Trees and scatter

This page builds on the vegetation, whose wind field already moves the grass, the great oak's crown and the clouds, and on the terrain's shapes, whose biome weights and paint strokes decide what grows where. Windrise has one hand-built oak and a field of grass. A region needs forests of its own species, the flowers and rocks between them, and plants that part as something walks through.

Decisions

• Species are parameters of one generator. The tree kit's generator already builds a trunk and branches carrying clusters of leaf cards whose normals are bent outward, so a crown lights like a soft sphere. The oak, the pine, the maple, the sakura and the rainforest giants are each a set of its parameters, and a region's page adds its species.
• Level of detail by impostor. Beyond the near range, a tree becomes a camera-facing impostor baked from its own mesh once, at startup. Far forests become the terrain's colour. Instancing gives one draw per species per detail level.
• Scatter is deterministic. Flowers, bushes, mushrooms, rocks and pickable plants are scattered in each terrain tile by a seeded, blue-noise-spaced placement filtered by biome, slope and paint, in the terrain's worker, so the same spot always grows the same plants. Hand-placed landmark plants, such as Windrise's great oak, come from the landmark schema instead.
• Plants yield to what passes through. Grass bends away from the character through a small trail texture around the viewer, written by the character controller.

How it works

flowchart TD
  TILE[Terrain tile: biome, slope, paint] --> SC[Seeded blue-noise scatter in the worker]
  SC --> SP{Species by biome}
  SP -->|near| MESH[Trunk and rounded leaf cards, instanced]
  SP -->|far| IMP[Baked impostor, instanced]
  WF[Wind field] --> MESH
  WF --> IMP
  CH[Character] --> TR[Trail texture]
  TR --> G[Grass bends away]

Scope

Today: the vegetation grows grass in two rings on green ground and sways Windrise's one oak on the wind.

This adds:

1. Species for each region, as parameters.
2. Impostors and instancing per species.
3. Scatter in the terrain's worker.
4. The trail, with the character controller.

Key files

New files:

packages/genshin-engine/src/vegetation/     ← species parameters, scatter, impostor baking

Sources

• InstancedMesh, three.js: one draw per species and level of detail.