Rasputin

Rasputin turns a digital elevation model (DEM) into a triangulated irregular network (TIN): a triangle mesh of the terrain that uses few triangles where the ground is smooth and many where it is rough, and never strays from the DEM by more than a height tolerance you choose.

The Bygdin catchment (305 km²) at a 10 m tolerance, each triangle coloured by its CORINE land-cover class. Elevation © Kartverket (CC BY 4.0); land cover © European Union, Copernicus Land Monitoring Service 2018, EEA. How it was made: docs/benchmarks/2026-09-29/bygdin-landcover.md.

What it does

• DEM in, mesh out. One GeoTIFF, several, or a directory of tiles (Kartverket's DTM10, for example), stitched into one grid.
• A domain. Mesh only the inside of a polygon, such as a catchment (GeoJSON or WKT, in any CRS that pyproj reads).
• Features as constraints. Lakes, land-cover borders, roads and rivers (GeoJSON, GeoPackage or GML) become edges of the mesh, so no triangle crosses them.
• Land-cover labels. With a CORINE class map, every triangle gets the class of the polygon it lies in.
• Refinement to a tolerance. Triangles are split at the worst DEM point until every triangle is within --tolerance metres of the DEM, then kept Delaunay, with a minimum-angle start so there are no slivers along the boundary.
• Auto-catchment. rasputin catchment computes the catchment of a lake from the DEM (a --seed point in the lake) and writes it as a GeoJSON polygon, reduced to --outline-tolerance with its area kept, ready for --domain.

Quick example

Install first (INSTALL.md); the example needs the codecs extra, because the committed DEM tile is LZW-compressed. The install is bounds-checked by default; INSTALL.md's "Bounds checks" section says how to build an unchecked copy for heavy runs. From the repository root:

# A 50 km DTM10 tile, meshed inside a quarter disc of radius 30 km,
# to within 1 m of the DEM.
rasputin mesh \
    --dem tests/fixtures/dem_archive/7908_3_10m_z33.tif \
    --domain docs/benchmarks/2026-09-26/quarter.geojson \
    --tolerance 1 \
    --out quarter.vtk

# The same, with CORINE land cover as constraints and labels,
# at a 5 m tolerance.
rasputin mesh \
    --dem tests/fixtures/dem_archive/7908_3_10m_z33.tif \
    --domain docs/benchmarks/2026-09-26/quarter.geojson \
    --features tests/fixtures/corine/clc2018_7908_3.gpkg --features-map corine \
    --tolerance 5 \
    --out quarter_landcover.vtk

# Natural colours for the land-cover classes, for ParaView.
rasputin palette corine --out corine.json

The first command writes about 430,000 triangles in under two seconds on a laptop (Apple M1 Max). Add --stats - to print sizes, mesh quality and timings.

rasputin --help lists the commands, and rasputin mesh --help explains every option.

Output and viewing

• .vtk (legacy VTK, one file) is for ParaView. It holds the triangles, the constraint edges with their feature bits and, with a class map, the cell array land_cover_code. To colour by land cover, import corine.json in ParaView's Colour Map Editor (Choose Preset, Import) and colour by land_cover_code.
• .ply is for QGIS and other mesh tools. The surface goes to --out, and the constraint edges, if you want them, to a second file named by --out-edges.

Both formats are binary by default; --ascii writes text you can read with head.

How it is built

• A C++20 core (include/terrain/, src/): exact geometric predicates, a constrained Delaunay triangulation, a noder that makes input lines meet cleanly, and the parallel refinement. The core never opens a file and knows nothing about coordinate systems. The only third-party C++ code is detria, vendored in lib/detria/.
• A Python layer (src_python/tin_engine/): reading GeoTIFFs (tifffile), vector files and CRS (shapely, pyproj), configuration (Pydantic) and the CLI (Typer). The two meet through a pybind11 module, tin_engine._core.

project_structure.md describes the layout and the rules between the layers.

Where to read more

• INSTALL.md: installing, testing, and getting data.
• ROADMAP.md: what has been built and what comes next.
• docs/increments/: one design record per step of the work, with its measurements.

Publications

Bhattarai, B. C., Silantyeva, O., Teweldebrhan, A. T., Helset, S., Skavhaug, O., and Burkhart, J. F.: Impact of Catchment Discretization and Imputed Radiation on Model Response: A Case Study from Central Himalayan Catchment, Water, 12, 2020. https://doi.org/10.3390/w12092339

Silantyeva, O., Skavhaug, O., Bhattarai, B. C., Helset, S., Tallaksen, L. M., Nordaas, M., and Burkhart, J. F.: Shyft and Rasputin: a toolbox for hydrologic simulations on triangular irregular networks. https://doi.org/10.31223/X5CS95

Licence

MIT; see LICENSE. Third-party code and data credits are in NOTICE.md. Rasputin is developed by Expert Analytics.