Instancing, terrain & splines

Three geometry features handle large or procedural content. Instancing and terrain are first-class mesh fields (instancer and generator — see Meshes); both are deterministic (seeded, no Math.random), so a scene renders identically every load.

Instancing, terrain, and splines.

Instancing

Set a mesh’s instancer (+ instancerParams) to render many copies as a single InstancedMesh — one draw call. The built-in Grid instancer (packages/engine/src/scene/instancers/grid.ts) lays out a countX × countZ grid on the XZ plane (defaults 100×100 = 10,000 instances) with spacing and optional deterministic jitter (a seeded LCG). Register your own instancer to produce any per-instance matrix set.

Terrain

Set a mesh’s generator to "Terrain" (+ generatorParams) for a procedural heightfield (packages/engine/src/scene/geometries/terrain.ts): a horizontal XZ plane displaced in +Y by a deterministic sum of sines. Params: width, depth (world size), segments (grid resolution), amplitude (max height), frequency (wave scale). Pair it with a trimesh collider so physics matches the visual surface.

Splines

The spline schema (packages/engine/src/scene/schema/spline.ts) defines a CatmullRomCurve3 from points (≥ 2 control points), with closed (loop), curveType (catmullrom / centripetal / chordal), tension (default 0.5, used only for catmullrom), and resolution (line segments). Use splines for paths, camera rails, or procedural placement.

Determinism by design

Both the grid instancer and the terrain generator avoid Math.random (seeded LCG / pure sum-of-sines) so the same scene always looks the same — important for reproducible builds.

See also

• Rendering, cameras & meshes — the instancer / generator mesh fields.
• Particles — the other large-content feature.
• Scene Schema reference — mesh + spline fields.