Open vorg opened 1 month ago
The glTF alphaMode is used for alpha-as-coverage, NOT for physically-based transparency (i.e. this extension). If alpha-as-coverage is not being used, the blend mode of the material should be set to "OPAQUE" even though it is transparent. Again, it's helpful to think of alpha-as-coverage as whether the physical surface is there or not. transmission applies to the surface material that exists. Note that alpha-as-coverage can still be used along with transmission as shown in the example below.
But filament and three.js allow alpha:
https://github.com/google/filament/commit/25a82911016e8a9d6917688d530ea54c4d84a5c2
In the previous version of pex-renderer we could combine transmission with alpha blending and have reflective glass 50% faded out based on
baseColor.a
opacity. That is no longer possible. Setting alpha blending disables transmission. What does the glTF spec says here?