2023 week 7: SL CCUG and TPVD meeting summaries: Mirrors!

Under the Northern Lights, December 2022 – blog post

The following notes were taken from:

  • My audio recording and chat log transcript of the Content Creation User Group (CCUG) meeting held on Thursday, February 16th 2023 at 13:00 SLT.
  • My chat transcript and the video recording of the Friday, February 17th TPV Developer’s meeting, recorded by Pantera Północy and embedded at the end of this article. My thanks, as always, to her for recording these meetings.

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.


  • 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

Available Viewers

The have been no further updates to the currently available official viewers sine the PBR materials viewer was updated at the start of the week, as reported in my week #7 SUG meeting summary. Therefore the pipelines remain as follows:

  • Release viewer: Maintenance Q(uality) viewer, version 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).
  • Project viewers:
    • PBR Materials project viewer, version, February 14, 2023. This viewer will only function on the following Aditi (beta grid) regions: Materials1; Materials Adult and Rumpus Room 1 through 4.
    • Puppetry project viewer, version, December 8, 2022.

General Viewer Notes

  • It is hoped that the Performance Floater RC viewer will be promoted to de facto release status within the week, which would allow all official viewers to leverage Visual Studio 2022 on Windows builds going forward.
  • There are some changes to be made to github due to all the pull requests (PRs) going to branches which can change over time, causing issues as they do so. In the future, it is likely that PRs will go into the Main branch (which only changes on a per release basis) and from their moved into their intended branch.

CCUG – 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.


  • Viewer:
    • Work continues on bug fixes.
    • A major new bug is the discovery that the UV treatment is off-specification. This appears to be due to OpenGL putting the 0,0 coordinate in the lower left corner of the image rather than the top left. This does mean that all PBR materials uploaded to Aditi (the beta grid) prior to the fix going into the viewer will effectively be “broken” post-fix. Viewer:
    • The lighting model for water in the project viewer has been updated to use the glTF specification lighting model for water so that reflection probes can be used to generate reflections on water. However, trying to adapt the “old” water shader to use the glTF lighting model is proving difficult, due the “bonkers” way things like fresnel  offset and scale have been implemented. This issue is to be addressed.
    • It is believed that most existing content should render reasonably faithfully under the PBR / glTF, with the exception of the known issue of alpha blending on colour curves. Runitai Linden has a couple more ideas how this might be improved, but overall, it might come down to having to explain that the colour space is changing for glTF, and as a result some alpha blended content will need to be adjusted in order to render correctly.
    • As Advanced Lightning Model (ALM) will be enabled all the time in the PBR viewer (the Forward renderer will be disabled), the viewer’s quality settings are being updated so that Shadows will be disabled by default across a much wider range of settings, as these are what causes the significant performance hit when ALM in enabled, rather than ALM itself (but Shadows can still obviously be manually enabled).
    • This viewer also causes instrumentation regressions within the Performance Floater viewer, which will likely be addressed when the code is ready to be merged with the release version of the viewer. .
  • It is hoped that the simulator-side support can be deployed to an RC on the Main grid (Agni) in the near future in order to further advance viewer testing as that moves from project to RC status as well.

CCUG – Mirrors(!)

  • The “very next thing” LL plans to implement after PBR Materials reaches Release Candidate status is – mirrors!
  • These will be planar mirrors, so best suited to flat surfaces such as the face of a cube, rather than curved or spherical surfaces.
  • Mirrors will effectively be a real-time 1:1 rendering of what is seen within the scene that is being reflected, but with some limitations to cater for performance. Those limitations  / controls under discussion at the Lab include:
    • The mirror effect will only be generated in viewers that are very close to it.
    • Perhaps limiting the number of mirrors which can be active within a viewer to just one per scene (so if there are two mirrors close by your avatar, only one will be active at a time). Or allowing user select the number of mirrors they wish see “working” at any given time.
    • Adding a viewer Preferences option to enable / disable mirrors, depending on the user’s needs.
    • Nevertheless, even with precautions such as the above, there will be a performance impact in having real-time mirrors active in the viewer.
  • Mirrors will likely support LSL control over them.
  • It is already being recommended that mirror surfaces are only used as mirrors, not as a means of generating “reflections” in general – which should be left to reflection probes / cube maps.
  • It is hoped that the way the mechanism for rendering reflections onto a mirror surface would use the same channels as reflection probes – so when the mirror is seen from a distance, it uses the reflection rendering based on the local reflection probes, but when approached, the reflection probe rendering would fade out, and the real-time planar mirror reflection rendering would fade in.
  • That said, precisely HOW real-time mirrors will work is still subject to discussion and planning: at the moment, the focus has been only considering time in terms of ensuring the PBR work does not block opportunities for adding real-time reflections, and that they will play nicely with the PBR Materials work when they are being developed.

CCUG – Avatars / New Start Avatars / Ecosystem

  • A question was raised about the upcoming new mesh starter avatars previewed at SL19B in June2022. These have yet to be releases, and are not intended to compete with existing mesh avatars, also LL hopes creators will help develop an ecosystem in support for the avatars as the devkits for them are released – there is no confirmed release date for the avatars.
  • The above lead to a general discussion on the learning curves involved in getting to grips with avatar bodies and heads, trying to math heads to bodies, etc., the need for more discussions on avatar capabilities, helping people understand the avatar content creation process so they can join the ecosystem, etc.
  • The was an agreement that more discussion on avatar-related content creation, real and perceived limitations on the avatar system – particularly rigging clothing and attachments and the reliance on additional toolsets (e.g. AvaStar MayaStar, etc.), issues of supporting information available through the SL Wiki / Knowledge Base, etc. See In Brief for more on discussions / potential new meetings.
  • There are internal discussions going on at the Lab concerning avatar physics, enabling the simulator to “know” more bout the avatar, how it is being animated, having the simulator-side physics engine fully recognise the avatar body as a physical object (rather than just a simplified capsule), etc., via the likes of the Puppetry project and elsewhere, but solutions are still TBD.

In Brief

  • CCUG: Alpha blending issues on avatars – there was a general discussion on alpha stacking/ordering and blending issues, with Beq Janus’ blog post on the subject relating to avatars / outfits being referenced as a good primer on the issue and steps to mitigate problems.
  • TPVD: work is continuing on the Inventory thumbnails work, but nothing ready for any form of public release.
  •  TPVD: it has been suggested that LL might want to add code to the new Group Chat History functionality to indicate the end of historic Group chat within a Group chat tab / panel, as people appear to be getting confused as to why they are opening Group chat to find past conversations displayed (due to word about the new functionality taking time to spread).
  • TPVD: concern was raised that the allowance of lossless Normal Map under PBR will lead to a lot of abuse with people using it to upload lossless textures as well, which it was feared would hit people’s VRAM. Runitai pointed out that lossless does not necessarily hit VRAM, but does impact caching and bandwidth. This sparked a general conversation on textures, resolution, quality, etc. However, the risk of people abusing the upload was acknowledged, and store will be monitored for unexpected spike in usage after the release of PBR.
  • TPVD: a discussion on viewer development as support for AAA game-style rendering. Please refer to the video for details,
  • Both meetings: user on-boarding – at both the CCUG and the TPVD meeting it was suggested that there needs to be a regular user group meeting to discuss user on-boarding, engagement and retention and how to address these on an ongoing basis.
    • This led to a lengthy discussion on the issues of engagement + retention which illustrated one of the core issues in just discussing it: everyone has a different opinion on what “the problem” is with engagement / retention.  Some see it as primarily being an expense issue (the cost of creating a good-looking avatar); some see it as people being unable to find interesting this to do; some see it as being performance / hardware / overall appearance of SL.
    • The problem with the above is (and as demonstrated at the TPVD meeting particularly) it can lead to very siloed outlooks where disagreements as to “the problem” become the focus of conversations, rather than agreement that all of these issues can play a role, and as such, solutions need to be perhaps more “holistic” in nature and encompassing all of the perceived pain points.
    • It has been suggested that an upcoming CCUG or TPVD meeting could be utilised as a kick-off session for broader discussions about on-boarding, etc.

Next Meetings

  • CCUG: Thursday, March 2nd, 2023.
  • TPVD: Friday, March 16th, 2023.