glTF Export shouldExportNode changed

[JoeyKo]

Hey Babylonjs Forum!!
I upgraded the babylonjs version to 7.40.3.
And I found the GLTF2Export.GLTFAsync function shouldExportNode not includes all nodes, just root node
Is this a breaking change or just a bug?

[srzerbetto]

Hello @JoeyKo , how are you doing?

I will double check. Can you provide a Playground with an example?

[JoeyKo]

@srzerbetto Here’s the PG

Babylon.js Playground

[srzerbetto]

@alexchuber , maybe we have a bug in the Serializer?

[srzerbetto]

Actually, I think the problem is on the “node.isDescendantOf” call. This method only returns true for the “RootNode” node. The other nodes that it prints are the ones directly bellow “RootNode”, they are because the Serializer investigates if it should export them or not, but the result of “node.isDescendantOf” for those nodes is false. Therefore, the Serializer will not continue to parse the nodes down the tree.

I think this is expected, right? If a node should not be exported, that also means its children should not be exported.

[JoeyKo]

I’m sure it’s not about the node.isDescendantOf call.

I just downgraded babylonjs to version 7.32.5, with the same code, the console shows all nodes.

Or you can just test in the current PG, switch version from latest to 6.49.0, And the console shows all nodes.

[srzerbetto]

Here, printing the value of node.isDescendantOf(root), it shows it returns false for those nodes.

Available Mesh SeaGulf | Babylon.js Playground

When changing to 6.49.0 it returns true.

[srzerbetto]

Actually, I think you are right. The current behavior is, we start parsing the scene from the root. Since “cgmszj_root” is not “isDescendantOf” the root node (it’s actually its parent), we don’t continue to parse down the tree.

This was probably not the behavior the older version of the Serializer was doing. It was either traversing the tree in a different order, or continuing to parse children nodes even when the parent should not be exported.

[alexchuber]

We can look into a fix for this The only issue I foresee is how we collapse camera and lights into their parents. I think that’s the main reason we skip the children of skipped nodes.

[alexchuber]

Allow exporting children of skipped nodes in glTF exporter by alexchuber · Pull Request #16017 · BabylonJS/Babylon.js · GitHub should address this. Feel free to take a look and test the snapshot playground

[JoeyKo]

@alexchuber @srzerbetto Really appreciate you taking care of it so fast.