Glb rendering problem with v1.68.1

Hi there,
After updating PlayCanvas to version v1.68.1, I encountered a perplexing issue. The glb models that were originally displayed correctly now exhibit anomalies, causing them to appear damaged and incomplete (as shown in the image). When I rolled back to version v1.67.3, the issue disappeared. Hence, I suspect it might be a side effect of the version update.

The glb model was downloaded from Sketchfab (link here). I have tried to reproduce the issues I encountered as much as possible within a single repository. You can refer to my repo on GitHub, where simply running the Live server will reproduce the problem.

Another observation is that when I place the same glb model into the scene through the PlayCanvas Editor, the displayed model does not encounter the aforementioned issue. If possible, could you also explain why there is this difference?

I am curious if the situation I am facing is a known issue or if anyone can suggest how I should adjust it for better results.

Hi @Spencer.L ,

This is mostly likely an issue on the engine that’ll we’ll investigate ASAP. Thanks for reporting it.

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This seems to be an issue with your model - it has the same issues in threejs and babylonjs viewers. We had a small change in 1.67.3 to help this case, but have reverted it as it introduced other issues.

The problem seems to be with alpha blending being enabled on the mesh … which it should not.

The reason the Editor does not have this issue is that it’s using 1.67.3 … we’re just updating it to 1.68.1, so shortly that should reproduce the same issue.

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This change is likely related: Reverting recent glb alpha depth write change for transparent meshes by mvaligursky · Pull Request #5988 · playcanvas/engine · GitHub

You can either disable alpha blending for your mesh, or enable depth write as in that PR.

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Thank you for your response! It was fast and very detailed!
I would like to confirm if there is a chance that this issue will be fixed in the future?

As I explained, the issue is with the model, and all other glb viewers I tried display it the same way. The model needs to be fixed.

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Ok, thank you for your explanation, much appreciated!