ArrayIndexOutOfBoundsException when software skinning an imported glTF

In current "master" branch, loading a model from https://github.com/capdevon/sharefile/blob/main/RPM_RandomAvatar.glb :

Mar 29, 2024 12:39:27 PM com.jme3.system.JmeDesktopSystem initialize
INFO: Running on jMonkeyEngine 3.8.0-SNAPSHOT
 * Branch: master
 * Git Hash: 9452078
 * Build Date: 2024-03-29
Mar 29, 2024 12:39:27 PM com.jme3.system.lwjgl.LwjglContext printContextInitInfo
INFO: LWJGL 2.9.5 context running on thread jME3 Main
 * Graphics Adapter: null
 * Driver Version: null
 * Scaling Factor: 1
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.jme3.util.ReflectionAllocator (file:/home/sgold/NetBeansProjects/jmonkeyengine/jme3-core/build/libs/jme3-core-3.8.0-SNAPSHOT.jar) to method sun.nio.ch.DirectBuffer.cleaner()
WARNING: Please consider reporting this to the maintainers of com.jme3.util.ReflectionAllocator
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
Mar 29, 2024 12:39:27 PM com.jme3.renderer.opengl.GLRenderer loadCapabilitiesCommon
INFO: OpenGL Renderer Information
 * Vendor: NVIDIA Corporation
 * Renderer: GeForce GT 545/PCIe/SSE2
 * OpenGL Version: 3.2.0 NVIDIA 390.157
 * GLSL Version: 1.50 NVIDIA via Cg compiler
 * Profile: Core
Mar 29, 2024 12:39:28 PM com.jme3.audio.openal.ALAudioRenderer initOpenAL
INFO: Audio Renderer Information
 * Device: OpenAL Soft
 * Vendor: OpenAL Community
 * Renderer: OpenAL Soft
 * Version: 1.1 ALSOFT 1.15.1
 * Supported channels: 64
 * ALC extensions: ALC_ENUMERATE_ALL_EXT ALC_ENUMERATION_EXT ALC_EXT_CAPTURE ALC_EXT_DEDICATED ALC_EXT_disconnect ALC_EXT_EFX ALC_EXT_thread_local_context ALC_SOFT_loopback
 * AL extensions: AL_EXT_ALAW AL_EXT_DOUBLE AL_EXT_EXPONENT_DISTANCE AL_EXT_FLOAT32 AL_EXT_IMA4 AL_EXT_LINEAR_DISTANCE AL_EXT_MCFORMATS AL_EXT_MULAW AL_EXT_MULAW_MCFORMATS AL_EXT_OFFSET AL_EXT_source_distance_model AL_LOKI_quadriphonic AL_SOFT_buffer_samples AL_SOFT_buffer_sub_data AL_SOFTX_deferred_updates AL_SOFT_direct_channels AL_SOFT_loop_points AL_SOFT_source_latency
Mar 29, 2024 12:39:28 PM com.jme3.audio.openal.ALAudioRenderer initOpenAL
WARNING: Pausing audio device not supported.
Mar 29, 2024 12:39:28 PM com.jme3.audio.openal.ALAudioRenderer initOpenAL
INFO: Audio effect extension version: 1.0
Mar 29, 2024 12:39:28 PM com.jme3.audio.openal.ALAudioRenderer initOpenAL
INFO: Audio max auxiliary sends: 4
Mar 29, 2024 12:39:30 PM com.jme3.app.LegacyApplication handleError
SEVERE: Uncaught exception thrown in Thread[jME3 Main,5,main]
java.lang.ArrayIndexOutOfBoundsException: Index 67 out of bounds for length 67
	at com.jme3.anim.SkinningControl.applySkinningTangents(SkinningControl.java:659)
	at com.jme3.anim.SkinningControl.softwareSkinUpdate(SkinningControl.java:453)
	at com.jme3.anim.SkinningControl.controlRenderSoftware(SkinningControl.java:264)
	at com.jme3.anim.SkinningControl.controlRender(SkinningControl.java:304)
	at com.jme3.scene.control.AbstractControl.render(AbstractControl.java:126)
	at com.jme3.scene.Spatial.runControlRender(Spatial.java:763)
	at com.jme3.renderer.RenderManager.renderSubScene(RenderManager.java:809)
	at com.jme3.renderer.RenderManager.renderSubScene(RenderManager.java:819)
	at com.jme3.renderer.RenderManager.renderSubScene(RenderManager.java:819)
	at com.jme3.renderer.RenderManager.renderScene(RenderManager.java:793)
	at com.jme3.renderer.RenderManager.renderViewPort(RenderManager.java:1210)
	at com.jme3.renderer.RenderManager.render(RenderManager.java:1292)
	at com.jme3.app.SimpleApplication.update(SimpleApplication.java:283)
	at com.jme3.system.lwjgl.LwjglAbstractDisplay.runLoop(LwjglAbstractDisplay.java:163)
	at com.jme3.system.lwjgl.LwjglDisplay.runLoop(LwjglDisplay.java:225)
	at com.jme3.system.lwjgl.LwjglAbstractDisplay.run(LwjglAbstractDisplay.java:245)
	at java.base/java.lang.Thread.run(Thread.java:829)

Here's the essence of the test app:

    public void simpleInitApp() {
        Spatial model = assetManager.loadModel("RPM_RandomAvatar.glb");
        rootNode.attachChild(model);

        Spatial child = ((Node) model).getChild(0);
        SkinningControl skinningControl
                = child.getControl(SkinningControl.class);
        skinningControl.setHardwareSkinningPreferred(false);
    }

A runtime check could easily be added to SkinningControl, like so:

                    int index = ib.get(idxWeights++);
                    if (index < 0 || index >= offsetMatrices.length) {
                        continue;
                    }
                    Matrix4f mat = offsetMatrices[index];

However, it would be even better for jme3-plugins to detect the out-of-range bone index while importing the model.

Start with SkinningControl.java, especially applySkinningTangents() and softwareSkinUpdate(), using the reported glTF model and test application to reproduce the out-of-range bone index. Check the jme3-plugins import path for where bone indices are handled. Done means software skinning no longer throws for this model, with invalid indices handled safely or rejected during import.