3D Tiles Model appeared with face orientation flipped (backface culling)

Cesium for Unity
1

Hello,

Hopefully I can get some insights from this forum.
So currently I’m trying to upload a customized model of a building, and since I’ve issues with Blender 4.2 Cesium add-on to export, so I’m manually export the model to the fbx file format and zip it together with the textures.

Uploaded the zip file to my Assets in Cesium ion, and it looks fine in the preview windows:

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However, when I tried to import it in Unity, it appears with its faces orientation flipped.

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I’ve tried to:

  1. Change to different file type (gltf, glb, obj)
  2. Trying to use Unity to export the model
  3. Flipped the normals in blender and export it (in the hope that it would flipped the other wat around in Unity)

But all of the above didn’t solve my problem. Thank you in advance for any suggestion or solution. :grinning:

2

Hi @dwirizki, welcome to the community!
I’m not quite sure what would cause that. Can you share the model with us so that we can take a look? Please privately send me the ion asset ID, a token that can be used access it, and a statement that I have your permission to access it for debugging purposes.

3

Hi Kevin,

Thank you for your reply. And how to send it privately to you? Apologies, since I’m relatively new to this community.

4

Looks like you figured it out. But for future reference for others: just click on my name and then click “Message”.

5

Hi @dwirizki,
Thanks for sending through your model. I looked into this problem and just opened a draft PR to fix it:

The immediate problem was that we weren’t supporting the glTF doubleSided property. I’m still struggling to get this working 100% across all of Unity’s render pipelines, but hope to get it into the next release. In the meantime, you can work around the problem by copying the CesiumDefaultTilesetMaterial and in the copy setting the Cull Mode to OFF in URP and the built-in pipeline, or the Double-Sided property to TRUE in the HDRP pipeline. Then, select this new material as the “Opaque Material” on your Cesium 3D Tileset component.

This workaround isn’t perfect, because the normals on the back faces (which are the front faces in your model) will point in the wrong direction in URP and built-in, and so the lighting may be a bit strange. You can fix this by inserting a few new nodes in the “glTF Normal Texture” section of the CesiumDefaultTilesetShader.

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6

We just released Cesium for Unity v1.12.0, which fixes this problem.