[PBR] Trees render with too much transparency since PBR | Voters

[PBR] Trees render with too much transparency since PBR

tracked

Whirly Fizzle

Steps To Reproduce

Go to http://maps.secondlife.com/secondlife/Romantica/178/191/21
Observe how the palm trees look against the sky

Observed Behaviour

On PBR viewers, the palm tree leaves are very transparent, especially when viewed against the sky

On Pre-PBR viewers, the trees render as expected

The Pre-PBR image was taken using https://releasenotes.secondlife.com/viewer/6.6.16.6566955269.html
Both viewers set to Ultra graphics quality, and legacy midday. Though note the bug reproduces with any sky setting.
Original images that can be expanded to larger size
Pre-PBR: https://gyazo.com/83fb9f47b52a8fc7e82270fe596533b1
PBR: https://gyazo.com/70dfd6c4becf6753db2b70a4f049902d

March 19, 2024

Atlas Linden

marked this post as

tracked

Thanks Whirlz! This has been linked up to an internal GitHub issue

Tayln Osbourne

My best assumption on what's going on is that since PBR enforces linear alpha blending (as per the glTF 2.0 specification), the texture may not be fully opaque where there's leaves, leading to the darker color being washed out by the sky.

In theory, it could be fixed by making BlinnPhong use sRGB blending, but it would likely result in performance loss from having a more complex shader.

Whirly Fizzle

Probably related:

[BUG-234546] [PBR] Rendering Problem of trees in foreground and shrubs in background #11454

https://github.com/secondlife/jira-archive/issues/10947 -

[BUG-233924] [PBR] Wrong alpha sorting of inworld objects #10947