export type FluidDimension = number | string;
export interface FluidKernelCoefficients {
    h: number;
    h2: number;
    h6: number;
    poly6Kernel: number;
    spiky: number;
    viscosity: number;
    dimension: 2 | 3;
}
export type FluidKernelCoefficients3D = Omit<FluidKernelCoefficients, 'dimension'>;
export type FluidDisplacement = readonly number[];
/**
 * Return Poly6, Spiky-gradient, and viscosity-laplacian coefficients.
 *
 * @param {number} smoothingRadius Compact support radius.
 * @param {number|string} [dimension=3] Spatial dimension.
 * @returns {{h:number,h2:number,h6:number,poly6Kernel:number,spiky:number,viscosity:number,dimension:number}}
 */
export declare function fluidKernelCoefficients(smoothingRadius: number, dimension?: FluidDimension): FluidKernelCoefficients;
/** Evaluate the active Poly6 density kernel. */
export declare function poly6KernelValue(distance: number, smoothingRadius: number, dimension?: FluidDimension): number;
/** Evaluate grad_i W( x_i - x_j ) for the active Spiky kernel. */
export declare function spikyGradient(displacement: FluidDisplacement, smoothingRadius: number, dimension?: FluidDimension): [number, number, number];
/** Evaluate the scalar Spiky kernel whose derivative is `spikyGradient`. */
export declare function spikyKernelValue(distance: number, smoothingRadius: number, dimension?: FluidDimension): number;
/** Evaluate the active viscosity-kernel Laplacian. */
export declare function viscosityLaplacianValue(distance: number, smoothingRadius: number, dimension?: FluidDimension): number;
/** Backward-compatible 3D kernel-coefficient helper. */
export declare function kernels3D(smoothingRadius: number): FluidKernelCoefficients3D;
/** Backward-compatible 2D kernel-coefficient helper. */
export declare function kernels2D(smoothingRadius: number): FluidKernelCoefficients3D;