Bad Texture Unit-scale, missing Transparency and Metal for Fusion360 Materials

[wallabyway]

Markers:

• Red: Fabric has the wrong texture scale
• Green: Transparent fabric is not working (using alpha cut-through mask)
• Blue: Metalic materiał comes out black, maybe scale issue?

Right: Fusion(F3D) in LMV Left: LGLTracer with glTF

Source F3D: https://developer.api.autodesk.com/oss/v2/signedresources/8982cad5-0eda-4beb-96fb-6244062d21aa?region=US

[wallabyway]

Missing Metals

The metal issue is related to using the wrong materials json file.

The Materials.json.gz file maps the f0 base color into the specular value, but the metallic-roughness value is gone. The ProteinMaterials.json.gz file contains both the f0 base color of metals, as well as it's metallic roughness. The ProteinMaterials.json.gz has more information needed for glTF's PBR materials, than Materials.json.gz. You may want to switch over to that. Note: fixing metals will also fix this issue... https://github.com/petrbroz/forge-convert-utils/issues/23

Texture Scale

Looks like LGLTracer is missing support for KHR_texture_transform, causing the texture scale issue. Nothing to do with forge-convert-utils. https://github.com/LGL-Tracer-Renderer/LGL-Tracer-Renderer.github.io/issues/15

[wallabyway]

The fix:

divide glossiness by 20 and by 60, depending on isMetal, like so...

at line 126 in reader.ts

            roughness: _mat?.glossiness ? ( 20.0/ _mat.glossiness ) : 1.0, // TODO: how to map glossiness to roughness properly?
            scale: {x: _mat?.maps?.diffuse?.scale.texture_UScale ?? 1.0 , y: _mat?.maps?.diffuse?.scale.texture_VScale ?? 1.0}
        };
        if (_mat?.diffuse) {
            mat.diffuse.x = _mat.diffuse[0];
            mat.diffuse.y = _mat.diffuse[1];
            mat.diffuse.z = _mat.diffuse[2];
        }
        if (_mat?.metal && _mat.specular && _mat.glossiness) {
            mat.diffuse.x = _mat.specular[0];
            mat.diffuse.y = _mat.specular[1];
            mat.diffuse.z = _mat.specular[2];
            mat.roughness = 60/_mat.glossiness;
        }        

Reference (LMV)

Results ( Three.js, Babylon.js, LGLTracer ):

[petrbroz]

Thanks @wallabyway, I've just merged the PR. Next week we can test it out and publish a new version if everything looks correct.