2023 week 14: SL CCUG meeting summary

Perpetuity, February 2023 – 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, April 6th, 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 usually 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.

Additional note: unfortunately, physical world matters meant I missed the initial part of the meeting, and as it is held in voice, there is little by way of chat transcript to reflect initial discussions prior to my arrival.

Official Viewer Status

On April 6th:

  • Maintenance T(ranslation) RC viewer, version, was issued.
  • The PBR Materials / reflection probes project viewer updated to version

The rest of the current official viewers remain as:

  • Release viewer: Maintenance R viewer, version, dated March 28, promoted March 30th.
  • Release channel cohorts:
    • Maintenance S, version, March 31st.
    • Performance Floater / Auto FPS RC viewer updated to version, April 4th.
  • Project viewers:
    • Puppetry project viewer, version, December 8, 2022.

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.


  • The viewer has been updated to maintain parity with the release viewer, and work continues to get the viewer to a position where it can move to RC status.
    • Once it does go to RC status, it is expected to remain there for “a few months”.
  • Currently, the viewer is at a point where creators who wish to make content using PBR tools such as Substance Painter can do so and work to the rule-of-thumb that if it looks the same in both Substance Painter and the glTF viewer, than all is well and good – BUT, if the SL version looks noticeably different in the viewer, then a bug report should be filed, the issue should not be worked around.
  • Getting the simulator support for glTF moved to Agni is now being considered.
  • With regards to Bakes on Mesh, glTF Materials work in a similar manner to the current materials – the result of the BoM process gets fed into the base colour (+ the emissive map) like it does with the diffuse map for materials at present.
    • This does not mean BoM is glTF materials enabled; that still requires an update to the Bake Service to support materials data.
    • Updating the Bake Service is still seen as a “high value” future project.
  • The Sun midday position of the Sun has been adjusted so that it is no longer directly overhead, but is angled to appear as it would at a latitude of around 40ºN/S in spring.
Left: the glTF viewer repositions the midday Sun so it is in similar position as it would appear in the physical world at a latitude of around 40ºN/S in the spring, as opposed to being directly overhead as seen in the image on the right. Credit: Runitai Linden
  • Automatic alpha masks are turned off in the PBR viewer, and are likely to remain this way unless a compelling reason emerges for this not to be the case. So the Develop(er) → Rendering → Automatic Alpha Masks option for deferred rendering is off (and the one for forward rendering removed, as the glTF viewer does not support forward rendering).

HDRi Sky Rendering

  • In order to  get parity with High Dynamic Range Imaging (HDRi) environment maps has meant the sky as rendered on the glTF viewer is essentially HDR with added dynamic exposure. Without this change, the sky was lighting everything as if it were a “giant blue wall” rather than a bright sky.
  • This has impacted EEP (the Environment Enhancement Project, and means that the sky can look over-exposed under some settings.
  • LL is trying to zero in on a sky of sky parameters that is acceptable to most EEP settings. However, the issue is particularly noticeable for EEP settings which use “day for night” (e.g. they utilise dark sky tinting, etc., and replace the Sun texture with a planet or moon or some such, because the HDR rendering assumes that because the Sun “up”, there should be a brighter lighting used in the sky.
  • The choice here is:
    • Should the parameter be adjusted for uniformity (and some EEP settings require adjustment), or
    • Should additional control be supplied to allow additional control over the sky brightness, etc., to deal with EEP settings  where the above issues occur?
  • The problems with this second approach are that:
    • It “severely” fragment the expected colour space in the process, leaving content creators having to work with multiple lighting models (e,g. as with working with ALM on or off at present)?
    • It is akin to LL removing the ability to disable ALM in the PBR viewer and remove the older forward rendering code, only to then implement another “button” to alter the environment rendering, rather than keeping things uniform.
  • This topic has been the subject of heated debate within the Content Creation Discord channel.

In Brief

  • Priorities for graphics / content creation work after glTF Materials are currently planar mirrors and then glTF mesh imports.

Next Meeting

  • Thursday, April 20th, 2023.


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