Problem loading textured model (probably solved)

codex · January 15, 2021, 12:54am

I’ve used Blender v2.79 to make an model and export it as an .obj. It worked just fine until I attempted to texture my model in Blender and got this runtime error:

ClassCastException: com.jme3.asset.ModelKey cannot be cast to com.jme3.asset.TextureKey

Is there a different model format that JME will handle and will handle textures? Or is there a different problem here?

pspeed · January 15, 2021, 3:47am

Did that exception have a stack trace? It’s 99% of the useful information of an exception.

codex · January 15, 2021, 12:34pm

Stack trace:
java.lang.ClassCastException: com.jme3.asset.AssetKey cannot be cast to com.jme3.asset.TextureKey
at com.jme3.texture.Texture.setKey(Texture.java:427)
at com.jme3.scene.plugins.MTLLoader.loadTexture(MTLLoader.java:186)
at com.jme3.scene.plugins.MTLLoader.readLine(MTLLoader.java:232)
at com.jme3.scene.plugins.MTLLoader.load(MTLLoader.java:304)
at com.jme3.asset.DesktopAssetManager.loadLocatedAsset(DesktopAssetManager.java:259)
at com.jme3.asset.DesktopAssetManager.loadAsset(DesktopAssetManager.java:373)
at com.jme3.scene.plugins.OBJLoader.loadMtlLib(OBJLoader.java:336)
at com.jme3.scene.plugins.OBJLoader.readLine(OBJLoader.java:389)
at com.jme3.scene.plugins.OBJLoader.load(OBJLoader.java:578)
at com.jme3.asset.DesktopAssetManager.loadLocatedAsset(DesktopAssetManager.java:259)
at com.jme3.asset.DesktopAssetManager.loadAsset(DesktopAssetManager.java:373)
at com.jme3.asset.DesktopAssetManager.loadModel(DesktopAssetManager.java:416)
at com.jme3.asset.DesktopAssetManager.loadModel(DesktopAssetManager.java:420)
at mygame.Main.initCar(Main.java:76)
at mygame.Main.simpleInitApp(Main.java:60)
at com.jme3.app.SimpleApplication.initialize(SimpleApplication.java:220)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.initInThread(LwjglAbstractDisplay.java:130)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.run(LwjglAbstractDisplay.java:211)
at java.lang.Thread.run(Thread.java:748)

Code:

private void initCar(float x, float y, float z) {
	Spatial car = assetManager.loadModel("Models/vehicle.obj");
	Material mat = new Material(assetManager, "Common/MatDefs/Misc/ShowNormals.j3md");
	player = new Car(x, y, z, car, mat);
	rootNode.attachChild(player.createVehicle());
}

Where I make my spatial is where the error occurs (line 76).

sgold · January 15, 2021, 7:02pm

Looks like Issue 1174.

pspeed · January 15, 2021, 7:10pm

Looks different to me. No “MaterialList” involved in this case:

Seems like Texture is expecting all of its asset keys to be TextureKey… which I don’t think is necessarily a good assumption… but I guess it’s a requirement of Textures since forever.

Also looks like it’s only a problem with older JME versions. Master has this code for MTLLoader.loadTexture:

github.com

jMonkeyEngine/jmonkeyengine/blob/master/jme3-core/src/plugins/java/com/jme3/scene/plugins/MTLLoader.java#L177


      
              matName = name;
          }
          
          protected Texture loadTexture(String path){
              String[] split = path.trim().split("\\p{javaWhitespace}+");
              
              // will crash if path is an empty string
              path = split[split.length-1];
              
              String name = new File(path).getName();
              TextureKey texKey = new TextureKey(folderName + name);
              texKey.setGenerateMips(true);
              Texture texture;
              try {
                  texture = assetManager.loadTexture(texKey);
                  texture.setWrap(WrapMode.Repeat);
              } catch (AssetNotFoundException ex){
                  logger.log(Level.WARNING, "Cannot locate {0} for material {1}", new Object[]{texKey, key});
                  texture = new Texture2D(PlaceholderAssets.getPlaceholderImage(assetManager));
                  texture.setWrap(WrapMode.Repeat);
                  texture.setKey(texKey);

…which is making a TextureKey.

OP, what version of JME are you using?

codex · January 15, 2021, 7:51pm

I’m using JME v3
Edit: looks like v3.2

pspeed · January 15, 2021, 8:50pm

Even still, looks like this error shouldn’t happen.

github.com

jMonkeyEngine/jmonkeyengine/blob/v3.2.0-stable/jme3-core/src/plugins/java/com/jme3/scene/plugins/MTLLoader.java#L186


    TextureKey texKey = new TextureKey(folderName + name);
    texKey.setGenerateMips(true);
    Texture texture;
    try {
        texture = assetManager.loadTexture(texKey);
        texture.setWrap(WrapMode.Repeat);
    } catch (AssetNotFoundException ex){
        logger.log(Level.WARNING, "Cannot locate {0} for material {1}", new Object[]{texKey, key});
        texture = new Texture2D(PlaceholderAssets.getPlaceholderImage(assetManager));
        texture.setWrap(WrapMode.Repeat);
        texture.setKey(key);
    }
    return texture;
}
protected boolean readLine(){
    if (!scan.hasNext()){
        return false;
    }
    String cmd = scan.next().toLowerCase();

…but it’s in the block for missing textures. So maybe if you figure out how to avoid the missing textures then you can work around the issue.

yaRnMcDonuts · January 15, 2021, 8:59pm

codex:

Code:

private void initCar(float x, float y, float z) {
	Spatial car = assetManager.loadModel("Models/vehicle.obj");
	Material mat = new Material(assetManager, "Common/MatDefs/Misc/ShowNormals.j3md");
	player = new Car(x, y, z, car, mat);
	rootNode.attachChild(player.createVehicle());
}

Where I make my spatial is where the error occurs (line 76).

Have you tried loading the model in .j3o format? I was unaware the engine could even load .obj models at run-time and am unsure how reliable it is.

But I would suggest exporting your model from Blender in GLTF format, and then use JME to convert from gltf → j3o; that will be a much more reliable format in a JME app.

codex · January 15, 2021, 10:48pm

Apparently, obj isn’t that reliable with jme.
How do you export from Blender in GLTF? The only export formats I can find are dae, abc, 3ds, fbx, ply, obj, x3d, and stl. I cannot get any of those (except obj, kinda) to work.

mitm · January 15, 2021, 11:09pm

Update your blender version to 2.8+ and the scripts is included. Using gltf with 2.79 requires you install separate scripts and they are loaded with bugs.

If you cant update blender, here are the scripts,

mitm · January 15, 2021, 11:20pm

It has its uses but they are limited.

codex · January 15, 2021, 11:23pm

Is there any other way to export from Blender or convert from [types listed below] to end up with j3o or GITF?

mitm · January 15, 2021, 11:24pm

To use gltf with 2.79, read this,

github.com

KhronosGroup/glTF-Blender-Exporter/blob/master/docs/user.md

User Documentation
------------------

### glTF 2.0 Materials

glTF 2.0 introduced two PBR materials: The Metallic-Roughness and Specular-Glossiness workflow. As the Metallic-Roughness is integrated into core glTF 2.0, details are explained for this workflow. For Specular-Glossiness, it is similar or almost the same.

At point of writing, Blender supports two material settings: One for `Blender Render` and one for `Cycles Render`. Fortunately, the glTF 2.0 Materials can be simulated using the `Cycles Render` by implementing a custom node tree. Advantage is, that the preview of the Cycles output is almost 1:1 to the expected rendering output when using the glTF 2.0 materials.

However, this custom node tree needs to be imported and linked to a Blender file. For the future, it is planned to use the `Eevee` shader node, which will replace the current node group.

For shadeless materials, glTF 2.0 also has an Unlit material extension. Unlit materials use Diffuse or vertex colors as input, and cannot currently be created with Cycles nodes. Materials with the *Shadeless* setting enabled will automatically use the glTF 2.0 Unlit extension.

#### Integrating glTF 2.0 PBR Materials

Following picture shows a basic Blender scene using the Cycles renderer.

![glTF 01 Blender Scene](glTF_01_Blender_Scene.png)

If this scene would be exported, the perspective camera and Suzanne are written to the glTF 2.0 file. However, this scene would not contain any materials. As this glTF 2.0 file is valid, any glTF 2.0 render would use a default material.

This file has been truncated. show original

mitm · January 15, 2021, 11:27pm

You can install an ogre scripts into 2.79,

This is also a legacy format that will go away one day and it also does not work with blender 2.8.

mitm · January 15, 2021, 11:30pm

If you use sdk 3.2, ogre still works with that just fine, sdk 3.3 uses the new animation system by default and you will run into more trouble as it is not in the wiki yet. The info is available by forum searches though.

Edit:
I added another link for gltf documentation above. It goes into depth on blender and gltf and 2.79.

Edit:
You can try fbx but you may or may not hit problems there. I have not used it much.

Ali_RS · January 16, 2021, 5:44am

@codex you can also use an online obj → gltf converter

codex · January 16, 2021, 1:00pm

That might be best for me.
Are there any that your recommend?

Ali_RS · January 16, 2021, 2:31pm

Have tried it only for FBX to GLTF (it only export as GLB which is the GLTF binary format) but should work for OBJ as well.
Also, you can find more by a google search.

codex · January 16, 2021, 2:34pm

I can do fbx from Blender.
Thanks!

Ali_RS · January 16, 2021, 2:39pm

You are welcome.

Note, just took a look and it does already support OBJ.