Remove SphericalReflectionMapping

[WestLangley]

As discussed here, sphere maps are camera view-dependent and are not appropriate as we are using them. Furthermore, SEMs assume the object is centered directly in front of the camera, which is generally not the case in three.js.

Users can use MeshMatcapMaterial instead. I have seen users use SphericalReflectionMapping, but they are passing in a matcap texture, thinking it is the same thing. A spherical reflection map is not the same as a matcap.

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@mrdoob I am not sure about the change I made to Sidebar.Material.js...

@takahirox I was also not sure what to do with MMDLoader.js. MeshToonMaterial no longer extends MeshPhongMaterial (#18003), and no longer supports environment maps, so I was not sure what changes would be appropriate to MMDLoader.js. That loader is not modified in this PR. Can you please have a look? We can safely save it for later.

To do: update migration docs when appropriate.

[mrdoob]

@mrdoob I am not sure about the change I made to Sidebar.Material.js...

I think this works.

But when removing EquirectangularReflectionMapping we may want to do a THREE.EquirectangularTexture that tells the renderer that needs to be internally converted to a CubeTexture at upload time.

What do you think?

[mrdoob]

Thanks!

[WestLangley]

I'll give it a try and see how it goes...

[takahirox]

@WestLangley Sorry I didn't notice for a while. I reviewed MMD specification and found that material in MMD can apply environment mapping while it is cartoon based material. So the current MeshToonMaterial doesn't satisfy MMD material specification. I think I need to implement MMD specific material MMDToonMaterial in MMDLoader by extending MeshToonMaterial (or MeshPhongMaterial) or using ShaderMaterial. If node based material system lands, it would be a good use case.