Raster to mesh

[saberraz]

Feature description

It would be good to have a native QGIS tool under processing to convert Raster to Mesh. See details here: https://lists.osgeo.org/pipermail/qgis-developer/2023-March/065630.html

Additional context

No response

[kannes]

As pointed out by Jean-Baptiste Peter in https://lists.osgeo.org/pipermail/qgis-developer/2023-March/065636.html, different algorithms can create vastly different triangles.

It would be great to have both a "dump" algorithm that simply meshes the terrain in lots of squares of two triangles each (like e.g. Qgis2threejs does it) and a one that creates triangles as actually needed to represent the raster's surface in a more natural way, building an optimal topology with fewer triangles.

Additionally, being able to define breaklines would be a very nice feature.

[wonder-sk]

It would be great to have both a "dump" algorithm that simply meshes the terrain in lots of squares of two triangles each

QGIS 3D internally does exactly that - from a DEM it creates squares of two triangles each, without any further optimizations.

The whole thing is maybe a bit more complicated - once we have a mesh, what are we going to do with it? If it is a large mesh from a big DEM raster, it is impractical to load it at once in a 3D view - it would take both a lot of GPU memory and the rendering would be slow. So in the end one would typically want to use some "level of detail" approach - using a tiling scheme like with XYZ tiles, to make it possible to show detailed mesh from close up and approximate mesh when looking from distance. But that also brings us to more complications :slightly_smiling_face: - e.g. how to make sure the mesh is always watertight (with no holes on edges), or how to store such tiled mesh data (e.g. 3D tiles?)

[nyalldawson]

Could https://github.com/OpenDroneMap/dem2mesh be of use here?

[kannes]

More potential candidates from my bookmarks:

• https://github.com/fogleman/hmm
• https://github.com/geo-data/cesium-terrain-builder
• https://github.com/heremaps/tin-terrain
• https://github.com/kylebarron/pymartini

[Jean-Roc]

I'm adding two others repositories of kyle baron

• https://github.com/kylebarron/pydelatin which is a wrapper of hmm
• https://github.com/kylebarron/quantized-mesh-encoder, it takes the output of pydelatin or pymartini and encode it to quantized-mesh-1.0 format (a multi-resolution quadtree pyramid of meshes, format created by cesium)