Proposal for fixing tile boundary continuity issues

[morishuz]

I propose a new way to generate mesh tiles. Rather than having overlapping regions and cropping them to size, we should generate meshes from raster tiles that do not overlap (faster, simpler). then in a second step we insert points between the two tiles, at regular intervals at a sub pixel position, and add them to both of the adjacent meshes. These would be overlapping vertices, with identical height and position in both adjacent tiles. This guarantees continuity of the mesh and is simple to implement. The only slight drawback would be the need to update the edges in the mesh in a second step.

1. generate TIN mesh for each raster tile separately and independently
   

2. place vertices on midpoint between tiles. the height for each vertex is computed directly from the raster values (average between two cells etc). the vertices shown here in red are for the boundary between blue and green tiles. obviously this needs to be repeated for all boundaries between all tiles
   

3. update edges for each mesh to accommodate new vertices.
   

[pksorensen]

Sounds like a good plan :) Would allow to create a larger dataset in map/reduce style.

One note here, do consider to make this 2/3 calls on CLI such it can be parallelized accross nodes also.

1. Call CLI for each raster tile (cold be 16384 x 16384 raster tiles) and it generate a output folder per file
2. When done for all, call Cli again to merge all (or see 3))
3. Optional. Be able to merge over multiple nodes also. (not as improtant, but idea would be to merge 4 tiles recursive until at top.

[delfrrr]

@pksorensen I guess now it's easier to parallelize as tiles are generated independently; you can split input raisers and processing them independently;

Merging tile sets can be interesting feature 👍