The ambient occlusion channel is often applied on top of straight lighting as well, and because VXAO is not a local effect and tends to add together occlusion to large surfaces, some lights go dimmer. And so nosotros had to utilize VXAO to the ambient light channel instead and keep HBAO+ in the ambient occlusion channel in guild to achieve the best look. It became clear that VXAO is mostly a long-range result, and it'southward useful to combine it with some brusk-range SSAO technique to highlight small features which cannot be adequately represented by voxels. For this reason, VXAO now includes an optional screen-infinite occlusion pass so that you don't take to work with a separate SSAO library.

VXAO can exist easily enabled by those developers using Unreal Engine iv. In that case, you simply need to set the console variable "r.VXGI.AmbientOcclusionMode" to 1 and enable VXGI Diffuse Tracing in Post-Process Volume settings. If you're using whatsoever other engine yous'll have to integrate VXAO into information technology, though Panteleev promises that the process is not too complicated.

The distribution packet, alongside the samples and an integration tutorial, tin be found here.

Source: https://wccftech.com/vxao-explained-highest-quality-ao-dx11-gpus-supports-dx12-opengl-45/

Posted by: kimafor1996.blogspot.com

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