pyarchinit_dem_visualizer.py¶

Overview¶

This file contains 14 documented elements.

Functions¶

ensure_output_dir(sito)¶

Return the absolute directory where per-site dashboard artifacts are saved.

${PYARCHINIT_HOME}/site_dashboard/<sanitized-sito> — created as needed. Falls back to ~/pyarchinit/site_dashboard/<sito> when PYARCHINIT_HOME is not set.

Parameters: - sito

timestamped_name(prefix, ext)¶

Return <prefix>_YYYYMMDD_HHMMSS.<ext>.

Parameters: - prefix - ext

compute_dem_difference(layer_pre, layer_post, out_path)¶

Run QgsRasterCalculator pre@1 - post@1 using the pre-DEM's extent and pixel grid. Returns 0 on success (QGIS convention).

Parameters: - layer_pre - layer_post - out_path

compute_volume_stats(diff_layer, cut_threshold)¶

Iterate the raster block once and return a dictionary of stats:

{'total_area_m2', 'total_volume_m3', 'cut_volume_m3', 'fill_volume_m3', 'max_abs', 'min_value', 'max_value'}

cut_volume = volume removed (diff > threshold, pre higher than post)
fill_volume = volume added (diff < -threshold)
total_area = area where |diff| > threshold
total_volume = sum(|diff|) * pixel_area (gross earth movement)

Parameters: - diff_layer - cut_threshold

style_diff_raster(layer, max_abs)¶

Apply a diverging color ramp centered on zero to a DEM difference raster.

Positive values (cut / removed material) are rendered in red, negative values (fill / added material) in blue.

Parameters: - layer - max_abs

style_cut_polygon(layer)¶

Semi-transparent red hatched fill for the intervention polygon.

Parameters: - layer

polygonize_cut_area(diff_raster_path, out_vector_path, threshold)¶

Vectorize the area where |diff| > threshold into a polygon layer.

Uses gdal:rastercalculator + gdal:polygonize via QGIS processing. Returns the path on success, None on failure.

Parameters: - diff_raster_path - out_vector_path - threshold

add_layer_to_group(layer, group_name, expanded)¶

Insert layer into QgsProject under a dedicated layer-tree group.

Parameters: - layer - group_name - expanded

zoom_canvas_to(iface, rect)¶

Zoom the main map canvas to the given QgsRectangle + refresh.

Parameters: - iface - rect

clip_raster_by_polygon(raster_path, poly_layer, out_path, dst_nodata, target_x_res, target_y_res, target_bounds)¶

Clip a raster to a polygon layer using gdal.Warp with a temporary cutline shapefile.

Returns (out_path, None) on success, (None, error_message) on failure. Safe in all QGIS profiles: does not rely on the processing framework.

Handles: - layer source URIs with |layername=... suffixes (GPKG, ...) - polygon layers in a different CRS than the raster (passes cutlineSRS) - memory vector layers (exported via QgsVectorFileWriter to a temp shapefile)

The optional target_x_res / target_y_res / target_bounds parameters force the output raster onto a specific pixel grid — pass the same values to both the pre and post DEM clips so the two outputs are perfectly aligned and can be subtracted by QgsRasterCalculator without resampling artefacts.

Parameters: - raster_path - poly_layer - out_path - dst_nodata - target_x_res - target_y_res - target_bounds

exclude_polygons_from_raster(raster_path, poly_layer, nodata_value)¶

Burn the features of poly_layer into raster_path using nodata_value, effectively removing those areas from any downstream volume calculation. Modifies the raster in place.

Used by the Computo Metrico workflow to subtract walls / built structures from the excavation volume: the wall polygons are rasterised onto the (already-clipped) DEM-difference raster, and the burned cells become NODATA so compute_volume_stats skips them.

Returns (True, None) on success, (False, error) otherwise.

Parameters: - raster_path - poly_layer - nodata_value

create_tin_mesh_from_dem(dem_layer, out_mesh_path, max_cells, clip_poly_layer)¶

Convert a DEM raster into a regular-grid 2DM mesh using a pure Python writer.

Earlier versions of this function invoked native:pixelstopoints + native:tinmeshcreation via the QGIS Processing framework, which crashed QGIS on some builds. The new implementation:

Reads the DEM directly with GDAL (no Processing).
Downsamples in-memory with NumPy if the grid exceeds max_cells.
Writes a 2DM mesh file manually: one quad (E4Q) per valid DEM cell, nodes at pixel centres.

Because no processing algorithm is invoked, this is safe across all QGIS versions and never triggers a segfault.

If clip_poly_layer is set, only cells whose centre lies inside the polygon (via a pre-clipped GDAL warp) are kept — the mesh then represents the excavation area only.

Parameters: - dem_layer - out_mesh_path - max_cells - clip_poly_layer

load_mesh_layer(mesh_path, name)¶

Load a 2DM mesh file as a QgsMeshLayer.

Historical note: previous versions also applied an automatic scalar renderer via _style_mesh_terrain. That path was dropped because calling QgsMeshRendererScalarSettings APIs from Python triggers a segfault on several QGIS builds (the signatures are unstable across minor versions). The caller is responsible for styling the mesh, or — preferably — for visualising the DEM directly via the matplotlib 3D fallback without ever creating a mesh layer.

Parameters: - mesh_path - name