Day: July 2, 2022

2022 CCUG meeting week #26 summary: materials + graphics update

Posted on by Inara Pey
The Pond, May 2022 – click any image for full size

The following notes were taken from my audio recording and chat log of the Content Creation User Group (CCUG) meeting held on Thursday, June 30th 2022 at 13:00 SLT. These meetings are chaired by Vir Linden, and their dates and times can be obtained from the SL Public Calendar.

This is a summary of the key topics discussed in the meeting and is not intended to be a full transcript.

Official Viewers Update

One Wednesday, June 29th, The Maintenance M(akgeolli) RC viewer, version 6.6.1.572458 was promoted to de facto release status.

No changes to the rest of the official viewers through until Thursday, June 30th, leaving them as:

  • Release channel cohorts:
    • Nomayo Maintenance RC (Maintenance N) viewer, version 6.6.1.572179, June 1.
  • Project viewers:
    • Performance Floater project viewer, version 6.5.4.571296, May 10.
    • Mesh Optimizer project viewer, version 6.5.2.566858, dated January 5, issued after January 10.
    • Legacy Profiles viewer, version 6.4.11.550519, dated October 26, 2020.
    • Copy / Paste viewer, version 6.3.5.533365, dated December 9, 2019.

Materials and PBR Work

Please also see previous CCUG meeting summaries for further background on this project.

Outline of Work

  • Work on an implementation of reflection probes which can be used both with PDR shading and with legacy content.
    • The overall aim of this work is to provide a means to support more physically accurate reflections in SL than can be currently generated (seen as a requirement for PBR support).
    • It applies to both PBR generated content, once available, and to legacy content.
  • Creating a materials type with an associated inventory asset. This  will initially comprise the ability to copy a texture entry (with its specific parameters) to inventory, to be followed by initial work to work implement a PBR graphics pipe in the viewer.
  • Normals will likely be MikkTSpace, as per the glTF specification, but work needs to be done to see if supporting this could lead to clashes with the current normal maps rendering. This does mean that current Normal maps will not work on PBR materials.
  • The initially supported capabilities are:
    • RGB albedo + transparency.
    • RGB Occlusion/Roughness/Metalness: R = occlusion, G = roughness; Blue = metalness.
    • RGB emissive.
    • RGB normal (- alpha).
    • Double-sized supported (disables backface calling before issuing the draw call).
    • Two-sided lighting (so if the back of a triangle is visible, it flips the normal around).
  • In addition:
    • There will be an ability to “preview” materials on an item within your own viewer (similar in nature to Local Textures) before actually uploading them.
    • LSL support is still being defined, but should at least allow individual texture UUIDs to be replaced under script control.
    • The approach being taken is to may the system extensible so that further capabilities / plug-ins / options can be added with relative ease in the future.
    • However, Displacement maps will not initially be supported due to not being defined in the core of glTF 2.0; nor will any extensions that are not adopted into the core glTF standard (either glTF 2.0 or 3.0).

Materials Progress

Screen Cap from a video by Runitai Linden showing (l) the basic PBR Materials UI, and right, materials assets in inventory, which can be dragged / dropped onto objects / object faces in-world (centre)
  • There is further work required on the back-end inventory services and asset store, and on some of the shaders in the viewer, before any of this work is ready for public testing on Aditi.

ALM Proposal / Work – Recap

At the #week #23 TPVD Developer Meeting (notes here), it was indicated that LL are “leaning” towards removal of the non-Advanced Lighting Model (ALM) (aka “forward rendering”) rendering path from the viewer, leaving just ALM rendering (aka deferred rendering”).

  • Were this to be done, it would only be done if it can be shown that this does not adversely impact performance (e.g. ALM runs roughly as well as non-ALM for those using the latter) on the broad cross-section of hardware most commonly operated by SL users.
  • The work will include:
    • A slider to manage the number of rendered local lights to lightening the load of rendering illumination on lower specification systems.
    • A “data saving mode” primarily intended to help those on metered connections by culling the download of additional materials / PBR maps and potentially downloading lower resolution textures mips, all of which will reduce the data passing over their connections. However, it will result in a much poorer visual experience once the PBR work has been implemented, and the hope is the mode will only be used in the minority of cases.
  • Given the ongoing work to support PBR and a more rounded set of materials, moving to deferred (ALM) rendering without fallbacks to non-ALM rendering – providing, again, the caveats noted above can be met / implemented – will in general help ensure a more reliable / consistent viewing experience across a broad range of hardware.

In Brief

  • The work to make full use of available video memory on a client computer is being put out to a hardware compatibility lab to help ensure the code changes are doing what they are supposed to be doing on a wide variety of hardware. These tests will also look at the impact of running the viewer with ALM active all the time across all hardware configurations.
  • On Animation:
    • The Puppeteering project highlighted at Grumpity and Mojo Linden’s Meet the Lindens session came in for criticism, but it was suggested people give the system a chance to reach a more advanced stage before judging, as the video presented in the talk does not do the work justice.
    • Vir indicated that while there is an understanding at the Lab that people would like the animation system overhauled:
      • Such a project currently isn’t on the roadmap
      • However, consideration is being given to allowing an on-the-fly adjustment of animation priorities.
      • Requests for additional animation work were requested via Feature Request Jira.
    • Runitai Linden suggested that as glTF supports animations it might – in the future – be a possible option for animation improvements. However, note that moving in this direction is also not part of the current roadmap.

Next Meeting

  • Thursday July 7th, 2022.