How to load gltf model correctly?

joejoe2 · September 30, 2021, 5:54am

hi, I am trying to load gltf model by

Spatial model = assetManager.loadModel(“Models/gltf/rocket/scene.gltf”);

but it fails with

com.jme3.asset.AssetLoadException: An error occurred loading Models/gltf/rocket/scene.gltf
at com.jme3.scene.plugins.gltf.GltfLoader.loadFromStream(GltfLoader.java:181)
at com.jme3.scene.plugins.gltf.GltfLoader.load(GltfLoader.java:106)
at com.jme3.asset.DesktopAssetManager.loadLocatedAsset(DesktopAssetManager.java:272)
at com.jme3.asset.DesktopAssetManager.loadAsset(DesktopAssetManager.java:388)
at com.jme3.asset.DesktopAssetManager.loadModel(DesktopAssetManager.java:439)
at com.jme3.asset.DesktopAssetManager.loadModel(DesktopAssetManager.java:444)
at com.joejoe2.glass.HelloJME.simpleInitApp(HelloJME.java:64)
at com.jme3.app.SimpleApplication.initialize(SimpleApplication.java:240)
at com.joejoe2.glass.MyAndroidHarnessFragment.initialize(MyAndroidHarnessFragment.java:529)
at com.jme3.system.android.OGLESContext.onDrawFrame(OGLESContext.java:342)
at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1591)
at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1286)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method ‘com.jme3.scene.Node com.jme3.scene.Spatial.getParent()’ on a null object reference
at com.jme3.anim.SkinningControl.getAttachmentsNode(SkinningControl.java:403)
at com.jme3.scene.plugins.gltf.GltfLoader.setupControls(GltfLoader.java:1151)
at com.jme3.scene.plugins.gltf.GltfLoader.loadFromStream(GltfLoader.java:166)

the model is downloaded from here

But I can load glb model in this way directly, is this the right way to load gltf model ?

sgold · September 30, 2021, 8:43am

I think you’re on the right track. Apparently there’s a bug in JMonkeyEngine’s glTF loader. I’m investigating.

joejoe2 · September 30, 2021, 9:20am

I also found that an glb model size=16mb will throw the out of memory error on my device (Android). Is there any method to increase the heap size or reduce the quality wile loading ? because I can load it on SceneForm library, but i do not know how it works

sgold · September 30, 2021, 9:26am

You shouldn’t be loading a glTF model on a device with small memory. Instead, you should convert the model to J3O format (on a build system with plenty of memory), install the J3O on the target device, and load that instead.

sgold · September 30, 2021, 9:55am

I made some progress and opened an issue for the bug:

github.com/jMonkeyEngine/jmonkeyengine

NPE while loading glTF model "Hover bike - "The Rocket"

opened 09:54AM - 30 Sep 21 UTC

stephengold

To reproduce the issue; 1. download the Autoconverted format glTF from https:…//sketchfab.com/3d-models/hover-bike-the-rocket-8b2e5bfca78e41c791b4e5b5e8c04512 2. unzip the files into "jme3-examples/src/main/resources" 3. add `assetManager.loadModel("scene.gltf");` to the example app of your choice Typical stack trace: ```text com.jme3.asset.AssetLoadException: An error occurred loading scene.gltf at com.jme3.scene.plugins.gltf.GltfLoader.loadFromStream(GltfLoader.java:181) at com.jme3.scene.plugins.gltf.GltfLoader.load(GltfLoader.java:106) at com.jme3.asset.DesktopAssetManager.loadLocatedAsset(DesktopAssetManager.java:272) at com.jme3.asset.DesktopAssetManager.loadAsset(DesktopAssetManager.java:388) at com.jme3.asset.DesktopAssetManager.loadModel(DesktopAssetManager.java:439) at com.jme3.asset.DesktopAssetManager.loadModel(DesktopAssetManager.java:444) ... Caused by: java.lang.NullPointerException at com.jme3.anim.SkinningControl.getAttachmentsNode(SkinningControl.java:403) at com.jme3.scene.plugins.gltf.GltfLoader.setupControls(GltfLoader.java:1151) at com.jme3.scene.plugins.gltf.GltfLoader.loadFromStream(GltfLoader.java:166) ... 10 more ``` No matter how corrupt the model is, the loader shouldn't throw an NPE! Forum discussion at https://hub.jmonkeyengine.org/t/how-to-load-gltf-model-correctly/44946 For reasons I don't yet understand, the loader isn't finding anywhere to add the `SkinningControl`. The following workaround allows the model to load, but probably isn't the best solution: ```patch # This patch file was generated by NetBeans IDE # It uses platform neutral UTF-8 encoding and \n newlines. --- a/jme3-plugins/src/gltf/java/com/jme3/scene/plugins/gltf/GltfLoader.java +++ b/jme3-plugins/src/gltf/java/com/jme3/scene/plugins/gltf/GltfLoader.java @@ -1148,7 +1148,11 @@ continue; } SkinData skinData = fetchFromCache("skins", bw.skinIndex, SkinData.class); - skinData.skinningControl.getAttachmentsNode(bw.joint.getName()).attachChild(bw.attachedSpatial); + SkinningControl control = skinData.skinningControl; + if (control.getSpatial() == null) { + rootNode.addControl(control); + } + control.getAttachmentsNode(bw.joint.getName()).attachChild(bw.attachedSpatial); } } ```

joejoe2 · September 30, 2021, 3:16pm

Another question, I wonder that if i have multiple material with this gltf, how can i decide the loader to load specific materail ? And the lights defined in gltf/glb seems to not work, i have to set directional light everytime.

pspeed · September 30, 2021, 5:49pm

The “material” is in the gltf file. Did you mean textures? The gltf already refers to the textures.

sgold · September 30, 2021, 6:57pm

Do you appreciate the effort I put into trying to help you? If so, it would be courteous to say “thank you” or to click on the heart-shaped icon under my post.