cell corners

[mdsumner]

need functions for raster vertexIndex_FromCell, or

ll_FromCell(raster, cells) 
lr_FromCell/tl_FromCell/tr_FromCell

where the four indices are implicit on the transform, and sparsely generated only for populated cells. Then generalize for L3bin, to tie together tabularaster and quadmesh.

Does this work by

• translating centre cell index to ll/lr/tl/tr index
• then just doing mod and %/% x, y to get the values

So the full set of coords is never generated, maybe never generated until transformed or visualized by rgl?

[mdsumner]

this will be a silicate method