# CatmullRomSpline

#### new Cesium.CatmullRomSpline(options)
engine/Source/Core/CatmullRomSpline.js 150

A Catmull-Rom spline is a cubic spline where the tangent at control points, except the first and last, are computed using the previous and next control points. Catmull-Rom splines are in the class C1.

Name | Type | Description
--- | --- | ---
`options` | object | Object with the following properties:
Name | Type | Description
--- | --- | ---
`times` | Array.<number> | An array of strictly increasing, unit-less, floating-point times at each point. The values are in no way connected to the clock time. They are the parameterization for the curve.
`points` | Array.<Cartesian3> | The array of `Cartesian3` control points.
`firstTangent` | Cartesian3 | optional The tangent of the curve at the first control point. If the tangent is not given, it will be estimated.
`lastTangent` | Cartesian3 | optional The tangent of the curve at the last control point. If the tangent is not given, it will be estimated.

##### Throws:

- DeveloperError : points.length must be greater than or equal to 2.
- DeveloperError : times.length must be equal to points.length.

##### Example:

    // spline above the earth from Philadelphia to Los Angeles
    const spline = new Cesium.CatmullRomSpline({
        times : [ 0.0, 1.5, 3.0, 4.5, 6.0 ],
        points : [
            new Cesium.Cartesian3(1235398.0, -4810983.0, 4146266.0),
            new Cesium.Cartesian3(1372574.0, -5345182.0, 4606657.0),
            new Cesium.Cartesian3(-757983.0, -5542796.0, 4514323.0),
            new Cesium.Cartesian3(-2821260.0, -5248423.0, 4021290.0),
            new Cesium.Cartesian3(-2539788.0, -4724797.0, 3620093.0)
        ]
    });

    const p0 = spline.evaluate(times[i]);         // equal to positions[i]
    const p1 = spline.evaluate(times[i] + delta); // interpolated value when delta < times[i + 1] - times[i]

##### See:

- ConstantSpline
- SteppedSpline
- HermiteSpline
- LinearSpline
- QuaternionSpline
- MorphWeightSpline

### Members

#### readonly firstTangent : Cartesian3
engine/Source/Core/CatmullRomSpline.js 235

The tangent at the first control point.

#### readonly lastTangent : Cartesian3
engine/Source/Core/CatmullRomSpline.js 249

The tangent at the last control point.

#### readonly points : Array.<Cartesian3>
engine/Source/Core/CatmullRomSpline.js 221

An array of `Cartesian3` control points.

#### readonly times : Array.<number>
engine/Source/Core/CatmullRomSpline.js 207

An array of times for the control points.

### Methods

#### clampTime(time) → number
engine/Source/Core/CatmullRomSpline.js 308

Clamps the given time to the period covered by the spline.

Name | Type | Description
--- | --- | ---
`time` | number | The time.

##### Returns:

The time, clamped to the animation period.

#### evaluate(time, result) → Cartesian3
engine/Source/Core/CatmullRomSpline.js 321

Evaluates the curve at a given time.

Name | Type | Description
--- | --- | ---
`time` | number | The time at which to evaluate the curve.
`result` | Cartesian3 | optional The object onto which to store the result.

##### Returns:

The modified result parameter or a new instance of the point on the curve at the given time.

##### Throws:

- DeveloperError : time must be in the range `[t0, tn]`, where `t0` is the first element in the array `times` and `tn` is the last element in the array `times`.

#### findTimeInterval(time) → number
engine/Source/Core/CatmullRomSpline.js 290

Finds an index `i` in `times` such that the parameter `time` is in the interval `[times[i], times[i + 1]]`.

Name | Type | Description
--- | --- | ---
`time` | number | The time.

##### Returns:

The index for the element at the start of the interval.

##### Throws:

- DeveloperError : time must be in the range `[t0, tn]`, where `t0` is the first element in the array `times` and `tn` is the last element in the array `times`.

#### wrapTime(time) → number
engine/Source/Core/CatmullRomSpline.js 299

Wraps the given time to the period covered by the spline.

Name | Type | Description
--- | --- | ---
`time` | number | The time.

##### Returns:

The time, wrapped around to the updated animation.

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