2023 week 9: SL CCUG meeting summary – PBR

The following notes were taken from my audio recording and chat log transcript of the Content Creation User Group (CCUG) meeting held on Thursday, March 2nd, 2023 at 13:00 SLT. 

These meetings are for discussion of work related to content creation in Second Life, including current work, upcoming work, and requests or comments from the community, together with viewer development work. They are chaired by Vir Linden, and dates and times can be obtained from the SL Public Calendar.

Notes:

• These meetings are conducted in mixed voice and text chat. Participants can use either to make comments / ask or respond to comments, but note that you will need Voice to be enabled to hear responses and comments from the Linden reps and other using it. If you have issues with hearing or following the voice discussions, please inform the Lindens at the meeting.
• The following is a summary of the key topics discussed in the meeting, and is not intended to be a full transcript of all points raised.

Official Viewers Summary

The PBR Materials project viewer updated to version 7.0.0.578526, on March 3rd, 2023. Note that this viewer will only function on the following Aditi (beta grid) regions: Materials1; Materials Adult and Rumpus Room 1 through 4.

Available Viewers

• Release viewer: Maintenance Q(uality) viewer, version 6.6.9.577968 Thursday, February 2, 2023.
• Release channel cohorts (please see my notes on manually installing RC viewer versions if you wish to install any release candidate(s) yourself).
  • Maintenance R RC viewer, version 6.6.10.578285, February 28 – translation updates and the return of slam bits, together with the Group Chat History functionality.
  • Maintenance S RC viewer, version 6.6.10.578270, issued February 24 2023.
  • Performance Floater / Auto FPS RC viewer updated to version 6.6.10.578172, February 21, 2023.
• Project viewers:
  • Puppetry project viewer, version 6.6.8.576972, December 8, 2022.

General Viewer Notes

• The Maintenance R and the Performance Improvements / Auto-FPS RC viewers are both now apparently in line for promotion to de facto release status, although both may go through further RC updates prior to being promoted.

glTF Materials and Reflection Probes

Project Summary

• To provide support for PBR materials using the core glTF 2.0 specification Section 3.9 and using mikkTSpace tangents, including the ability to have PBR Materials assets which can be applied to surfaces and also traded / sold.
• To provide support for reflection probes and cubemap reflections.
• The overall goal is to provide as much support for the glTF 2.0 specification as possible.
• In the near-term, glTF materials assets are materials scenes that don’t have any nodes / geometry, they only have the materials array, and there is only one material in that array.
  • It is currently to early to state how this might change when glTF support is expanded to include entire objects.
• The project viewer is available via the Alternate Viewers page, but will only work on the following regions on Aditi (the Beta grid):  Materials1; Materials Adult and Rumpus Room 1 through 4.
• Please also see previous CCUG meeting summaries for further background on this project.

Status

• Work continues on viewer-side bug fixes.
• Tone mapping: work is progressing on implementing the Krzysztof Narkowicz variant of ACES tone mapping, which should – depending on the monitor being used  / viewer preferences set – produce better graphical results. As the result can vary by monitor / eye, this will include both an exposure slider and an option to disable the option.
• Geenz Linden is working on the Mac side of the PBR work; Comic Linden is finalising UV treatment  and Bed Linden is working on the one remaining server-side bug the team is aware of and Dave P (Runitai Linden) is working on atmospherics and issues with rendering them in linear space.
•  Linear space alpha blending: there are still issues with this, particularly at either end of the scale (high colours / high transparency and low colours / low transparency). This is being worked on, but may end up with a debug setting to disable linear space alpha blending by those who need to, with a warning that this is not how scenes are intended to be viewed.

In Brief

• It now looks as if the move away from the OpenGL API will be to Vulkan for Windows (/Linux?) and MoltenVK for Mac.
• LL is interested in implementing something similar to the Firestorm Local Mesh capability by Beq Janus and Vaalith Jinn (see here and here for more), possibly as a result of a code contribution.
• Land Impact:
  • Some creators are using the Animesh checkbox on upload to try to get around large mesh objects having heavy Land Impact values. LL gave notice at the meeting that this is regarded as an exploit, and it will be patched – so those doing so should really cease in order to avoid people facing unplanned object returns when their parcel start reporting they are over capacity.
  • In terms of Land Impact overall, it was acknowledged that while updated to allow for mesh, etc., the formula does still have some shortfalls; however, redressing this would require work which also involves bandwidth and server memory, and is not currently on the cards.
  • It is hoped that the move to support glTF mesh imports will offer a means to address LOD issues and Land Impact, as it will bring with it a fundamental shift in the data model
• Cull distance volumes: one way to reduce the render load on a system is to have cull distance volumes. The PBR reflection probes are being seen by LL as a means to test data gathering which can eventually be used in cull distance volumes (e.g. so you can set-up a volume inside a room and have it so that the viewer does not start rendering anything within that room until a camera is within X metres of the room).
  • This could potentially make Land Impact more dynamic in terms of content streaming costs, based on the use of cull volumes / camera position.
  • It could also be used to assist in privacy matters (e.g. “don’t render what’s in this room unless people are in this room”).

Next Meeting

• Thursday, March 16th, 2023.