Shader exception when loading GLTF 2.0 model with tangents

CesiumGS / cesium

An open-source JavaScript library for world-class 3D globes and maps :earth_americas:

https://cesium.com/cesiumjs/

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Shader exception when loading GLTF 2.0 model with tangents #10856

Closed xtassin closed 1 year ago

xtassin commented 2 years ago

Loading a model that was converted from DAE using COLLADA2GLTF and with exported tangents/binormals leads to Cesium crashing with a shader exception.

I also documented this issue on the COLLADA2GLTF repo and waiting for feedback on this issue. https://github.com/KhronosGroup/COLLADA2GLTF/issues/294

As a note, when working from 3DS max, is it better to use COLLADA2GLTF or OBJ2GLTF (which one is better maintained?). Any other converter/exporter recommended?

lilleyse commented 2 years ago

Yes, it seems like COLLADA2GLTF is producing invalid tangents. They should be VEC4 instead of VEC3. That said, the test model doesn't have a normal texture so you don't need tangents. Is there an option to export DAE without tangents?

OBJ2GLTF is better maintained but OBJ is a more limited format - no node hierarchy, no animations, no tangents, etc.

I haven't tried the Babylon 3DS Max plugin before, but it looks good: https://doc.babylonjs.com/features/featuresDeepDive/Exporters/3DSMax_to_glTF

xtassin commented 2 years ago

Test model was just for testing ;) I do need tangents in my shaders. (but yes, you can export DAE without tangents if needed)

Babylon plugin is interesting but gave mixed results so far, for me. File weight is very high (not sure why), I could not manage to enable draco compression, etc.

Ariakim-Taiyo commented 2 years ago

Once thing you might be able to consider is exporting the model as DAE and then importing it to blender and using the built in GLTF 2.0 exporter there. I've had no issues with that exporter so far, but I can't be certain if it would work correctly with models made in a separate program.

xtassin commented 1 year ago

@lilleyse, I keep experimenting with various options to generate GLTF2.0 models and I was wondering if you would share some advice, best practices or if you had some roadmap for new tools for artists working with GLTF and Cesium?

Here is so far what I found out:

COLLADA2GLTF is outdated and has this tangent problem. I am not sure this tools has any future: can you confirm?
3DSMax Babylon plugin is the best option in my case (working with 3DSMax) and after some time to master it gives nice output, proper tangents if needed and Draco compression when libs are provided.
Blender exporter works well too but add extra import/export steps.

I am still stuck with the problem of either using native exported PBR shaders or find a way to apply multiple materials while using Cesium's customShader API (as described here https://community.cesium.com/t/dropping-support-for-gltf-1-0/19969/20?u=xavier_tassin)

ggetz commented 1 year ago

Closing this issue as it appears to be a data problem rather than a CesiumJS bug.