Emir_de_Passy
Active member
Please consider implementing Quad View Foveated rendering in LMU as it would be beneficial for ALL VR HEADSETS. (Not just eye tracked or expensive ones).
For those who are unfamiliar, it is a form of Foveated rendering that involves two small high-resolution focus areas and two low-resolution peripheral areas, with the focus areas in the center, where the gamer is looking directly.
It is the same principle as the foveated rendering we have been using with the OXR toolkit or VRperfkit, except it reduces pixel count while the variable shading rate (VRS) method used in OXR toolkit and VRperfkit adjusts the level of detail within a pixel block without changing the overall pixel count, which is why QVFR is significantly more powerful. People sometimes believe that it's exclusive to eye-tracked headsets, but it's beneficial for all types. The only difference is that, with an eye-tracked headset, you can make the focus areas smaller. QVFR is more CPU intensive (4 views to render instead of 2) but saves a lot of GPU workload. For example, Pimax could go from 5 to 55fps using DCS with a Crystal and an RTX 2060. According to the modder who implemented it in Richard Burns Rally, it was easy,
Here is a link that explains more; hopefully, you can determine if it is easy to implement in LMU.
https://github.com/mbucchia/Quad-Views-Foveated/wiki
- Foveated rendering is great for performance
- VRS is easy and cheap on the CPU
- QVFR involves doing a second render pass for the foveated part at a higher resolution then merging, which is a cpu cost, but greatly reduces GPU load
- both the above techniques work with both Fixed Foveated rendering and eye-tracked foveated rendering.
- On the headsets that support it, eye-tracked foveated rendering is a great way to go
A second render pass for the foveated part' is the same high-level thing that's done with XR_VARJO_quad_views but in no way requires it. If this is done in the engine, it works everywhere, it can be always on, and because it works everywhere and is always on, doesn't increase the amount of different configurations that needs to be tested.
If you want to do the composition yourself, here is a link: https://registry.khronos.org/OpenXR/specs/1.0/html/xrspec.html#XR_EXT_eye_gaze_interaction
This also makes it work on every headset without an API layer, but is more involved than what the RBR dev did.
Quad view foveated rendering is also available as an extension in OpenXR 1.1 (under the name Stereo with Foveated Rendering) https://www.khronos.org/news/press/...ther-streamline-cross-platform-xr-development
Another way to implement would be to support quad views in an API layer as the RBR modder did.
This would be easier than doing the composition yourself but this would only make it work with the list of headsets below (already quite extensive). This also requires an API layer whereas the first option doesn't.
github.com
Quad view foveated rendering in LMU would make it the de facto best VR sim racing implementation by a significant margin. It would guarantee to attract new VR users, many of whom use other titles mostly because they run well in VR. (e.g. AMS2, Iracing). QVFR would make LMU easier to run in VR than on triple screens and even on Ultrawide screens and, therefore, accessible to people with more modest PC configurations.
Here is a link to a discussion about various possible implementations:
www.reddit.com/r/Pimax/comments/1gisyv8/comment/lvdy3o2/
P.S. Apologies if I wrote any inaccuracies, as I am not a specialist.
UPDATE APRIL 2025: Microsoft Flight Simulator 2024 now supports QVFR and is the first current sim to do so not by accident. (Richard Burns Rally supports QVFR but is done by a modder)
Their implementation works on every headset without the need for any mod or special headset software, just like I wrote it could be done above. The GPU performance gain is about 30% and hopefully will improve when out of beta status. This is done at the cost of CPU performance, as expected.
Here is a technical summary of how they did it, from Mbucchia, the QVFR God.
forums.flightsimulator.com
UPDATE MAY 2025: IRACING now supports QVFR with their Season 3 2025 update. And is the second current sim to do so not by accident. The method used is a 2018 Nvidia API called Multi View Rendering which expands on Single Pass Stereo, which was already implemented. It's extremely effective and has a small CPU cost. However it only works with nvidia GPU.
developer.nvidia.com
For those who are unfamiliar, it is a form of Foveated rendering that involves two small high-resolution focus areas and two low-resolution peripheral areas, with the focus areas in the center, where the gamer is looking directly.
It is the same principle as the foveated rendering we have been using with the OXR toolkit or VRperfkit, except it reduces pixel count while the variable shading rate (VRS) method used in OXR toolkit and VRperfkit adjusts the level of detail within a pixel block without changing the overall pixel count, which is why QVFR is significantly more powerful. People sometimes believe that it's exclusive to eye-tracked headsets, but it's beneficial for all types. The only difference is that, with an eye-tracked headset, you can make the focus areas smaller. QVFR is more CPU intensive (4 views to render instead of 2) but saves a lot of GPU workload. For example, Pimax could go from 5 to 55fps using DCS with a Crystal and an RTX 2060. According to the modder who implemented it in Richard Burns Rally, it was easy,
Here is a link that explains more; hopefully, you can determine if it is easy to implement in LMU.
https://github.com/mbucchia/Quad-Views-Foveated/wiki
- Foveated rendering is great for performance
- VRS is easy and cheap on the CPU
- QVFR involves doing a second render pass for the foveated part at a higher resolution then merging, which is a cpu cost, but greatly reduces GPU load
- both the above techniques work with both Fixed Foveated rendering and eye-tracked foveated rendering.
- On the headsets that support it, eye-tracked foveated rendering is a great way to go
A second render pass for the foveated part' is the same high-level thing that's done with XR_VARJO_quad_views but in no way requires it. If this is done in the engine, it works everywhere, it can be always on, and because it works everywhere and is always on, doesn't increase the amount of different configurations that needs to be tested.
If you want to do the composition yourself, here is a link: https://registry.khronos.org/OpenXR/specs/1.0/html/xrspec.html#XR_EXT_eye_gaze_interaction
This also makes it work on every headset without an API layer, but is more involved than what the RBR dev did.
Quad view foveated rendering is also available as an extension in OpenXR 1.1 (under the name Stereo with Foveated Rendering) https://www.khronos.org/news/press/...ther-streamline-cross-platform-xr-development
Another way to implement would be to support quad views in an API layer as the RBR modder did.
This would be easier than doing the composition yourself but this would only make it work with the list of headsets below (already quite extensive). This also requires an API layer whereas the first option doesn't.
What is Quad Views rendering?
An OpenXR API layer to emulate quad views and foveated rendering support on many headsets. - mbucchia/Quad-Views-Foveated
github.com
Quad view foveated rendering in LMU would make it the de facto best VR sim racing implementation by a significant margin. It would guarantee to attract new VR users, many of whom use other titles mostly because they run well in VR. (e.g. AMS2, Iracing). QVFR would make LMU easier to run in VR than on triple screens and even on Ultrawide screens and, therefore, accessible to people with more modest PC configurations.
Here is a link to a discussion about various possible implementations:
www.reddit.com/r/Pimax/comments/1gisyv8/comment/lvdy3o2/
P.S. Apologies if I wrote any inaccuracies, as I am not a specialist.
UPDATE APRIL 2025: Microsoft Flight Simulator 2024 now supports QVFR and is the first current sim to do so not by accident. (Richard Burns Rally supports QVFR but is done by a modder)
Their implementation works on every headset without the need for any mod or special headset software, just like I wrote it could be done above. The GPU performance gain is about 30% and hopefully will improve when out of beta status. This is done at the cost of CPU performance, as expected.
Here is a technical summary of how they did it, from Mbucchia, the QVFR God.
Quad Views Foveated Rendering for MSFS 2024
I spent a little bit of time using the PIX graphics debugger to try to explain how the quad views rendering works in SU2. (While I’m not allowed to talk about some of the details I discussed with the devs, I consider my findings with the PIX debugger “publicly available”, since anyone with the...
forums.flightsimulator.com
UPDATE MAY 2025: IRACING now supports QVFR with their Season 3 2025 update. And is the second current sim to do so not by accident. The method used is a 2018 Nvidia API called Multi View Rendering which expands on Single Pass Stereo, which was already implemented. It's extremely effective and has a small CPU cost. However it only works with nvidia GPU.
iRacing Development Update: May 2025 - iRacing.com
Hello iRacers, The past few months have been busy in motorsports (both real-world and simulated), and time has flown by since we last provided our quarterly update. Between intense early-season championship battles across many of the world’s top-tier racing series and record-smashing...
www.iracing.com
VRWorks - Multi-View Rendering (MVR)
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