export default class Interpolation {
    private static _interpolate;
    static linear<T extends number | number[]>(t: number, { preValue, nextValue }: {
        preValue: T;
        nextValue: T;
    }): T;
    static step(t: number, { preValue, nextValue }: {
        preValue: number[];
        nextValue: number[];
    }): number[];
    private static _quaternionSlerp;
    /**
       * https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#appendix-c-spline-interpolation
       tangents (ak, bk) and values (vk) are grouped within keyframes:
       a1,a2,...an,v1,v2,...vn,b1,b2,...bn
    
       Given a set of keyframes
    
       Input tk with Output in-tangent ak, point vk, and out-tangent bk for k = 1,...,n
    
       a spline segment between two keyframes is represented in a cubic Hermite spline form:
        p(t) = (2t3 - 3t2 + 1)p0 + (t3 - 2t2 + t)m0 + (-2t3 + 3t2)p1 + (t3 - t2)m1
    
        where
        
        t is a value between 0 and 1
        p0 is the starting point at t = 0
        m0 is the scaled starting tangent at t = 0
        p1 is the ending point at t = 1
        m1 is the scaled ending tangent at t = 1
        p(t) is the resulting point value
        
        and where at input offset tcurrent with keyframe index k
    
        t = (tcurrent - tk) / (tk+1 - tk)
        p0 = vk
        m0 = (tk+1 - tk)bk
        p1 = vk+1
        m1 = (tk+1 - tk)ak+1
       *
       * @param frameIndex
       * @param nextFrameIndex
       */
    /**
     * 三次样条插值
     * @param preValue
     * @param nextValue
     * @param t
     */
    private static _cubicSpline;
    static cubicSpline(t: number, { preFrameIndex, nextFrameIndex, keyLength, keyFrames }: {
        preFrameIndex: any;
        nextFrameIndex: any;
        keyLength: any;
        keyFrames: any;
    }): any[];
}