filament: Shadows not displaying for certain GLTF models

Describe the bug When rendering a model (in tandem with AR core for surface detection and positioning), certain GLTF models (loaded with the AssetLoader class from gltfio) doesn’t cast a shadow on the planes that are rendered. Here are the different models used:

1. Non-shadow casting model: trex.zip

2. Shadow casting model: scooter.zip

To Reproduce Steps to reproduce the behavior:

1. Load the gltf asset using AssetLoader.
2. Render a flat plane below the asset that will be loaded (set receive shadows to true)
3. Set directional lighting and cast shadows to true.
4. Place the gltf model on top of the plane
5. Assert that the scooter model renders a shadow but the trex model doesnt.

Expected behavior Both models should be rendering shadows

Screenshots

Smartphone (please complete the following information):

• Device: Pixel 4XL
• OS: Android 12

Additional context

• The t-rex model itself is receiving shadows from the direct lighting, it just doesn’t seem to want to cast shadows.