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InterpolationTest.gltf fails to load, crashes with "Inconsistent animation sampling"

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
48/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
java
Domain
computer-graphics

Research direction

Start by loading Models/InterpolationTest/InterpolationTest.gltf through the jme3-plugins path shown in the report, then read GltfLoader.readAnimation and TrackData.checkTimesConsistency. Use the stack trace to follow how animation sampling is validated. Done means the asset loads without the reported AssetLoadException and the relevant behavior is covered by an appropriate test.

Written by the indexing model from the issue text.

Description

InterpolationTest.gltf has been included in the glTF-Sample-Assets test suite since its inception.
https://github.com/KhronosGroup/glTF-Sample-Assets/tree/main/Models/InterpolationTest

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

Mar 05, 2025 10:33:28 AM com.jme3.scene.plugins.gltf.GltfLoader readAnimation
WARNING: JME only supports linear interpolation for animations
Mar 05, 2025 10:33:28 AM com.jme3.scene.plugins.gltf.GltfLoader readAnimation
WARNING: JME only supports linear interpolation for animations
com.jme3.asset.AssetLoadException: An error occurred loading InterpolationTest/glTF/InterpolationTest.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: com.jme3.asset.AssetLoadException: Inconsistent animation sampling 
	at com.jme3.scene.plugins.gltf.TrackData.checkTimesConsistency(TrackData.java:191)
	at com.jme3.scene.plugins.gltf.TrackData.update(TrackData.java:175)
	at com.jme3.scene.plugins.gltf.GltfLoader.readAnimation(GltfLoader.java:906)
	at com.jme3.scene.plugins.gltf.GltfLoader.loadFromStream(GltfLoader.java:162)
	... 17 more

I discovered 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.

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