Namespace lod

Model LOD Shell Generation

The model.lod module builds coarse triangle shells from existing SceneObjects and can install those shells as SceneModel representation sets. A shell is generated in model space from source triangle geometry, then referenced by a shell representation in the same SceneModel as the detailed source objects.

Shell generation is offline or setup-time work. It does not change scene visibility and does not install any camera-driven switching. Use createShellRep to author representation sets, and RepresentationLODSelector when you want runtime per-view LOD switching over those authored representations.

Public callers should normally use ShellGenerator, generateShellFromSceneObjects or createShellRep. Lower-level voxelization and extraction helpers are exported for SDK tests and tooling, but are not part of the stable authored-LOD API.

Pipeline

%%{init:{"theme":"dark"}}%% flowchart TD A["SceneObject[]"] --> B["collectShellSourceTriangles"] B --> C["voxelizeShellTriangles"] C --> D["floodShellExterior"] D --> E["extractShellMesh"] E --> F{"surfaceNets?"} F -- yes --> G["smoothShellMesh"] F -- no --> H["simplifyShellMesh"] G --> H H --> I["ShellGeneratorResult"]

%%{init:{"theme":"default"}}%% flowchart TD A["SceneObject[]"] --> B["collectShellSourceTriangles"] B --> C["voxelizeShellTriangles"] C --> D["floodShellExterior"] D --> E["extractShellMesh"] E --> F{"surfaceNets?"} F -- yes --> G["smoothShellMesh"] F -- no --> H["simplifyShellMesh"] G --> H H --> I["ShellGeneratorResult"]

flowchart TD
    A["SceneObject[]"] --> B["collectShellSourceTriangles"]
    B --> C["voxelizeShellTriangles"]
    C --> D["floodShellExterior"]
    D --> E["extractShellMesh"]
    E --> F{"surfaceNets?"}
    F -- yes --> G["smoothShellMesh"]
    F -- no --> H["simplifyShellMesh"]
    G --> H
    H --> I["ShellGeneratorResult"]

Usage

Generate a shell directly from loaded scene objects:

import {ShellGenerator} from "@xeokit/sdk/model/lod";

const generator = new ShellGenerator();
const result = generator.generate(objects, {
  shellResolution: 64,
  extraction: "surfaceNets",
  smoothing: {
    iterations: 4
  },
  simplification: {
    targetTriangleCount: 5000
  }
});

console.log(result.positions, result.indices, result.stats);

Reuse collected triangles when comparing multiple shell settings:

import {
  collectShellSourceTriangles,
  generateShellFromTriangles
} from "@xeokit/sdk/model/lod";

const source = collectShellSourceTriangles(objects);
const coarse = generateShellFromTriangles(source, {shellResolution: 32});
const smooth = generateShellFromTriangles(source, {
  shellResolution: 96,
  extraction: "surfaceNets"
});

Create a SceneModel representation set from source objects:

import {createShellRep} from "@xeokit/sdk/model/lod";

const result = createShellRep({
  model: sceneModel,
  id: "tower-core-lod",
  objectIds: ["wall-01", "slab-01", "column-01"],
  generation: {
    shellResolution: 64,
    extraction: "surfaceNets"
  },
  selection: {
    strategy: "projectedSize",
    hysteresisPixels: 16
  },
  detailedRange: {
    minPixels: 128
  },
  shellRange: {
    maxPixels: 96
  }
});