DecalGeometry: Transform normal with normal matrix

[WestLangley]

transformDirection() should not be applied to normal vectors, unless under certain conditions. The normal map should be applied, instead.

[WestLangley]

Related: Is there a reason decals are added to the scene in webgl_decals.html, instead of to the mesh to which they are applied?

Currently, if the mesh is rotated, the decals do not.

[Mugen87]

In webgl_decals, transformDirection() is also used in checkIntersection() to transform normals. Does it make sense to update this code as well?

three.js/examples/webgl_decals.html

Line 191 in 19e79dc

n.transformDirection( mesh.matrixWorld );

[Mugen87]

Is there a reason decals are added to the scene in webgl_decals.html, instead of to the mesh to which they are applied?

Not that I am aware of. It would seem more natural to add the decals to the logical parent object.

[WestLangley]

@Mugen87 Doing mesh.attach( decal ) instead of scene.add( decal ) works well, although .attach() only supports a uniformly-scaled parent mesh (the case here). Do you think such a change to the example is worth it?

[Mugen87]

Yes, using attach() looks like a nicer workflow.