GltfLoader sourceIndex NPE on SheenWoodLeatherSofa model

[stephengold]

SheenWoodLeatherSofa.gltf was added to the glTF-Sample-Assets test suite in May 2024.
https://github.com/KhronosGroup/glTF-Sample-Assets/tree/main/Models/SheenWoodLeatherSofa

When I try to load it using jme3-plugins, I get warnings followed by a crash:

Mar 05, 2025 11:05:51 AM com.jme3.scene.plugins.gltf.CustomContentManager readExtension
WARNING: Could not find loader for extension KHR_materials_sheen
Mar 05, 2025 11:05:51 AM com.jme3.scene.plugins.gltf.CustomContentManager readExtension
WARNING: Could not find loader for extension KHR_materials_specular
com.jme3.asset.AssetLoadException: An error occurred loading SheenWoodLeatherSofa/glTF/SheenWoodLeatherSofa.gltf
	at com.jme3.scene.plugins.gltf.GltfLoader.loadFromStream(GltfLoader.java:181)
	at com.jme3.scene.plugins.gltf.GltfLoader.load(GltfLoader.java:107)
	at com.jme3.asset.DesktopAssetManager.loadLocatedAsset(DesktopAssetManager.java:274)
	at com.jme3.asset.DesktopAssetManager.loadAsset(DesktopAssetManager.java:390)
	at com.jme3.asset.DesktopAssetManager.loadModel(DesktopAssetManager.java:441)
	at com.github.stephengold.wrench.test.CompareLoaders.loadModel(CompareLoaders.java:889)
	at com.github.stephengold.wrench.test.CompareLoaders.loadModel(CompareLoaders.java:855)
	at com.github.stephengold.wrench.test.CompareLoaders.onAction(CompareLoaders.java:496)
	at jme3utilities.ui.DefaultInputMode.onAction(DefaultInputMode.java:186)
	at com.jme3.input.InputManager.invokeActions(InputManager.java:174)
	at com.jme3.input.InputManager.onKeyEventQueued(InputManager.java:474)
	at com.jme3.input.InputManager.processQueue(InputManager.java:871)
	at com.jme3.input.InputManager.update(InputManager.java:923)
	at com.jme3.app.LegacyApplication.update(LegacyApplication.java:810)
	at com.jme3.app.SimpleApplication.update(SimpleApplication.java:249)
	at com.jme3.system.lwjgl.LwjglWindow.runLoop(LwjglWindow.java:707)
	at com.jme3.system.lwjgl.LwjglWindow.run(LwjglWindow.java:797)
	at java.base/java.lang.Thread.run(Thread.java:840)
Caused by: java.lang.NullPointerException: Cannot invoke "java.lang.Integer.intValue()" because "sourceIndex" is null
	at com.jme3.scene.plugins.gltf.GltfLoader.readTexture(GltfLoader.java:759)
	at com.jme3.scene.plugins.gltf.GltfLoader.readTexture(GltfLoader.java:739)
	at com.jme3.scene.plugins.gltf.GltfLoader.readMaterial(GltfLoader.java:650)
	at com.jme3.scene.plugins.gltf.GltfLoader.readMeshPrimitives(GltfLoader.java:473)
	at com.jme3.scene.plugins.gltf.GltfLoader.readNode(GltfLoader.java:252)
	at com.jme3.scene.plugins.gltf.GltfLoader.readChild(GltfLoader.java:301)
	at com.jme3.scene.plugins.gltf.GltfLoader.readScenes(GltfLoader.java:218)
	at com.jme3.scene.plugins.gltf.GltfLoader.loadFromStream(GltfLoader.java:155)
	... 17 more

I discovered this issue while testing JME v3.8.0-alpha4. However, the behavior hasn't changed since at least JME v3.2.4-stable, so I don't consider this a regression.

[javagl]

This was, under the hood, caused by the fact that this asset uses (and requires) the EXT_texture_webp extension for its WEBP textures.

With #2628 , trying to load this asset will now cause an
AssetLoadException: Extension EXT_texture_webp is required for this file.

If course, the KHR_materials_sheen extension is not supported either. If this extension is supposed to be tested, dedicatedly, then the CompareSheen asset should be used. The sheen extension is only in extensionsUsed (and not in extensionsRequired). This means that this specific asset can be loaded. It will (only) print a warning
WARNUNG: Extension KHR_materials_sheen is not supported, please provide your own implementation in the GltfModelKey

It will look like this:

Which is not "correct", visually, but it is what it is when the extension is not supported.

@stephengold I'll leave it to you whether you

• close this issue
• and/or change the title and contents of this issue (which may be a bit messy...)
• and/or open a new issue for the KHR_materials_sheen support
  (even though this is just one random material extension, and there are many material extensions that are not supported...)

EDIT: Note that an issue about WEBP support already exists, at #2616 . It is not specific for the EXT_texture_webp glTF extension, but general WEBP support is a precondition for implementing that extension anyhow.

[stephengold]

Thank you for your help, @javagl !