The execution model is in blender-core. Custom GN tools are in blender-geometry-nodes, materials in blender-texturing (trims, vertex blends), and mood/weather in blender-time-of-day/blender-weather-fx.
One call each
scripts/terrain.py -- --size 400 --res 513 --height 60 --type ridged --erosion 30 --flatten 0 0 40 --material
scripts/terrain.py -- --heightmap //hm.png --size 1000 --res 1009 --height 120 --export-splat //T_Splat.png
scripts/scatter.py -- --target Terrain --collection Trees --density 0.02 --min-distance 5 --max-slope 25 --height-max 45
scripts/scatter.py -- --target Terrain --collection Rocks --density 0.05 --max-slope 70 --align 0.8 --name ENV_Rocks
scripts/kit_check.py -- --objects SM_Wall_4m SM_Floor_4m SM_Door_4m --grid 0.5 --fix
Terrain (terrain.py)
- Grid of
--res² verts over--sizem. Use 2^n + 1 for Unity (513/1025/2049,.raw16-bit LE) and UE Landscape's recommended sizes (505/1009/2017/4033, 16-bit PNG). Above 1025, tile it. --type fbm(rolling),ridged(mountains),hills(hetero terrain).--scale= feature size m.--erosion N= thermal erosion steps (talus 33°): slopes relax and debris fills valleys.--terracem = stepped flats.--flatten X Y R= a level play/build area blended back with a smoothstep.- Writes
ENV_Slope(deg/90) andENV_Height(0–1) point attributes.--materialbuilds grass/rock/snow from them: rock above 35°, snow above 75% height on slopes below ~40°, with noise-broken edges. - Engines:
--export-heightmap(PNG = 16-bit gray,.raw= 16-bit little-endian, row 0 = −Y edge; flip vertically in Unity if mirrored) plusheightmap_z_scale_mfor the import Z scale.--export-splat= 16-bit RGBA weights (R grass, G rock, B snow, sum 1) for terrain layers. Both are written Raw (no display transform): measured round-trip error < 0.001.
Scatter (scatter.py)
- One GN modifier per layer: Poisson disk (
--densityper m² max,--min-distancem), kept where the interpolated surface normal is within--max-slopeand Z is inside--height-min/max(object space).--mask= vertex group or float attribute as density factor (paint it, or useENV_Height). - Collection children are instanced at their own origins with random yaw,
--scalerange, and--align(0 = upright trees, 0.6–1 = rocks hugging the slope). The source collection is excluded from the view layer. - The result checks every instance against the real surface (
slope_max_deg,height_range) and counts per source. Instances stay instances.--realizeonly when an exporter or boolean needs real mesh. - Densities: forest trees 0.01–0.05/m² (min distance 4–8 m), bushes 0.05–0.2, rocks 0.01–0.1, grass clumps 2–20/m² (near camera only). Layer big → small: trees, then bushes masked away from trunks, then grass.
- Engines: glTF
export_gpu_instances=True(EXT_mesh_gpu_instancing), or--export-points file.json(world transforms, Z-up m, wxyz quats) for UE foliage/PCG or Unity instancing scripts. FBX needs realized geometry or one object per instance.
Modular kits (kit_check.py)
- Metrics first: pick a grid (0.5 m snap, 1/2/4 m modules) and keep it everywhere. Walls 3–4 m tall interior (player ~1.8 m eye 1.6 m, doors ≥ 1 × 2.2 m), floors 4 × 4 m, stairs 0.18 m rise / 0.28 m run. UE works in cm (×100 on import), Unity in m.
- Pivot convention (
--pivot cornerdefault,bottom-center,center) so pieces snap by increments. Footprint lengths are multiples of the grid. Thinner-than-a-cell dims (wall thickness, trims) may be off-grid. - Open edges only on the piece's outer faces (seams); holes inside are errors. Seam verts must be on the grid so neighbours weld visually. Texel density within 25% of the kit median (
--texturepx).SM_names (--prefix). --fixapplies rotation/scale and moves each origin to the pivot without moving geometry. Linked duplicates share mesh data, so fix the source once.- Break repetition with trims and decals (
blender-texturing), vertex-color blends, and rotated/mirrored variants (mirrors flip normals, so check withblender-asset-qa). Hide seams with trim pieces over joints.
Gotchas
- Apply terrain/kit scale before scattering. Densities and slopes are world-based.
- Scatter height is in the target's object space. Keep terrains at the origin or offset
--height-*. - Huge Poisson counts are slow. Scatter per tile/area, or lower the density in the viewport and raise it for renders.
- Validate terrain + scatter with
blender-asset-qa(floating instances on cliffs, z-fighting decals) andblender-game-optimization(instances, LODs, draw calls).