Don't reproject Web Mercator imagery tiles unnecessarily

CHANGES.md

@@ -3,6 +3,7 @@ Change Log
 
 ### 1.26 - 2016-10-03
 
+* Removed an unnecessary reprojection of Web Mercator imagery tiles to the Geographic projection on load.  This should improve both visual quality and performance slightly.
 * Fixed billboard rotation when sized in meters. [#3979](https://github.com/AnalyticalGraphicsInc/cesium/issues/3979)
 * Added `DebugCameraPrimitive` to visualize the view frustum of a camera.
 * Fixed touch events for the timeline [#4305](https://github.com/AnalyticalGraphicsInc/cesium/pull/4305)

Source/Core/HeightmapTerrainData.js

@@ -89,7 +89,7 @@ define([
      *   childTileMask : childTileMask,
      *   waterMask : waterMask
      * });
-     * 
+     *
      * @see TerrainData
      * @see QuantizedMeshTerrainData
      */
@@ -198,6 +198,7 @@ define([
         var verticesPromise = taskProcessor.scheduleTask({
             heightmap : this._buffer,
             structure : structure,
+            includeWebMercatorT : true,
             width : this._width,
             height : this._height,
             nativeRectangle : nativeRectangle,
@@ -224,7 +225,7 @@ define([
                     result.maximumHeight,
                     result.boundingSphere3D,
                     result.occludeePointInScaledSpace,
-                    6,
+                    result.numberOfAttributes,
                     result.orientedBoundingBox,
                     TerrainEncoding.clone(result.encoding),
                     exaggeration);

Source/Core/HeightmapTessellator.js

@@ -15,7 +15,8 @@ define([
         './OrientedBoundingBox',
         './Rectangle',
         './TerrainEncoding',
-        './Transforms'
+        './Transforms',
+        './WebMercatorProjection',
     ], function(
         AxisAlignedBoundingBox,
         BoundingSphere,
@@ -32,7 +33,8 @@ define([
         OrientedBoundingBox,
         Rectangle,
         TerrainEncoding,
-        Transforms) {
+        Transforms,
+        WebMercatorProjection) {
     'use strict';
 
     /**
@@ -192,6 +194,7 @@ define([
 
         var relativeToCenter = defaultValue(options.relativeToCenter, Cartesian3.ZERO);
         var exaggeration = defaultValue(options.exaggeration, 1.0);
+        var includeWebMercatorT = defaultValue(options.includeWebMercatorT, false);
 
         var structure = defaultValue(options.structure, HeightmapTessellator.DEFAULT_STRUCTURE);
         var heightScale = defaultValue(structure.heightScale, HeightmapTessellator.DEFAULT_STRUCTURE.heightScale);
@@ -215,6 +218,13 @@ define([
         var fromENU = Transforms.eastNorthUpToFixedFrame(relativeToCenter, ellipsoid);
         var toENU = Matrix4.inverseTransformation(fromENU, matrix4Scratch);
 
+        var southMercatorY;
+        var oneOverMercatorHeight;
+        if (includeWebMercatorT) {
+            southMercatorY = WebMercatorProjection.geodeticLatitudeToMercatorAngle(geographicSouth);
+            oneOverMercatorHeight = 1.0 / (WebMercatorProjection.geodeticLatitudeToMercatorAngle(geographicNorth) - southMercatorY);
+        }
+
         var minimum = minimumScratch;
         minimum.x = Number.POSITIVE_INFINITY;
         minimum.y = Number.POSITIVE_INFINITY;
@@ -233,6 +243,7 @@ define([
         var positions = new Array(size);
         var heights = new Array(size);
         var uvs = new Array(size);
+        var webMercatorTs = includeWebMercatorT ? new Array(size) : [];
 
         var startRow = 0;
         var endRow = height;
@@ -272,6 +283,11 @@ define([
             var v = (latitude - geographicSouth) / (geographicNorth - geographicSouth);
             v = CesiumMath.clamp(v, 0.0, 1.0);
 
+            var webMercatorT;
+            if (includeWebMercatorT) {
+                webMercatorT = (WebMercatorProjection.geodeticLatitudeToMercatorAngle(latitude) - southMercatorY) * oneOverMercatorHeight;
+            }
+
             for (var colIndex = startCol; colIndex < endCol; ++colIndex) {
                 var col = colIndex;
                 if (col < 0) {
@@ -343,6 +359,10 @@ define([
                 u = CesiumMath.clamp(u, 0.0, 1.0);
                 uvs[index] = new Cartesian2(u, v);
 
+                if (includeWebMercatorT) {
+                    webMercatorTs[index] = webMercatorT;
+                }
+
                 index++;
 
                 Matrix4.multiplyByPoint(toENU, position, cartesian3Scratch);
@@ -369,12 +389,12 @@ define([
         }
 
         var aaBox = new AxisAlignedBoundingBox(minimum, maximum, relativeToCenter);
-        var encoding = new TerrainEncoding(aaBox, hMin, maximumHeight, fromENU, false);
+        var encoding = new TerrainEncoding(aaBox, hMin, maximumHeight, fromENU, false, includeWebMercatorT);
         var vertices = new Float32Array(size * encoding.getStride());
 
         var bufferIndex = 0;
         for (var j = 0; j < size; ++j) {
-            bufferIndex = encoding.encode(vertices, bufferIndex, positions[j], uvs[j], heights[j]);
+            bufferIndex = encoding.encode(vertices, bufferIndex, positions[j], uvs[j], heights[j], undefined, webMercatorTs[j]);
         }
 
         return {

Source/Core/QuantizedMeshTerrainData.js

@@ -104,7 +104,7 @@ define([
      *     eastSkirtHeight : 1.0,
      *     northSkirtHeight : 1.0
      * });
-     * 
+     *
      * @see TerrainData
      * @see HeightmapTerrainData
      */
@@ -273,6 +273,7 @@ define([
             maximumHeight : this._maximumHeight,
             quantizedVertices : this._quantizedVertices,
             octEncodedNormals : this._encodedNormals,
+            includeWebMercatorT : true,
             indices : this._indices,
             westIndices : this._westIndices,
             southIndices : this._southIndices,

Source/Core/Rectangle.js

@@ -597,7 +597,11 @@ define([
     };
 
     /**
-     * Computes the intersection of two rectangles
+     * Computes the intersection of two rectangles.  This function assumes that the rectangle's coordinates are
+     * latitude and longitude in radians and produces a correct intersection, taking into account the fact that
+     * the same angle can be represented with multiple values as well as the wrapping of longitude at the
+     * anti-meridian.  For a simple intersection that ignores these factors and can be used with projected
+     * coordinates, see {@link Rectangle.simpleIntersection}.
      *
      * @param {Rectangle} rectangle On rectangle to find an intersection
      * @param {Rectangle} otherRectangle Another rectangle to find an intersection
@@ -656,6 +660,47 @@ define([
         return result;
     };
 
+    /**
+     * Computes a simple intersection of two rectangles.  Unlike {@link Rectangle.intersection}, this function
+     * does not attempt to put the angular coordinates into a consistent range or to account for crossing the
+     * anti-meridian.  As such, it can be used for rectangles where the coordinates are not simply latitude
+     * and longitude (i.e. projected coordinates).
+     *
+     * @param {Rectangle} rectangle On rectangle to find an intersection
+     * @param {Rectangle} otherRectangle Another rectangle to find an intersection
+     * @param {Rectangle} [result] The object onto which to store the result.
+     * @returns {Rectangle|undefined} The modified result parameter, a new Rectangle instance if none was provided or undefined if there is no intersection.
+     */
+    Rectangle.simpleIntersection = function(rectangle, otherRectangle, result) {
+        //>>includeStart('debug', pragmas.debug);
+        if (!defined(rectangle)) {
+            throw new DeveloperError('rectangle is required');
+        }
+        if (!defined(otherRectangle)) {
+            throw new DeveloperError('otherRectangle is required.');
+        }
+        //>>includeEnd('debug');
+
+        var west = Math.max(rectangle.west, otherRectangle.west);
+        var south = Math.max(rectangle.south, otherRectangle.south);
+        var east = Math.min(rectangle.east, otherRectangle.east);
+        var north = Math.min(rectangle.north, otherRectangle.north);
+
+        if (south >= north || west >= east) {
+            return undefined;
+        }
+
+        if (!defined(result)) {
+            return new Rectangle(west, south, east, north);
+        }
+
+        result.west = west;
+        result.south = south;
+        result.east = east;
+        result.north = north;
+        return result;
+    };
+
     /**
      * Computes a rectangle that is the union of two rectangles.
      *

Source/Core/TerrainEncoding.js

@@ -4,6 +4,7 @@ define([
         './Cartesian2',
         './Cartesian3',
         './ComponentDatatype',
+        './defaultValue',
         './defined',
         './Math',
         './Matrix3',
@@ -14,6 +15,7 @@ define([
         Cartesian2,
         Cartesian3,
         ComponentDatatype,
+        defaultValue,
         defined,
         CesiumMath,
         Matrix3,
@@ -41,10 +43,11 @@ define([
      * @param {Number} maximumHeight The maximum height.
      * @param {Matrix4} fromENU The east-north-up to fixed frame matrix at the center of the terrain mesh.
      * @param {Boolean} hasVertexNormals If the mesh has vertex normals.
+     * @param {Boolean} [hasWebMercatorT=false] true if the terrain data includes a Web Mercator texture coordinate; otherwise, false.
      *
      * @private
      */
-    function TerrainEncoding(axisAlignedBoundingBox, minimumHeight, maximumHeight, fromENU, hasVertexNormals) {
+    function TerrainEncoding(axisAlignedBoundingBox, minimumHeight, maximumHeight, fromENU, hasVertexNormals, hasWebMercatorT) {
         var quantization;
         var center;
         var toENU;
@@ -137,9 +140,15 @@ define([
          * @type {Boolean}
          */
         this.hasVertexNormals = hasVertexNormals;
+
+        /**
+         * The terrain mesh contains a vertical texture coordinate following the Web Mercator projection.
+         * @type {Boolean}
+         */
+        this.hasWebMercatorT = defaultValue(hasWebMercatorT, false);
     }
 
-    TerrainEncoding.prototype.encode = function(vertexBuffer, bufferIndex, position, uv, height, normalToPack) {
+    TerrainEncoding.prototype.encode = function(vertexBuffer, bufferIndex, position, uv, height, normalToPack, webMercatorT) {
         var u = uv.x;
         var v = uv.y;
 
@@ -165,6 +174,12 @@ define([
             vertexBuffer[bufferIndex++] = compressed0;
             vertexBuffer[bufferIndex++] = compressed1;
             vertexBuffer[bufferIndex++] = compressed2;
+
+            if (this.hasWebMercatorT) {
+                Cartesian2.fromElements(webMercatorT, 0.0, cartesian2Scratch);
+                var compressed3 = AttributeCompression.compressTextureCoordinates(cartesian2Scratch);
+                vertexBuffer[bufferIndex++] = compressed3;
+            }
         } else {
             Cartesian3.subtract(position, this.center, cartesian3Scratch);
 
@@ -174,6 +189,10 @@ define([
             vertexBuffer[bufferIndex++] = height;
             vertexBuffer[bufferIndex++] = u;
             vertexBuffer[bufferIndex++] = v;
+
+            if (this.hasWebMercatorT) {
+                vertexBuffer[bufferIndex++] = webMercatorT;
+            }
         }
 
         if (this.hasVertexNormals) {
@@ -254,6 +273,10 @@ define([
                 vertexStride = 6;
         }
 
+        if (this.hasWebMercatorT) {
+            ++vertexStride;
+        }
+
         if (this.hasVertexNormals) {
             ++vertexStride;
         }
@@ -266,17 +289,29 @@ define([
         textureCoordAndEncodedNormals : 1
     };
     var attributes = {
-        compressed : 0
+        compressed0 : 0,
+        compressed1 : 1
     };
 
     TerrainEncoding.prototype.getAttributes = function(buffer) {
         var datatype = ComponentDatatype.FLOAT;
+        var sizeInBytes = ComponentDatatype.getSizeInBytes(datatype);
+        var stride;
 
         if (this.quantization === TerrainQuantization.NONE) {
-            var sizeInBytes = ComponentDatatype.getSizeInBytes(datatype);
             var position3DAndHeightLength = 4;
-            var numTexCoordComponents = this.hasVertexNormals ? 3 : 2;
-            var stride = (this.hasVertexNormals ? 7 : 6) * sizeInBytes;
+            var numTexCoordComponents = 2;
+
+            if (this.hasWebMercatorT) {
+                ++numTexCoordComponents;
+            }
+
+            if (this.hasVertexNormals) {
+                ++numTexCoordComponents;
+            }
+
+            stride = (position3DAndHeightLength + numTexCoordComponents) * sizeInBytes;
+
             return [{
                 index : attributesNone.position3DAndHeight,
                 vertexBuffer : buffer,
@@ -294,14 +329,44 @@ define([
             }];
         }
 
-        var numComponents = 3;
-        numComponents += this.hasVertexNormals ? 1 : 0;
-        return [{
-            index : attributes.compressed,
-            vertexBuffer : buffer,
-            componentDatatype : datatype,
-            componentsPerAttribute : numComponents
-        }];
+        var numCompressed0 = 3;
+        var numCompressed1 = 0;
+
+        if (this.hasWebMercatorT || this.hasVertexNormals) {
+            ++numCompressed0;
+        }
+
+        if (this.hasWebMercatorT && this.hasVertexNormals) {
+            ++numCompressed1;
+
+            stride = (numCompressed0 + numCompressed1) * sizeInBytes;
+
+            return [
+                {
+                    index : attributes.compressed0,
+                    vertexBuffer : buffer,
+                    componentDatatype : datatype,
+                    componentsPerAttribute : numCompressed0,
+                    offsetInBytes : 0,
+                    strideInBytes : stride
+                },
+                {
+                    index : attributes.compressed1,
+                    vertexBuffer : buffer,
+                    componentDatatype : datatype,
+                    componentsPerAttribute : numCompressed1,
+                    offsetInBytes : numCompressed0 * sizeInBytes,
+                    strideInBytes : stride
+                }
+            ];
+        } else {
+            return [{
+                index : attributes.compressed0,
+                vertexBuffer : buffer,
+                componentDatatype : datatype,
+                componentsPerAttribute : numCompressed0
+            }];
+        }
     };
 
     TerrainEncoding.prototype.getAttributeLocations = function() {
@@ -325,6 +390,7 @@ define([
         result.fromScaledENU = Matrix4.clone(encoding.fromScaledENU);
         result.matrix = Matrix4.clone(encoding.matrix);
         result.hasVertexNormals = encoding.hasVertexNormals;
+        result.hasWebMercatorT = encoding.hasWebMercatorT;
         return result;
     };