combineNodes conversion issue

[lilleyse]

When running a billboard model through the pipeline I noticed that when combineNodes runs the processed model is incorrect. Is it because the root node has a non-identity matrix?

treeBillboard.txt

[lasalvavida]

So, this is a tricky one. combineNodes flattens out the node transforms onto the points correctly. However, even though this model declares a Y-Up transform in the glTF, the vertex shader discards the rotation and scale of the model matrix and applies the Y-Up transform itself. After conversion, the points are already Y-Up, and then the shader applies the transform again.

If you delete the Y-Up transform node and make Plane the root node, this model displays correctly before and after conversion.

I don't think there is a reasonable way to handle people doing custom modifications in the vertex shader like this.

[lilleyse]

Ok, thanks for looking into this - and yes it's a weird case.