2023 week #26: SL CCUG meeting summary

The following notes were taken from my audio recording and chat log transcript of the Content Creation User Group (CCUG) meeting held on Thursday, June 15th, 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.
• Usually chaired by Vir Linden, and dates and times can be obtained from the SL Public Calendar.
• Conducted in mixed voice and text chat. Participants can use either when making comments  or 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.

Viewer News

• Maintenance T RC viewer updated to version 6.6.13.580700 on Wednesday, June 28th.
• The GLTF viewer updated to version 7.0.0.580717 on Tuesday, June 27th.

The rest of the official viewers currently in the pipeline remain as:

• Release viewer: Maintenance S RC viewer, version 6.6.12.579987, dated May 11, promoted May 16.
• Project viewers:
  • Second Life Project Inventory Extensions viewer, version 6.6.13.580656, June 26 see my overview for details.
  • Emoji project viewer, version 6.6.13.580279, May 30.
  • Puppetry project viewer, version 6.6.12.579958, May 11.

In addition:

• Maintenance T is likely the next RC viewer remains the next in line for promotion to de facto release status.
• The Emoji project viewer is liable to see further improvements to the Emoji picker in the UI.

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.
• There is a general introduction / overview / guide to authoring PBR Materials available via the Second Life Wiki.
• For a list of tools and libraries that support GLTF, see https://github.khronos.org/glTF-Project-Explorer/
• Substance Painter is also used as a guiding principal for how PBR materials should look in Second Life.
• Up to four texture maps are supported for PBR Materials: the base colour (which includes the alpha); normal; metallic / roughness; and emissive, each with independent scaling.
• Given the additional texture load, work has been put into improving texture handling within the PBR viewer.
• 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.
• The overall goal is to provide as much support for the glTF 2.0 specification as possible.
• To provide support for reflection probes and cubemap reflections.
• The viewer is available via the Alternate Viewers page.
• Please also see previous CCUG meeting summaries for further background on this project.

Status

• The new RC viewer includes the automatic adjustment to make skies “PBR-ified” (so the checkbox in Graphics Preferences to disable automatically apply reflection probe ambience on skies that do not have it set, so they will be set to a default of 1). Probe ambience must now be set to 0 through the sky settings to deactivate HDR rendering (so no dynamic exposure so the sky is not brightened, and objects with PBR materials will appear duller than intended), and tone mapping is turned off.
  • However, there is a recognised bug related to probe ambience (BUG-234060 “[PBR] Simulator Clamping Environment’s Reflection Probe Ambience to 1”, and it is hoped a fix for this will be in the next simulator build – although it may take a while for the build to make its way into a deployment.
• The-user supplied PBR content created on Aditi is being transferred to the PBR regions on the Main grid in readiness for more widespread viewing / testing.
• The LDPW will be producing a PBR demonstrator which will be available through the viewer library.
• The simulator-side support for glTF Materials is due to be expanded with further simulator RC deployments, which will notably include some sandbox environments.
• However, it should be noted that:
  • Any glTF / PBR materials content created within these environments which is taken and then rezzed in any region that is not Materials-enabled, will become “material-less” in a non-recoverable way, and will need to be recreated.
  • Because of the above point, until the glTF support is fully gird-wide, any attempts to put PBR-enabled goods on the Marketplace will be sanctioned.
• General bug fixing on both the simulator and the viewer is continuing.

PBR Terrain

• Per past meeting notes, Cosmic Linden is prototyping the application of PBR materials on terrain (see this blog post for more).
• Further work on bug fixing, including correcting an issue with triplanar mapping to the for terrain repeats, particularly on steep elevation changes (so as to avoid the all-too familiar “stretching” seen with textures).
• Important notes with this work:
  • It is not terrain painting. It is the application of PBR materials – terrain painting is described as “something that’s on the radar” at LL.
  • The work does not include support for displacement maps.
  • The work is currently only viewer-side, with no corresponding server-side support, the idea here being to prototype what might be achieved and testing approaches / results.

Level of Detail (LOD) Discussion

• Level of detail (LOD) refers to the complexity of a 3D model representation. In short the idea is to reduce the load on the rendering system by reducing the complexity of the 3D object based on various of criteria (e.g. the distance of the object from the viewer / camera) and using various techniques.
• Second Life uses the approach of Discrete Levels of Detail (DLOD) method – the use of discrete versions of the original with decreased levels of geometric detail to replace the more complex models using an algorithm primarily based on distance. This has both positives and negatives, some rooted in poor modelling practices by some content creators, others are inherent to flaws within SL itself.
• In looking at glTF and mesh imports in the future,  LL is considering moving towards more automated and better optimised means of creating LODs to try to reduce some of the current issues.
• One idea under consideration to achieve this is to leverage Simplygon (or see the Wikipedia entry), which although a proprietary tool, is available as a plug-in for a number of 3D modelling towards (including Blender); the idea being the glTF importer consume whatever output is generated by Simplygon at the creator’s end of the workflow (it being noted that “simply” integrating Simplygon into SL isn’t feasible).
  • Such an approach would offer advantages of optimisation whilst leaving the current upload process in place for those wishing to continue to use it, together with the continued ability to manually create LODs.
• Some concerns over this possible approach raised at the meeting were:
  • It does not address issues of avatar complexity, which is potentially the biggest viewer performance hit – although in fairness, avatar complexity is really an issue requiring its own focus / project.
  • The nature of some of the Simplygon licensing statements (concern about which might be a mix of the genuine and a basic misunderstanding of legal terms used with regards to “how the Internet works”, so to speak; an issue we had back when LL changed some of the terminology within the SL TOS in 2013).
• While there are other optimisations tools available, given the state of flux with things within the open source environment, and given Simplygon is recognised as an “industry standard”, offering a means to take output from in and bring it into Second Life is currently seen as the best strategy by the Lab, subject to the concerns raised about the licensing requirements.

In Brief

• There have been reports of Animesh objects changing / becoming stuck in their lowest LOD in various circumstances, including on region crossing (see BUG-233691 “Animesh re-renders at lowest LOD for extended interval after long-range llSetRegionPos” + listed duplicates). This is believed to be a bounding box issue, and a fix is being developed which should hopefully make it into the next update of the Maint T RC viewer.
• For PBR, the questions was raised about converting older content with the current Blinn-Phong materials to PBR where the base colour map is not available. The recommendation is that the two are kept separate: if the base colour map is not available for conversion, that Blinn-Phong should continue to be used. No attempt on LL’s part will be made to try to combine the two (PBR / Blinn-Phong) through any kind of conversion tools, as the two are currently entirely separate, allowing creators / users to apply PBR to items which may already have Blinn-Phong, and if the results aren’t good, strip the PBR away and immediately revert to the Blinn-Phong materials. Any attempt to allow “blending” between the two approaches will immediately break this.
• One consideration actively being worked on within the Lab is glTF licenses and Second Life being able to recognise these. Licences tend to be built-in to glTF complaint 3D models, so as the end goal of the glTF project is to effectively be able to take a glTF model from (say) Sketchfab and drop it into SL, this should be done in respect of the object’s licensing (e.g. if it has a Creative Commons Non-Commercial license, it can be imported into SL but not re-sold after the fact or placed on the SL Marketplace).

Next Meeting

• Thursday, July 6th, 2023.

† The header images included in these summaries are not intended to represent anything discussed at the meetings; they are simply here to avoid a repeated image of a gathering of people every week. They are taken from my list of region visits, with a link to the post for those interested.