refactor mesh_plot around mesh3d

[mdsumner]

See start at 6e0e215

• [ ] make mesh_plot.mesh3d the base functionality
• [ ] what about the quadmesh(, z = ) behaviour? (maybe deprecate in favour of copy_down)
• [ ] allow textures, but remove raster functions
• [ ] use coercions to mesh3d for matrix, raster, stars, silicate, sf, etc
• [ ] figure out where these coercions live, currently most are in anglr, but also quadmesh and sc_triangle (can we have a mesh3d package without importing spatial-spaghetti or rgl?)
• [ ] colouring is always face-wise, so detect vertex/legacy colouring in rgl and convert + warn
• [ ] alllow colours that are on the mesh already, unless overridden -if not present scale from vb[3, ]

[mdsumner]

Also see https://github.com/hypertidy/quadmesh/issues/36

for value lookup via indexing only

[mdsumner]

• matrix as base input
• raster is next (matrix is 0,nrow,0,ncol
• TRI, and QUAD

A problem is that we need as.mesh3d to be able to apply quad, triangle, and discrete versions of those - but only for stars, raster, matrix. So, as.mesh3d really needs a type, and maybe it's not the right function

[mdsumner]

And #37

[mdsumner]

mesh_plot.mesh3d

• [x] define method
• [x] include .default method with as.mesh3d(x, )
• [x] prefer_quad arg
• [x] use material$color if present, then zlim and col args
• [ ] establish behaviours of quadmesh(BasicRaster) in light of reproj, then:
• [ ] refactor .BasicRaster
• [ ] refactor .quadmesh
• [ ] refactor .stars
• [ ] refactor TRI into .sc methods
• [ ] ~crs arg~ consider crazy idea below
• [ ] ~coords arg~ ditto

[mdsumner]

Crazy idea: consider copy_down() for a 2 or 3 layer raster, for 2 you copy onto x, y for 3, copy onto x, y, z - for 1, same as anglr::copy_down(x, raster) now. The lookup is the vertices of x[x, y] in each case. Then we could push coords from mesh_plot, and maybe just enforce the need to reproj(x) instead of allowing crs = .

[mdsumner]

Also, mesh_plot belongs in anglr. It would export mesh_plot, and the attendant 'as.mesh3d' methods for quadmesh. (Or just remove from quadmesh and point to anglr anyway).

Then as.mesh3d() should get all the coords, crs, copy_down stuff - or we add that to the TRI/DEL/QUAD constructors?