import { AssetError, type Result } from '@forgeax/engine-types';
/** Write a finite unit tangent in the normal plane; leave output unchanged on failure.
 * Writes xyz only, so the producer retains its own handedness policy.
 */
export declare function writeNormalPlaneTangent(out: Float32Array, offset: number, nx: number, ny: number, nz: number): boolean;
/**
 * Compute per-vertex tangent (vec4) for a procedural mesh using path A
 * (UV-derivative + face-area-weighted average + Gram-Schmidt + handedness).
 *
 * @param positions Float32Array, vertexCount * 3 (xyz interleaved).
 * @param normals Float32Array, vertexCount * 3 (xyz interleaved); must be
 *   pre-normalised by the caller (procedural factories already produce
 *   unit-length normals at vertex emit time).
 * @param uvs Float32Array, vertexCount * 2 (uv interleaved).
 * @param indices optional Uint16Array | Uint32Array triangle list; when
 *   undefined, sequential triangulation 0,1,2,3,4,5,... is assumed.
 * @returns `Result<Float32Array, AssetError>` with a Float32Array of
 *   vertexCount * 4 on success. `.xyz` is the tangent and `.w` is the
 *   handedness sign in {+1, -1}; malformed topology returns the existing
 *   `asset-parse-failed` AssetError before working or output buffers exist.
 *
 * @remarks
 * Path A formula (per triangle):
 * ```
 * dP1 = p2 - p1; dP2 = p3 - p1
 * dUV1 = uv2 - uv1; dUV2 = uv3 - uv1
 * det = dUV1.u * dUV2.v - dUV2.u * dUV1.v
 * T_face = (dUV2.v * dP1 - dUV1.v * dP2) / det
 * sign = det >= 0 ? +1 : -1
 * ```
 * Per-vertex aggregation: accumulate `T_face * faceArea` into the three
 * vertices of the triangle; accumulate `sign` (the dominant sign per
 * vertex wins). After accumulation: Gram-Schmidt against the supplied
 * normal `T' = normalize(T - dot(T, N) * N)`; repack as vec4 with the
 * dominant handedness sign.
 */
export declare function computeTangentVec4(positions: Float32Array, normals: Float32Array, uvs: Float32Array, indices?: Uint16Array | Uint32Array): Result<Float32Array, AssetError>;
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