SteppedSpline

const times = [ 0.0, 1.5, 3.0, 4.5, 6.0 ];
const spline = new SteppedSpline({
    times : times,
    points : [
        new Cartesian3(1235398.0, -4810983.0, 4146266.0),
        new Cartesian3(1372574.0, -5345182.0, 4606657.0),
        new Cartesian3(-757983.0, -5542796.0, 4514323.0),
        new Cartesian3(-2821260.0, -5248423.0, 4021290.0),
        new Cartesian3(-2539788.0, -4724797.0, 3620093.0)
    ]
});

const p0 = spline.evaluate(times[0]);