export type FlowVec3 = readonly [number, number, number];
export interface FlowTubeConfig {
    from: FlowVec3;
    to: FlowVec3;
    /** Tube radius; flow strength fades from the axis to zero here. */
    radius: number;
    /** Axial flow speed on the core at full spool. */
    strength: number;
    /** Radial falloff exponent — `1` linear, `2` (default) keeps a fat core with soft edges. */
    falloff?: number;
    /** Extra reach past each end where the axial envelope fades to zero; default `0` (hard caps). */
    capFalloff?: number;
}
/**
 * An axial corridor of directional flow with radial core falloff and a spool scalar — fan tunnels,
 * updraft shafts, river narrows, thruster wash. Pure math: sample `velocityAt(point, spool)` and add
 * it to whatever integrator moves the body (walk controller drift, `BuoyantBody`, a custom sim).
 */
export interface FlowTube {
    readonly axis: FlowVec3;
    readonly length: number;
    /** Flow velocity at a world point, scaled by `spool` in `[0, 1]` (default `1`); zero outside the tube. */
    velocityAt(point: FlowVec3, spool?: number): FlowVec3;
    /** The radial × axial envelope in `[0, 1]` at a world point — feed particle density, audio gain, rumble. */
    intensityAt(point: FlowVec3): number;
}
export declare function createFlowTube(config: FlowTubeConfig): FlowTube;
/** Sum several tubes' flow at one point — each entry carries its own spool. */
export declare function combineFlowVelocity(tubes: readonly (FlowTube | {
    tube: FlowTube;
    spool: number;
})[], point: FlowVec3): FlowVec3;