=== versions ===
python 3.12.0 | numpy 2.5.4 | rasterio 1.5.2 | shapely 2.2.0 | manifold3d 3.5.5 | pyvista 0.49.2

=== Step 1: DEM and land cover on one 20 m grid ===
grid 400 x 350 cells of 20 m | read and reprojected in 1.4 s
DEM: 53.6 - 1072.6 m, NaNs 0
WorldCover classes: tree cover 10.5%, grassland 86.7%, built-up 0.3%, bare / sparse 0.4%, permanent water 2.1%, herbaceous wetland 0.0%, moss and lichen 0.0%

=== Step 2: classify into four colours and remove unprintable specks ===
cell on the print 0.376 mm -> minimum region 1.5 mm2 = 11 cells
water        regions   17 ->  11 | area   2.1% ->   2.1%
woodland     regions  273 ->  65 | area  10.5% ->  10.2%
open ground  regions   67 ->  16 | area  79.1% ->  79.5%
high ground  regions    6 ->   3 | area   8.3% ->   8.3%
cells changed by the sieve: 772 (0.55%)

=== Step 3: terrain solid ===
horizontal scale 1:53,200 | model 150.0 x 131.2 x 31.7 mm
lakes lowered by 0.4 mm at 2,920 vertices
single-extruder alternative: change filament at z = 21.22 mm for ground above 700 m

=== Step 4: one watertight part per colour ===
A: full-depth colours    accent colours 59.18 cm3 | 152 of 159 layers (0.2 mm) need more than one filament
B: 1.2 mm colour caps    accent colours  4.85 cm3 | 144 of 159 layers (0.2 mm) need more than one filament
water        dropped   0 slivers totalling 0.0000 mm3
woodland     dropped   0 slivers totalling 0.0000 mm3
open ground  dropped 178 slivers totalling 0.0000 mm3
high ground  dropped   0 slivers totalling 0.0000 mm3
water          20,536 triangles | watertight True | oriented True | volume   0.49 cm3
woodland      106,628 triangles | watertight True | oriented True | volume   2.39 cm3
open ground   626,896 triangles | watertight True | oriented True | volume 257.33 cm3
high ground    63,410 triangles | watertight True | oriented True | volume   1.96 cm3
sum of parts 262.176 cm3 | whole terrain 262.176 cm3 | pairwise overlap -0.0005 mm3
water         11 separate piece(s)
woodland      65 separate piece(s)
open ground    1 separate piece(s)
high ground    3 separate piece(s)

=== Step 5: write STLs and a 3MF ===
yr_wyddfa_1_water.stl                1.0 MB
yr_wyddfa_2_woodland.stl             5.3 MB
yr_wyddfa_3_open_ground.stl         31.3 MB
yr_wyddfa_4_high_ground.stl          3.2 MB
yr_wyddfa_multicolour.3mf            7.4 MB | parts: water, woodland, open ground, high ground

=== figures ===
wrote 01-dem-and-land-cover, 02-colour-regions-sieve, 03-stl-preview-multicolour, 04-stl-parts