When loading a glb file with the new 4.x alpha version, the physics imposter seems to not get saved correctly:
To reproduce open this:
https://www.babylonjs-playground.com/#EGQ169
Open the debug tools, navigate through the nodes tree to the mesh and open it’s physics section. An undefined/nullpointer error will be thrown:
This only happens when using a glb or gltf file. Obj files work fine.
I suspect that this is the reason the collision detection is not working reliably for a more complex model in my project if I save it as glb. If I, however, save it as obj. everything works fine. Sadly I couldn’t reproduce the collision detection bug with this simple file.
EDIT: This example also has a collision detection bug. In around 1 of 10 times the sphere slips through the heart.
I was able to reproduce the mentioned bug about the non working collisions in a simplified version:
I modified this example: Babylon.js Playground from the docs to reproduce it.
Here is the non working example:
https://playground.babylonjs.com/#66PS52#19
I copied the method makePhysicsObject and adjusted it slightly for the ground box.
The glb file was exported from Blender 2.8 with the Khronos exporter. A link to the original Blender file is in the comments.
Physics impostors only can exist on meshes that have no parent or are part of a compound object (eg. parent is also a physicis impostor). If the parent of the imported cube is set to null it will collide:
eg. https://playground.babylonjs.com/#66PS52#20. Setting the parent to null might change the look as gltfs will have a -1 z scale applied due to gltf using a different handedness than babylon so let me know if you run into more issues but the way the weird shape is imported in the playground you linked should work.
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Thank you very much, that resolves the collision problem.
The undefined errors still happen.
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Is there a valid use case for having an object with an physics imposter which does not ignore the parent but whichs parent has no imposter (that situation i thought was a bug)?
If not than I think we should at least display a warning or even better redesign the api in a way that it doesn’t allow creating such an invalid state. I spent quite some hours trying to debug that problem and think others will run into the same situation.
When creating a compound impostor the child mesh impostors are added before the parent so adding an error message here might be a bit tricky.
