import type { TSLNode, TSLNodeFactory, TSLVec4Node } from '../types/tsl.js';
export interface StructureTensorNodeFactory extends TSLNodeFactory<[
    textureNode: TSLNode
], TSLVec4Node> {
    setParameterLength(length: number): this;
}
/**
 * Compute structure tensor for edge-aware image filtering.
 *
 * **Algorithm**
 * - Computes image gradients using Sobel operator (3×3 kernel)
 * - Calculates outer product of gradient: `J = [∇I ⊗ ∇I]`
 * - Outputs (Jxx, Jyy, Jxy) in RGB channels for downstream use
 *
 * **Use Cases**
 * - Input for Kuwahara filter (`kuwahara`)
 * - Edge detection and orientation analysis
 * - Anisotropic filtering and diffusion
 *
 * **Pipeline**
 * Structure tensor is typically used as a first pass before applying
 * edge-aware filters like Kuwahara.
 *
 * ```js
 * import { structureTensor } from 'three-blocks/experimental/core-tsl-effects';
 * import { kuwahara } from 'three-blocks';
 * import { pass } from 'three/tsl';
 *
 * // First pass: compute structure tensor
 * const scenePass = pass(scene, camera);
 * const tensorPass = structureTensor(scenePass);
 *
 * // Second pass: use tensor for edge-aware filtering
 * const filtered = kuwahara(scenePass, tensorPass, { radius: 5 });
 *
 * renderPipeline.outputNode = filtered;
 * ```
 *
 * @function structureTensor
 * @category TSL
 * @tags WebGPU, WebGL
 * @tsl
 * @param {Node} textureNode Source texture for gradient analysis.
 * @returns {Node.<vec4>} Structure tensor (Jxx, Jyy, Jxy, 1.0) in RGBA.
 * @see kuwahara
 */
export declare const structureTensor: StructureTensorNodeFactory;