[Bug]: Alpha Cutoff not working as in the SL main viewer #230
Description
Environment
Alchemy Beta 7.1.9.2516 (64bit)
Release Notes
You are at 56.3, 20.4, 2,793.5 in Dysfunctional Island located at simhost-03106841428dcfc7b.agni
SLURL: http://maps.secondlife.com/secondlife/Dysfunctional%20Island/56/20/2793
(global coordinates 108,600.0, 400,660.0, 2,793.5)
Second Life Server 2025-04-24.14648572313
Release Notes
CPU: Intel(R) Core(TM) i3-10100 CPU @ 3.60GHz (3599.99 MHz)
Memory: 16313 MB
Concurrency: 8
OS Version: Microsoft Windows 10 64-bit (Build 19045.5965)
Graphics Card Vendor: NVIDIA Corporation
Graphics Card: NVIDIA GeForce GTX 1060 6GB/PCIe/SSE2
Windows Graphics Driver Version: 32.0.15.6614
OpenGL Version: 4.6.0 NVIDIA 566.14
Window size: 1920x1012
Font Size Adjustment: 96pt
UI Font: Default
Monospace Font: Default
Chat Font: SansSerif
Script Font: Monospace
UI Scaling: 1.2
Draw distance: 256m
Bandwidth: 3000kbit/s
LOD factor: 2.5
Render quality: 4
Texture memory: 6029MB
Texture cache: 353MB / 6552MB (5.4% used)
Disk cache: 207MB / 8192MB (2.5% used)
RestrainedLove API: RLV v3.4.3 / RLVa v2.5.0.2516
libcurl Version: libcurl/7.54.1 OpenSSL/1.1.1w zlib/1.3.1.zlib-ng WinIDN nghttp2/1.62.1
J2C Decoder Version: OpenJPEG Runtime: 2.4.0
Audio Driver Version: FMOD Studio 2.02.26
Dullahan: 1.14.0
CEF: 118.4.1+g3dd6078+chromium-118.0.5993.54
Chromium: 118.0.5993.54
LibVLC Version: 3.0.21
Voice Server Version: Vivox 4.10.0000.32327.5fc3fe7c.571099
Compiler Version: MSVC 194234436
Packets Lost: 0/2,317 (0.0%)
June 20 2025 13:32:12
Description
This is reproduceable - When using the most recent Alchemy, objects using masked alpha and a Blinn-Phong default Transparent texture where the mask is set to 1 will be 100% transparent. SL viewer (7.1.15.1) displays the item as having strong islands of red and is not perfectly transparent.
Recently this led to some confusion which led to me investigating this. Other people using the default SL viewer can see this partially red image.
The solution has been to set the threshold to 50. However, the occurrence of this points to a fundamental difference in how transparency is being handled.
Reproduction steps
On Alchemy, rez any prim.
Set as Legacy (Blinn-Phong)
Set texture to Transparent
Set Type to Alpha Masking
Set Alpha Threshold to 1
Object will appear 100%% transparent in Alchemy
Using Second Life viewer, observe object. Note red "islands" of texture.