FBXLoader: Partial transparent maps doesn't work

[cnspaha]

Description of the problem

When loading a FBX file ( succubus.zip, it is the original file, no export ) via FBXLoader transparent parts of a map isn't taken into account.

The map, opened in Gimp so you can see the transparent parts, hair + feathers:

What it should look like Sketchfab

What it really looks like (my viewer):

The problem can be worked around with when applying following code on every mesh the FBXLoader creates:

            ((obj as THREE.Mesh).material as THREE.Material).transparent = true;
            ((obj as THREE.Mesh).material as THREE.Material).side = THREE.DoubleSide;
            ((obj as THREE.Mesh).material as THREE.Material).alphaTest = 0.5;

But of course I don't want this code to be applied on every mesh because AFAIK transparency and alpha testing costs quite a bit of performance, especially if it isn't needed...

I am willingly to make a PR if I would know how to fix this.

One possible solution is that we would have to check ONLY the PART of the image being used per mesh if there is any transparency and if there is some then setting the transparent parameter on the material.

@Kyle-Larson @takahirox since you both wrote this Loader, do you have any idea?
@Mugen87 @donmccurdy you both are pretty active on loader issues/PRs probably you could help here too? ;)

Three.js version

• [ x ] r88

Browser

• All of them

OS

• All of them

[donmccurdy]

Since the model is on Sketchfab already, you can download the glTF version there. It looks correct with r88 GLTFLoader, other than some transparency artifacts that aren't loader-related.

Preview on https://gltf-viewer.donmccurdy.com/:

Issue in the FBX file looks similar to #11598

[WestLangley]

If you are setting alphaTest, and your textures are cut-outs (no semi-transparency), there is no need to set material.transparent = true. And therefore, you should see no "transparency artifacts".

[donmccurdy]

That's good to know, thanks 🙂

the glTF asset from sketchfab doesn't set alphaTest but perhaps it should... trying a quick test after dragging the glTF into https://gltf-viewer.donmccurdy.com/ ...

content.traverse((node) => {
  if (node.isMesh) {
    node.material.transparent = false;
    node.material.alphaTest = 0.5;
  }
});

i'm not getting the right result:

[Mugen87]

If a load the FBX file with FBXLoader and set alphaTest to 0.5, the result looks okay.

Uploading the FBX file back to Sketchfab, i have the following result. It looks like that manual adjustments by the user are also necessary when using Sketchfab.

[Mugen87]

I guess we can close this issue.

[cnspaha]

If a load the FBX file with FBXLoader and set alphaTest to 0.5, the result looks okay.

can you provide me with your example code?
Because in my case it looks quite different... got some nasty white silhuettes around the feathers but don't know why.
I set the side to DoubleSide and the alphaTest to 0.5, don't do anything more with the material.

If you are setting alphaTest, and your textures are cut-outs (no semi-transparency), there is no need to set material.transparent = true. And therefore, you should see no "transparency artifacts".

Thanks :)

So the only option is to set alphaTest to 0.5 for every model and part I load? Because there is no possibility to check if I need to?

[donmccurdy]

So the only option is to set alphaTest to 0.5 for every model and part I load? Because there is no possibility to check if I need to?

GLTFLoader could be altered to do this automatically, assuming it shows the right result (currently it isn't for me; see above). Not sure whether the FBX format provides clear indicators of when alphaTest should be changed or not though, to enable FBXLoader to do it automatically.

[cnspaha]

GLTFLoader could be altered to do this automatically, see above, assuming it shows the right result (currently it isn't for me). Not sure whether the FBX format provides clear indicators of when alphaTest should be changed or not though, to enable FBXLoader to do it automatically.

haven't used the GLTFLoader yet.
Regarding the indicator for alpha in the FBX format I will do some researching, but don't know if it will provide good results :/ But when I do, I will post in this issue and let you know

[Mugen87]

@cnspaha I've just done this:

loader.load( 'models/fbx/succubus.fbx', function( object ) {

	object.traverse( function( o ) {

		if ( o.isMesh === true ) {

			o.material.alphaTest = 0.5;
		
		}

	} );
           
	scene.add( object );

} );

[cnspaha]

@Mugen87
I do the same as you. But just found the culprit... it is the "alpha" property on the WebGLRenderer.
If it is set to "true" the white silhuette appears...

[cnspaha]

close this, since it doesn't seem possible to check if there such parts contains alpha.

[donmccurdy]

I followed up about why the glTF version doesn't render correctly; there is an unexpected case in the format spec. Will post more updates here: KhronosGroup/glTF#1158

[looeee]

GLTFLoader could be altered to do this automatically, assuming it shows the right result (currently it isn't for me; see above). Not sure whether the FBX format provides clear indicators of when alphaTest should be changed or not though, to enable FBXLoader to do it automatically.

@donmccurdy how is this indicated in GLTF? I'll take a look and see if there is anything similar in FBX.

[donmccurdy]

@looeee glTF sets alphaMode as one of BLEND, MASK, or OPAQUE. Another property, alphaCutoff, corresponds to three.js's alphaTest. But (per KhronosGroup/glTF#1158) alphaCutoff is only used in MASK mode, not BLEND, and so the format technically does not allow what Sketchfab is trying to do here. That may be an oversight that needs to be corrected in a future glTF version...

https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#alpha-coverage

[looeee]

There's an enum AlphaSource in FBX, unfortunately the documentation is as usual pretty sparse (documentation as comments here):

{ 
    eNone, // no alpha         
    eRGBIntensity,  //RGB Intensity (computed).
    eBlack // Alpha channel. Black is 100% transparency, white is opaque          
};

I wonder if eBlack could be used to indicate alpha test is needed?

EDIT: tested with a few models including this one, and I can't find any where this enum is actually set... so I guess we are stuck with doing it manually.

[yazancash]

i have same problem.
in FBX file, textures are defined as below:

Texture: 123, "Texture::texmap123", "" {
	Type: "TextureVideoClip"
	Version: 202
	TextureName: "Texture::texmap123"
	Properties70:  {
		P: "UseMaterial", "bool", "", "",1
	}
	FileName: "123.png"
	ModelUVTranslation: 0,0
	ModelUVScaling: 1,1
	Texture_Alpha_Source: "RGBIntensity"
	Cropping: 0,0,0,0
}

i can see Texture_Alpha_Source: "RGBIntensity"
but model is appearing with no transparency. even when i set AlphaTest = 0.5

is there any solution for this?