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import Frozen from "./Frozen.js";
import defined from "./defined.js";
import DeveloperError from "./DeveloperError.js";
import Spline from "./Spline.js";
/**
* A spline that uses piecewise linear interpolation to create a curve.
*
* @alias LinearSpline
* @constructor
*
* @param {object} options Object with the following properties:
* @param {number[]} options.times 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.
* @param {number[]|Cartesian3[]} options.points The array of control points.
*
* @exception {DeveloperError} points.length must be greater than or equal to 2.
* @exception {DeveloperError} times.length must be equal to points.length.
*
*
* @example
* const times = [ 0.0, 1.5, 3.0, 4.5, 6.0 ];
* const spline = new Cesium.LinearSpline({
* times : times,
* 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[0]);
*
* @see ConstantSpline
* @see SteppedSpline
* @see HermiteSpline
* @see CatmullRomSpline
* @see QuaternionSpline
* @see MorphWeightSpline
*/
function LinearSpline(options) {
options = options ?? Frozen.EMPTY_OBJECT;
const points = options.points;
const times = options.times;
//>>includeStart('debug', pragmas.debug);
if (!defined(points) || !defined(times)) {
throw new DeveloperError("points and times are required.");
}
Iif (points.length < 2) {
throw new DeveloperError(
"points.length must be greater than or equal to 2.",
);
}
if (times.length !== points.length) {
throw new DeveloperError("times.length must be equal to points.length.");
}
//>>includeEnd('debug');
this._times = times;
this._points = points;
this._pointType = Spline.getPointType(points[0]);
this._lastTimeIndex = 0;
}
Object.defineProperties(LinearSpline.prototype, {
/**
* An array of times for the control points.
*
* @memberof LinearSpline.prototype
*
* @type {number[]}
* @readonly
*/
times: {
get: function () {
return this._times;
},
},
/**
* An array of {@link Cartesian3} control points.
*
* @memberof LinearSpline.prototype
*
* @type {number[]|Cartesian3[]}
* @readonly
*/
points: {
get: function () {
return this._points;
},
},
});
/**
* Finds an index <code>i</code> in <code>times</code> such that the parameter
* <code>time</code> is in the interval <code>[times[i], times[i + 1]]</code>.
* @function
*
* @param {number} time The time.
* @returns {number} The index for the element at the start of the interval.
*
* @exception {DeveloperError} time must be in the range <code>[t<sub>0</sub>, t<sub>n</sub>]</code>, where <code>t<sub>0</sub></code>
* is the first element in the array <code>times</code> and <code>t<sub>n</sub></code> is the last element
* in the array <code>times</code>.
*/
LinearSpline.prototype.findTimeInterval = Spline.prototype.findTimeInterval;
/**
* Wraps the given time to the period covered by the spline.
* @function
*
* @param {number} time The time.
* @return {number} The time, wrapped around to the updated animation.
*/
LinearSpline.prototype.wrapTime = Spline.prototype.wrapTime;
/**
* Clamps the given time to the period covered by the spline.
* @function
*
* @param {number} time The time.
* @return {number} The time, clamped to the animation period.
*/
LinearSpline.prototype.clampTime = Spline.prototype.clampTime;
/**
* Evaluates the curve at a given time.
*
* @param {number} time The time at which to evaluate the curve.
* @param {Cartesian3} [result] The object onto which to store the result.
* @returns {number|Cartesian3} The modified result parameter or a new instance of the point on the curve at the given time.
*
* @exception {DeveloperError} time must be in the range <code>[t<sub>0</sub>, t<sub>n</sub>]</code>, where <code>t<sub>0</sub></code>
* is the first element in the array <code>times</code> and <code>t<sub>n</sub></code> is the last element
* in the array <code>times</code>.
*/
LinearSpline.prototype.evaluate = function (time, result) {
const points = this.points;
const times = this.times;
const i = (this._lastTimeIndex = this.findTimeInterval(
time,
this._lastTimeIndex,
));
const u = (time - times[i]) / (times[i + 1] - times[i]);
const PointType = this._pointType;
if (PointType === Number) {
return (1.0 - u) * points[i] + u * points[i + 1];
}
if (!defined(result)) {
result = new Cartesian3();
}
return Cartesian3.lerp(points[i], points[i + 1], u, result);
};
export default LinearSpline;
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