Vertex colors not loaded in Gltf models

Models coloured through vertex colours are not properly rendered in the application; various attempts in altering the formats and materials have resulted in null results. If a material isn't specified, the model is wholly white. Using the lighting material, even with "UseVertexColor" it's wholly black without details.

The following code is without utilizing any material, but it may be altered to set the 'Lighting.j3md' material. "UseVertexColor" does not appear to function as intended.

Light directionalLight = new DirectionalLight(new Vector3f(-10, -5, -10));
Light ambientLight = new AmbientLight();
Material material = new Material(assetManager, "Common/MatDefs/Light/Lighting.j3md");
material.setBoolean("UseVertexColor", true);
Spatial playerModel = assetManager.loadModel("models/TestGirl.glb");
playerModel.setLocalScale(0.5f);
playerModel.setLocalTranslation(new Vector3f(-4,-7.1f,0));

rootNode.attachChild(playerModel);
rootNode.addLight(directionalLight);
rootNode.addLight(ambientLight);

The model file is available here, for testing:
TestModel.zip

[zzuegg]

at least with prb material you have to set BaseColor to vec4(1,1,1,1) if you want vertex color only.

not at the pc so i cant test. looked at the shader code

//add: seems should be 1,1,1,1 by default.

[Ali-RS]

I can confirm it is not working.

Tried it with Unsahded, Lighting and PBRLighting materials but could not get vertex colors to work in any of them. I can confirm mesh has a color buffer on it. VertexBuffer[fmt=Float, type=Color, usage=Dynamic, elements=7268]

for unshaded material I used

Material mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md" );
mat.setBoolean("VertexColor", true);
mat.setColor("Color", ColorRGBA.White);

for lighting material I used:

Material mat = new Material(assetManager, Materials.LIGHTING);
mat.setFloat("Shininess", 64f);
mat.setBoolean("UseVertexColor", true);
mat.setBoolean("UseMaterialColors", true);
mat.setColor("Ambient", ColorRGBA.White);
mat.setColor("Diffuse", ColorRGBA.White);
mat.setColor("Specular", ColorRGBA.White);
mat.setBoolean("VertexLighting", true);

[pspeed42]

GLTF issues aside, I can assure you 100% that vertex colors work in the engine, definitely for Unshaded.j3md because I use that one all the time (unless it was broken very recently). So to whomever is looking at this, it would be worth checking what's in the color buffer.

What's a colour buffer, and where would I find 'Unshaded.j3md'?

[Ali-RS]

it would be worth checking what's in the color buffer.

Yeah, looks like buffer is corrupted. All of them are set to:

Color[-0.0017700465, 0.0012359808, 0.0018616007, 1.2207218E-4]

The gltf file can be viewed correctly without error on online viewers, so probably an issue with GltfLoader!

[Ali-RS]

I figured this change in gltf blender addon broked GltfLoader.

KhronosGroup/glTF-Blender-IO#1169

If I revert that change I can successfully load vertex colors in JME.

[pspeed42]

Lovely. Is there something in the GLTF that indicates the bad version versus the good version? Or are we stuck having to do some odd detection to find these cases?

Either way, nice of them to break this for everyone. (Or maybe JME is reading these values in a dumb way. 50/50 chance.)

[Ali-RS]

Well, I guess it is detectable based on buffer type.

In the old one, the vertex data was exported as a float buffer

        {
            "bufferView" : 3,
            "componentType" : 5126,
            "count" : 24,
            "type" : "VEC4"
        },

jmonkeyengine/jme3-plugins/src/gltf/java/com/jme3/scene/plugins/gltf/GltfUtils.java

Lines 98 to 99 in a2d639c

	case 5126:
	return VertexBuffer.Format.Float;

after the change, it is now exported as unsigned short buffer

        {
            "bufferView" : 3,
            "componentType" : 5123,
            "count" : 24,
            "normalized" : true,
            "type" : "VEC4"
        },

jmonkeyengine/jme3-plugins/src/gltf/java/com/jme3/scene/plugins/gltf/GltfUtils.java

Lines 94 to 95 in a2d639c

	case 5123:
	return VertexBuffer.Format.UnsignedShort;

there is already a check in GltfLoader to unpack short back to a float buffer but it seems something goes wrong down the road.

jmonkeyengine/jme3-plugins/src/gltf/java/com/jme3/scene/plugins/gltf/GltfLoader.java

Lines 1293 to 1298 in a2d639c

	if (normalized) {
	// Some float data can be packed into short buffers,
	// "normalized" means they have to be unpacked.
	// In that case the buffer is a FloatBuffer
	format = VertexBuffer.Format.Float;
	}

[tonihele]

I got this fixed, I'll submit a PR shortly.

[pspeed42]

re: "Or maybe JME is reading these values in a dumb way. 50/50 chance."
...turns out I was 50/50 right. :)

Edit: (and seems like it was probably a copy-pasta issue.)