/**
 * LOD1 index simplification (issue #1682, phase 5).
 *
 * Vertex-clustering decimation in the style of meshoptimizer's "sloppy"
 * simplifier, over the batch's EXISTING interleaved vertex buffer: vertices
 * are snapped to a uniform grid, each occupied cell elects its first vertex
 * as representative, and a triangle survives only when its three corners
 * land in three DISTINCT cells. The output is just another index buffer over
 * the same vertices — LOD costs index bytes only, no second vertex buffer,
 * and the per-vertex entityId lane (picking id + colour salt) rides along
 * with the representative vertex.
 *
 * Works on ifc-lite's unwelded flat-shaded soup because clustering keys on
 * POSITION, not index topology: coincident duplicated vertices land in the
 * same cell and collapse together. Representative normals are "whichever
 * face got there first" — visually fine at the sub-`thresholdPx` projected
 * sizes LOD1 is drawn at, and the no-weld invariant (#846) is untouched
 * because the full-detail LOD0 geometry is never modified.
 */
/** Below this many source triangles a batch keeps LOD0 only. */
export declare const LOD_MIN_TRIANGLES = 500;
/** Grid cell edge as a fraction of the batch AABB diagonal (error budget). */
export declare const LOD_CELL_FRACTION = 0.02;
/**
 * Cluster-simplify `indices` over interleaved vertex data.
 *
 * @param vertexData interleaved records, `strideFloats` floats per vertex,
 *   position at float offset 0..2 (the batch layout: 7 floats = 28 bytes)
 * @param cellSize world-space grid edge; non-positive returns null
 * @returns the LOD1 index buffer, or null when simplification does not pay
 *   (too few source triangles, or the result is not meaningfully smaller)
 */
export declare function simplifyIndicesByClustering(vertexData: Float32Array, strideFloats: number, indices: Uint32Array, cellSize: number): Uint32Array | null;
/** Cell size for a batch from its world AABB (diagonal * LOD_CELL_FRACTION). */
export declare function lodCellSizeForBounds(min: readonly [number, number, number], max: readonly [number, number, number]): number;
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