Lightrun Answers was designed to reduce the constant googling that comes with debugging 3rd party libraries. It collects links to all the places you might be looking at while hunting down a tough bug.
And, if you’re still stuck at the end, we’re happy to hop on a call to see how we can help out.
AlphaMode / alphaCutoff information is lost when re-exporting Project Polly in Blender 2.90
See original GitHub issueDescribe the bug
I have tried loading the Project Polly model in Blender 2.90 and outputting it in glTF format.
However, some information seems to be missing. For example, the alphaMode / alphaCutoff.
To Reproduce Steps to reproduce the behavior:
- Download the following file.
https://github.com/KhronosGroup/glTF-Blender-Exporter/blob/master/polly/project_polly.blend
(Probably created in Blender
2.79) - run Blender
2.90 - Open
project_polly.blend - Export to
project_polly.gltfFormat : [gltF Separate (.gltf + .bin + textures)] [x] Cameras - Check the contents of
project_polly.gltf.alphaMode/alphaCutoffis not output.
| Material name | glTF JSON |
|---|---|
| Location Transparent |  |
| Polly Display |  |
Expected behavior
| Material name | glTF JSON |
|---|---|
| Location Transparent |  |
| Polly Display |  |
The output results are expected to be similar to the glTF file below. https://github.com/KhronosGroup/glTF-Blender-Exporter/blob/master/polly/project_polly.gltf
Screenshots
| Blender 2.79 glTF Export results | Blender 2.90 glTF Export results |
|---|---|
 |
 |
.blend file/ .gltf https://github.com/KhronosGroup/glTF-Blender-Exporter/blob/master/polly/project_polly.blend
Version
- OS: Windows 10 Version 1909
- Blender Version 2.90.1
Issue Analytics
- State:
- Created 3 years ago
- Comments:10 (4 by maintainers)
Top Results From Across the Web
Top Related Medium Post
Top Related StackOverflow Question
Troubleshoot Live Code
Top Related Reddit Thread
Top Related Hackernoon Post
Top Related Tweet
Top Related Dev.to Post
Top Related Hashnode Post
Not to make things more complicated, but Polly has always abused alpha blending to look like glass, which was never the intention of alpha in glTF. Alpha is supposed to indicate the absence of a material, such as the edge of a leaf in a quad, or medical gauze wrap with lots of holes too small to see.
For glass, we recently ratified a new extension,
KHR_materials_transmission. Among other things, this allows full specular reflections to take place on the clear parts of the glass (which alpha blending does not do). It also allows for frosted glass (via material roughness), and lets path tracers know they can trace reflections in the glass.Blender support for this is documented in 2.91.
Sounds like we should update the source
.blendsample file to be compatible with 2.90? At least for the material settings portion of the question.