Ability to change atmosphere color

    Issue: CesiumGS#3439

    Change the atmoshphere color

Author: kepta

Source/Scene/SkyAtmosphere.js

@@ -1,6 +1,7 @@
 /*global define*/
 define([
         '../Core/Cartesian3',
+        '../Core/Color',
         '../Core/defaultValue',
         '../Core/defined',
         '../Core/defineProperties',
@@ -22,6 +23,7 @@ define([
         './SceneMode'
     ], function(
         Cartesian3,
+        Color,
         defaultValue,
         defined,
         defineProperties,
@@ -54,15 +56,17 @@ define([
      * @alias SkyAtmosphere
      * @constructor
      *
-     * @param {Ellipsoid} [ellipsoid=Ellipsoid.WGS84] The ellipsoid that the atmosphere is drawn around.
+     * @param {Object} [options] Object with the following properties:
+     * @param {Ellipsoid} [options.ellipsoid=Ellipsoid.WGS84] The ellipsoid that the atmosphere is drawn around.
+     * @param {Color} [options.color=Color(1.0, 1.0, 1.0, 1.0)] The color of atmosphere.
      *
      * @example
      * scene.skyAtmosphere = new Cesium.SkyAtmosphere();
      *
      * @see Scene.skyAtmosphere
      */
-    function SkyAtmosphere(ellipsoid) {
-        ellipsoid = defaultValue(ellipsoid, Ellipsoid.WGS84);
+    function SkyAtmosphere(options) {
+        options = defaultValue(options, defaultValue.EMPTY_OBJECT);
 
         /**
          * Determines if the atmosphere is shown.
@@ -71,18 +75,17 @@ define([
          * @default true
          */
         this.show = true;
-
-        this._ellipsoid = ellipsoid;
+        this._ellipsoid = defaultValue(options.ellipsoid, Ellipsoid.WGS84);
+        this._color = defaultValue(options.color, new Color());
         this._command = new DrawCommand({
             owner : this
         });
         this._spSkyFromSpace = undefined;
         this._spSkyFromAtmosphere = undefined;
-
         this._fCameraHeight = undefined;
         this._fCameraHeight2 = undefined;
-        this._outerRadius = Cartesian3.maximumComponent(Cartesian3.multiplyByScalar(ellipsoid.radii, 1.025, new Cartesian3()));
-        var innerRadius = ellipsoid.maximumRadius;
+        this._outerRadius = Cartesian3.maximumComponent(Cartesian3.multiplyByScalar(this._ellipsoid.radii, 1.025, new Cartesian3()));
+        var innerRadius = this._ellipsoid.maximumRadius;
         var rayleighScaleDepth = 0.25;
 
         var that = this;
@@ -111,6 +114,15 @@ define([
             },
             fScaleOverScaleDepth : function() {
                 return (1.0 / (that._outerRadius - innerRadius)) / rayleighScaleDepth;
+            },
+            fRedColor : function() {
+                return that._color.red;
+            },
+            fGreenColor : function() {
+                return that._color.green;
+            },
+            fBlueColor : function() {
+                return that._color.blue;
             }
         };
     }
@@ -127,7 +139,19 @@ define([
             get : function() {
                 return this._ellipsoid;
             }
-        }
+        },
+        /**
+         * Gets the color of the atmosphere.
+         * @memberof SkyAtmosphere.prototype
+         *
+         * @type {Color}
+         * @readonly
+         */
+         color : {
+             get : function() {
+                 return this._color;
+             }
+         }
     });
 
     /**
@@ -239,7 +263,7 @@ define([
      *
      * @example
      * skyAtmosphere = skyAtmosphere && skyAtmosphere.destroy();
-     * 
+     *
      * @see SkyAtmosphere#isDestroyed
      */
     SkyAtmosphere.prototype.destroy = function() {

Source/Shaders/SkyAtmosphereVS.glsl

@@ -2,11 +2,11 @@
  * @license
  * Copyright (c) 2000-2005, Sean O'Neil (s_p_oneil@hotmail.com)
  * All rights reserved.
- * 
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
- * 
+ *
  * * Redistributions of source code must retain the above copyright notice,
  *   this list of conditions and the following disclaimer.
  * * Redistributions in binary form must reproduce the above copyright notice,
@@ -15,7 +15,7 @@
  * * Neither the name of the project nor the names of its contributors may be
  *   used to endorse or promote products derived from this software without
  *   specific prior written permission.
- * 
+ *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
@@ -29,10 +29,10 @@
  *
  * Modifications made by Analytical Graphics, Inc.
  */
- 
+
  // Code:  http://sponeil.net/
  // GPU Gems 2 Article:  http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter16.html
-  
+
 attribute vec4 position;
 
 uniform float fCameraHeight;
@@ -43,6 +43,9 @@ uniform float fInnerRadius;     // The inner (planetary) radius
 uniform float fScale;           // 1 / (fOuterRadius - fInnerRadius)
 uniform float fScaleDepth;      // The scale depth (i.e. the altitude at which the atmosphere's average density is found)
 uniform float fScaleOverScaleDepth; // fScale / fScaleDepth
+uniform float fRedColor; // The atmosphere color's red component
+uniform float fGreenColor; // The atmosphere color's green component
+uniform float fBlueColor; // The atmosphere color's blue component
 
 const float Kr = 0.0025;
 const float fKr4PI = Kr * 4.0 * czm_pi;
@@ -51,12 +54,9 @@ const float fKm4PI = Km * 4.0 * czm_pi;
 const float ESun = 15.0;
 const float fKmESun = Km * ESun;
 const float fKrESun = Kr * ESun;
-const vec3 v3InvWavelength = vec3(
-    5.60204474633241,  // Red = 1.0 / Math.pow(0.650, 4.0)
-    9.473284437923038, // Green = 1.0 / Math.pow(0.570, 4.0)
-    19.643802610477206); // Blue = 1.0 / Math.pow(0.475, 4.0)
+
 const float rayleighScaleDepth = 0.25;
-          
+
 const int nSamples = 2;
 const float fSamples = 2.0;
 
@@ -105,6 +105,7 @@ void main(void)
     float fScaledLength = fSampleLength * fScale;
     vec3 v3SampleRay = v3Ray * fSampleLength;
     vec3 v3SamplePoint = v3Start + v3SampleRay * 0.5;
+    vec3 v3InvWavelength = vec3(fRedColor / pow(0.650, 4.0), fGreenColor / pow(0.570, 4.0), fBlueColor / pow(0.475, 4.0));
 
     // Now loop through the sample rays
     vec3 v3FrontColor = vec3(0.0, 0.0, 0.0);

Specs/Scene/SkyAtmosphereSpec.js

@@ -2,6 +2,7 @@
 defineSuite([
         'Scene/SkyAtmosphere',
         'Core/Cartesian3',
+        'Core/Color',
         'Core/Ellipsoid',
         'Renderer/ClearCommand',
         'Scene/SceneMode',
@@ -11,6 +12,7 @@ defineSuite([
     ], function(
         SkyAtmosphere,
         Cartesian3,
+        Color,
         Ellipsoid,
         ClearCommand,
         SceneMode,
@@ -130,10 +132,15 @@ defineSuite([
     });
 
     it('gets ellipsoid', function() {
-        var s = new SkyAtmosphere(Ellipsoid.UNIT_SPHERE);
+        var s = new SkyAtmosphere({ellipsoid: Ellipsoid.UNIT_SPHERE});
         expect(s.ellipsoid).toEqual(Ellipsoid.UNIT_SPHERE);
     });
 
+    it('gets color', function() {
+        var s = new SkyAtmosphere({color: new Color(10,0,0)});
+        expect(s.color).toEqual(new Color(10,0,0));
+    });
+
     it('isDestroyed', function() {
         var s = new SkyAtmosphere();
         expect(s.isDestroyed()).toEqual(false);