Removal of Tangents code?

[mrdoob]

Now that bump/normalmaps are using derivatives I wonder if we need the tangents code (Geometry.computeTangents and BufferGeometry.computeTangents) any longer.

These are the only examples that rely on it:

webgl_materials_normaldisplacementmap
Uses NormalDisplacementShader.js, which I don't know if we should still maintain

webgl_materials_bumpmap_skin
I think it's not needed on this one, but it's currently broken

webgl_terrain_dynamic
easy to port to derivatives I think

Does anyone rely on this code? And if so, what's the use case?

[bhouston]

Clara.io uses the tangents, although I had to modify them a bit. I use then to do anisotropic (non-circular) highlights:

https://clara.io/view/4faca36d-d9aa-4b1b-b9a2-dfa8d6bc978b

Details: https://en.wikipedia.org/wiki/Specular_highlight#Ward_anisotropic_distribution

I did try to implement anisotropic reflection without tangents but I could never get great results. Now I am not 100% sure I can not get the same results with just UV derivatives, but I couldn't manage it and I tried a fair bit.

The main issue I believe I ran into is that the UV derivatives are constant within a face and change abrutly when you switch to a difference face -- because they are derived from the UV interpolation across each face. Tangents are interpolated from the vertices, thus they vary smoothly across faces, thus you can get continuous results across faces.

You do not notice the abrupt change of UV derivates with bump and normal map because you are not looking at the tangent/binormal directly as you are with an anisotropic highlight, rather just the normal.

/ping @WestLangley: Your math expertise may be useful here.

[mrdoob]

I assume you're using BufferGeometry and custom shaders for that, right? I guess you could then move the tangents generation code to the app level instead?

I'm just trying to simplify/reduce the code we have to maintain.

[bhouston]

I am fine removing it from core.

Actually we did end up are generating tangents explicitly within Clara.io and storing them in our mesh data files, very similar to how explicit UV maps are handled. So we are already doing a fully out of ThreeJS core solution for tangents, although it is based on the tangent code in ThreeJS -- so thank you!

[mrdoob]

Ended up moving BufferGeometry.computeTangents() to BufferGeometryUtils.computeTangents() in examples/js.

[mrdoob]

Aaaand... we're back at 99kb gzipped 😁

[WestLangley]

Yikes!

I agree that tangent computation should be at the application/modeling level. Moving computeTangents() to the examples was the right thing to do.

It was also OK to remove from the library and examples the shaders that rely on attribute tangents.

But you also removed all tangent support from the library. I would not do that.

I would continue to support users who have attribute tangents in their geometry.

[mrdoob]

Oh, I left one. webgl_terrain_dynamic still uses tangents (uses THREE.BufferGeometryUtils.computeTangents()). I'm not sure what to do with webgl_materials_skin though...

[mrdoob]

In the IRC someone is saying that they were relying on NormalDisplacementShader.js. I'll try to bring it back use in a BufferGeometry based example.

[WestLangley]

As I said

But you also removed all tangent support from the library. I would not do that.

I would continue to support users who have attribute tangents in their geometry.

I would suggest we add vertex texture and displacement map support to MeshPhongMaterial instead of restoring the NormalDisplacementShader.

Do any vertex texture examples remain?

[mrdoob]

I would suggest we add vertex texture and displacement map support to MeshPhongMaterial instead of restoring the NormalDisplacementShader.

That sounds good to me!

Do any vertex texture examples remain?

Hmm... webgl_kinect?

[mrdoob]

As per things to keep... Maybe we can keep VertexTangentsHelper, but only for BufferGeometry.

[WestLangley]

It would seem to me that any loader that supports tangents should continue to do so.

Also, the pipeline from Geometry -> DirectGeometry -> BufferGeometry should support tangents.

IMO, those two are important.

You can move the VertexTangentsHelper to the examples if you want.