Support raster overlays with an arbitrary projection

[kring]

Using PROJ or something, probably.

We will need to wait until the geometry is loaded, compute the bounds of all vertices in the projected coordinate system, and then select the raster overlay tiles with the appropriate LOD to cover all the vertices.

[lilleyse]

@kring I've been thinking about this as well for OWT. Do you have a sense whether this would be implemented by reprojecting the imagery to geographic or by projecting the mesh's texture coordinates?

[kring]

My current thinking is to generate a set of texture coordinates per projection, because:

• It's hard to reproject the imagery without losing quality.
• It'll be unusual (I think) for overlays with more than 1-2 different projections to be attached to a single tileset, so the texture coordinates won't get prohibitive.