Build worlds
from a graph.

Two domains in one graph

The raster domain holds buffers — neighbour-aware, where erosion lives. The field domain evaluates a single point in 3D and is therefore resolution-independent. Rasterize and Sample bridge them, so a procedural field can be baked for erosion and an eroded heightfield read back by a field graph.

A field network is transpiled to GLSL and evaluated on the GPU, sharing its noise implementation with the planet renderer. CPU and GPU results are verified to agree within 1.3 × 10^-5 across 20,480 samples.

Erosion that models the physics

Six independent solvers, each reporting what it did as reusable masks:

• Particle-droplet hydraulic — inertia, carry capacity, evaporation; outputs erosion, deposition, standing water, exposed bedrock and signed change.
• Shallow-water pipe model — a virtual-pipe solver for flowing water.
• Stream-power fluvial incision — E = K·Am·Sn, explicit or implicit (Braun–Willett) with tectonic uplift and rock hardness.
• Thermal weathering — talus to an angle of repose given in real degrees (scree settles near 35°).
• Aeolian — windward abrasion, leeward deposition, dunes.
• Priority-Flood basin filling — floods closed basins to their outlet height, so D8 routing no longer dead-ends in pits.

Terrain analysis you can wire into a material

D8 flow accumulation measures how much water passes through each point. The wetness index — ln(a / tan b) — is the standard measure of where water collects: high in flat hollows fed from above, low on steep ground. Both are ordinary graph outputs, so a moss or vegetation mask sits where hydrology says it should.

ErosionLayers turns a simulation's side channels into a priority-ordered stack of masks — bedrock, scree, soil, grass, sediment, riverbed, snow — that always sum to one, and packs them into two splat textures.

Adaptive tessellation, crack-free

The terrain is subdivided to what the camera needs, not to a fixed grid: 64×64 patches, each edge subdivided by that edge's length in pixels, from an effective 512 across — exactly the fixed grid it replaces, so it is never coarser — up to 2048 where the camera is close.

Levels are chosen per edge from its two endpoints, so adjacent patches always agree and no crack can open. Spacing is fractional, so a patch's level changes continuously rather than popping.

Materials that read the displaced surface

A layer's distribution answers where the material belongs — by altitude, steepness and which way the ground faces, each with a soft band. The criteria multiply, so a material sits where every condition holds: "rock, on the steep bits, below the snow line."

Because distribution reads the surface after displacement, slope and facing come from the shaded normal — so the material follows detail finer than the heightmap carrying it. Each layer carries its own albedo, normal and roughness, and decides whether its relief adds to the layer beneath (lichen on rock) or replaces it (snow flattening what it covers).

Planets as functions, not meshes

A planet is a pure parameter block — radius, relief, seed, sea level, snow line, colours, atmosphere — generated on the GPU every frame. No textures, no meshes, no caches, so a hundred planets cost the same memory as one.

Radius is a real length from a tenth of a millimetre to a billion kilometres. Single-precision positions resolve a globe to about a millionth of the tile width — 1 cm at the default 5 km tile. Sub-pixel planets are skipped, sphere meshes swap through three LODs with hysteresis so they never flicker, and surface shading always evaluates two octaves finer than the geometry.