/**
 * MeshletLODBuilder — Nanite-style hierarchical meshlet LOD generation
 *
 * Builds a DAG of meshlet LOD levels:
 *   LOD0: meshlets from the original high-poly mesh
 *   LOD1+: group meshlets, merge triangles, simplify, re-meshletize
 *
 * Each meshlet tracks its parent meshlets so the runtime can stream
 * and cull at the appropriate granularity for any screen size.
 *
 * @see HS-5 — Meshlet cluster generator directive
 */
import type { MeshData } from './LODGenerator';
import { Meshlet, type MeshletGeneratorOptions } from './MeshletGenerator';
/** A meshlet at a specific LOD level with parent-child links */
export interface HierarchicalMeshlet extends Meshlet {
    /** LOD level (0 = highest detail) */
    lodLevel: number;
    /** IDs of child meshlets that were merged to create this one */
    children: number[];
    /** IDs of parent meshlets this meshlet contributes to */
    parents: number[];
    /** Global meshlet ID across all LOD levels */
    globalId: number;
}
/** One level in the meshlet LOD hierarchy */
export interface MeshletLODLevel {
    /** LOD level index */
    level: number;
    /** Meshlets at this level */
    meshlets: HierarchicalMeshlet[];
    /** Total triangles at this level */
    totalTriangles: number;
    /** Total unique vertices at this level */
    totalVertices: number;
}
/** Complete hierarchical meshlet result */
export interface MeshletHierarchyResult {
    /** LOD levels from finest to coarsest */
    levels: MeshletLODLevel[];
    /** Total meshlets across all levels */
    totalMeshlets: number;
    /** Source triangle count */
    sourceTriangles: number;
    /** Generation time in ms */
    generationTimeMs: number;
    /** Reduction ratios per level */
    reductionRatios: number[];
}
/** Options for hierarchical meshlet generation */
export interface MeshletHierarchyOptions {
    /** Meshlet generation options */
    meshletOptions?: Partial<MeshletGeneratorOptions>;
    /** Target number of meshlets to group for simplification (default: 4) */
    groupSize: number;
    /** Number of LOD levels to generate (default: 3) */
    levelCount: number;
    /** Triangle reduction ratio per level (default: 0.5) */
    reductionRatio: number;
    /** Simplification algorithm */
    simplificationAlgorithm: 'quadricError' | 'edgeCollapse' | 'vertexClustering';
}
export declare const DEFAULT_HIERARCHY_OPTIONS: MeshletHierarchyOptions;
export declare class MeshletLODBuilder {
    private options;
    constructor(options?: Partial<MeshletHierarchyOptions>);
    /**
     * Build a hierarchical meshlet LOD structure from a mesh.
     *
     * Algorithm:
     * 1. Generate LOD0 meshlets from the original mesh
     * 2. For each subsequent level:
     *    a. Group meshlets from the previous level
     *    b. Merge their triangles into a sub-mesh
     *    c. Simplify the sub-mesh
     *    d. Re-meshletize the simplified mesh
     *    e. Link parent-child relationships
     */
    build(mesh: MeshData): MeshletHierarchyResult;
    /** Get current options */
    getOptions(): MeshletHierarchyOptions;
}
export declare function createMeshletLODBuilder(options?: Partial<MeshletHierarchyOptions>): MeshletLODBuilder;
/** Convenience: build hierarchy in one call */
export declare function buildMeshletHierarchy(mesh: MeshData, options?: Partial<MeshletHierarchyOptions>): MeshletHierarchyResult;
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