Added VelocityVectorProperty #3908
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,184 @@ | ||
| /*global define*/ | ||
| define([ | ||
| '../Core/Cartesian3', | ||
| '../Core/defaultValue', | ||
| '../Core/defined', | ||
| '../Core/defineProperties', | ||
| '../Core/DeveloperError', | ||
| '../Core/Event', | ||
| '../Core/JulianDate', | ||
| './Property' | ||
| ], function( | ||
| Cartesian3, | ||
| defaultValue, | ||
| defined, | ||
| defineProperties, | ||
| DeveloperError, | ||
| Event, | ||
| JulianDate, | ||
| Property) { | ||
| 'use strict'; | ||
|
|
||
| /** | ||
| * A {@link Property} which evaluates to a {@link Cartesian3} vector | ||
| * based on the velocity of the provided {@link PositionProperty}. | ||
| * | ||
| * @alias VelocityVectorProperty | ||
| * @constructor | ||
| * | ||
| * @param {Property} [position] The position property used to compute the velocity. | ||
| * | ||
| * @example | ||
| * //Create an entity with position and orientation. | ||
| * var position = new Cesium.SampledProperty(); | ||
| * position.addSamples(...); | ||
| * var entity = viewer.entities.add({ | ||
| * position : position, | ||
| * orientation : new Cesium.VelocityVectorProperty(position) | ||
| * })); | ||
| */ | ||
| function VelocityVectorProperty(position) { | ||
| this._position = undefined; | ||
| this._subscription = undefined; | ||
| this._definitionChanged = new Event(); | ||
|
|
||
| this.position = position; | ||
| } | ||
|
|
||
| defineProperties(VelocityVectorProperty.prototype, { | ||
| /** | ||
| * Gets a value indicating if this property is constant. | ||
| * @memberof VelocityVectorProperty.prototype | ||
| * | ||
| * @type {Boolean} | ||
| * @readonly | ||
| */ | ||
| isConstant : { | ||
| get : function() { | ||
| return Property.isConstant(this._position); | ||
| } | ||
| }, | ||
| /** | ||
| * Gets the event that is raised whenever the definition of this property changes. | ||
| * @memberof VelocityVectorProperty.prototype | ||
| * | ||
| * @type {Event} | ||
| * @readonly | ||
| */ | ||
| definitionChanged : { | ||
| get : function() { | ||
| return this._definitionChanged; | ||
| } | ||
| }, | ||
| /** | ||
| * Gets or sets the position property used to compute orientation. | ||
| * @memberof VelocityVectorProperty.prototype | ||
| * | ||
| * @type {Property} | ||
| */ | ||
| position : { | ||
| get : function() { | ||
| return this._position; | ||
| }, | ||
| set : function(value) { | ||
| var oldValue = this._position; | ||
| if (oldValue !== value) { | ||
| if (defined(oldValue)) { | ||
| this._subscription(); | ||
| } | ||
|
|
||
| this._position = value; | ||
|
|
||
| if (defined(value)) { | ||
| this._subscription = value._definitionChanged.addEventListener(function() { | ||
| this._definitionChanged.raiseEvent(this); | ||
| }, this); | ||
| } | ||
|
|
||
| this._definitionChanged.raiseEvent(this); | ||
| } | ||
| } | ||
| } | ||
| }); | ||
|
|
||
| var position1Scratch = new Cartesian3(); | ||
| var position2Scratch = new Cartesian3(); | ||
| var velocityScratch = new Cartesian3(); | ||
| var timeScratch = new JulianDate(); | ||
| var step = 1.0 / 60.0; | ||
|
|
||
| /** | ||
| * Gets the value of the property at the provided time. | ||
| * | ||
| * @param {JulianDate} [time] The time for which to retrieve the value. | ||
| * @param {Cartesian3} [result] The object to store the value into, if omitted, a new instance is created and returned. | ||
| * @returns {Cartesian3} The modified result parameter or a new instance if the result parameter was not supplied. | ||
| */ | ||
| VelocityVectorProperty.prototype.getValue = function(time, result) { | ||
| return this._getValue(time, result); | ||
| }; | ||
|
|
||
| /** | ||
| * @private | ||
| */ | ||
| VelocityVectorProperty.prototype._getValue = function(time, velocityResult, positionResult) { | ||
| //>>includeStart('debug', pragmas.debug); | ||
| if (!defined(time)) { | ||
| throw new DeveloperError('time is required'); | ||
| } | ||
| //>>includeEnd('debug'); | ||
|
|
||
| if (!defined(velocityResult)) { | ||
| velocityResult = new Cartesian3(); | ||
| } | ||
|
|
||
| var property = this._position; | ||
| if (Property.isConstant(property)) { | ||
| return undefined; | ||
|
There was a problem hiding this comment. Wouldn't this be the zero vector instead of undefined? There was a problem hiding this comment. Well, I guess if you wanted the vector to always be normalized this makes sense. Just wanted to double check. There was a problem hiding this comment. The other properties seem to return undefined when there isn't a value at that time. This code was pretty much copied from the There was a problem hiding this comment. Yes, |
||
| } | ||
|
|
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| var position1 = property.getValue(time, position1Scratch); | ||
| var position2 = property.getValue(JulianDate.addSeconds(time, step, timeScratch), position2Scratch); | ||
|
|
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| //If we don't have a position for now, return undefined. | ||
| if (!defined(position1)) { | ||
| return undefined; | ||
| } | ||
|
|
||
| //If we don't have a position for now + step, see if we have a position for now - step. | ||
| if (!defined(position2)) { | ||
| position2 = position1; | ||
| position1 = property.getValue(JulianDate.addSeconds(time, -step, timeScratch), position2Scratch); | ||
|
|
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| if (!defined(position1)) { | ||
| return undefined; | ||
| } | ||
| } | ||
|
|
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| if (Cartesian3.equals(position1, position2)) { | ||
| return undefined; | ||
| } | ||
|
|
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| if (defined(positionResult)) { | ||
| position1.clone(positionResult); | ||
| } | ||
|
|
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| var velocity = Cartesian3.subtract(position2, position1, velocityScratch); | ||
| return Cartesian3.normalize(velocity, velocityResult); | ||
| }; | ||
|
|
||
| /** | ||
| * Compares this property to the provided property and returns | ||
| * <code>true</code> if they are equal, <code>false</code> otherwise. | ||
| * | ||
| * @param {Property} [other] The other property. | ||
| * @returns {Boolean} <code>true</code> if left and right are equal, <code>false</code> otherwise. | ||
| */ | ||
| VelocityVectorProperty.prototype.equals = function(other) { | ||
| return this === other ||// | ||
| (other instanceof VelocityVectorProperty && | ||
| Property.equals(this._position, other._position)); | ||
| }; | ||
|
|
||
| return VelocityVectorProperty; | ||
| }); | ||
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This example is now incorrect. I would recommend updating it to illustrate orienting a billboard along it's velocity vector.
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The comment is still incorrect. Change it to something like
//Create an entity with a billboard rotated to match its velocity