Wrap Longitude

CHANGES.md

@@ -6,7 +6,11 @@ Beta Releases
 
 ### b14 - 2013-xx-xx
 
+* Added a line segment-ray intersection test to `IntersectionTests`.
+* Fixed an issue where a `PolylineCollection` with a model matrix other than the identity would be incorrectly rendered in 2D and Columbus view.
+
 ### b13 - 2013-02-01
+
 * Breaking changes:
    * The combined `Cesium.js` file and other required files are now created in `Build/Cesium` and `Build/CesiumUnminified` folders.
    * The Web Worker files needed when using the combined `Cesium.js` file are now in a `Workers` subdirectory.

Source/Core/IntersectionTests.js

@@ -355,5 +355,76 @@ define([
         return undefined;
     };
 
+    var lineSegmentPlaneDifference = new Cartesian3();
+
+    /**
+     * Computes the intersection of a line segment and a plane.
+     * @memberof IntersectionTests
+     *
+     * @param {Cartesian3} endPoint0 An end point of the line segment.
+     * @param {Cartesian3} endPoint1 The other end point of the line segment.
+     * @param {Cartesian3} planeNormal The plane normal.
+     * @param {Number} planeD The distance from the plane to the origin.
+     * @param {Cartesian3} [result] The object onto which to store the result.
+     * @returns {Cartesian3} The intersection point or undefined if there is no intersection.
+     *
+     * @exception {DeveloperError} endPoint0 is required.
+     * @exception {DeveloperError} endPoint1 is required.
+     * @exception {DeveloperError} planeNormal is required.
+     * @exception {DeveloperError} planeD is required.
+     *
+     * @example
+     * var origin = ellipsoid.cartographicToCartesian(Cartographic.fromDegrees(-75.59777, 40.03883, 0.0));
+     * var normal = ellipsoid.geodeticSurfaceNormal(origin);
+     * var constant = -Cartesian3.dot(normal, origin);
+     *
+     * var p0 = new Cartesian3(...);
+     * var p1 = new Cartesian3(...);
+     *
+     * // find the intersection of the line segment from p0 to p1 and the tangent plane at origin.
+     * var intersection = IntersectionTests.lineSegmentPlane(p0, p1, normal, constant);
+     */
+    IntersectionTests.lineSegmentPlane = function(endPoint0, endPoint1, planeNormal, planeD, result) {
+        if (typeof endPoint0 === 'undefined') {
+            throw new DeveloperError('endPoint0 is required.');
+        }
+
+        if (typeof endPoint1 === 'undefined') {
+            throw new DeveloperError('endPoint1 is required.');
+        }
+
+        if (typeof planeNormal === 'undefined') {
+            throw new DeveloperError('planeNormal is required.');
+        }
+
+        if (typeof planeD === 'undefined') {
+            throw new DeveloperError('planeD is required.');
+        }
+
+        var difference = Cartesian3.subtract(endPoint1, endPoint0, lineSegmentPlaneDifference);
+        var nDotDiff = Cartesian3.dot(planeNormal, difference);
+
+        // check if the segment and plane are parallel
+        if (Math.abs(nDotDiff) < CesiumMath.EPSILON6) {
+            return undefined;
+        }
+
+        var nDotP0 = Cartesian3.dot(planeNormal, endPoint0);
+        var t = -(planeD + nDotP0) / nDotDiff;
+
+        // intersection only if t is in [0, 1]
+        if (t < 0.0 || t > 1.0) {
+            return undefined;
+        }
+
+        // intersection is endPoint0 + t * (endPoint1 - endPoint0)
+        if (typeof result === 'undefined') {
+            result = new Cartesian3();
+        }
+        Cartesian3.multiplyByScalar(difference, t, result);
+        Cartesian3.add(endPoint0, result, result);
+        return result;
+    };
+
     return IntersectionTests;
 });

Source/Core/PolylinePipeline.js

@@ -1,89 +1,118 @@
 /*global define*/
-define(['./Cartographic',
-        './Cartesian3'
+define([
+        './defaultValue',
+        './Cartesian3',
+        './Cartesian4',
+        './IntersectionTests',
+        './Matrix4'
     ], function(
-        Cartographic,
-        Cartesian3) {
+        defaultValue,
+        Cartesian3,
+        Cartesian4,
+        IntersectionTests,
+        Matrix4) {
     "use strict";
 
     /**
      * DOC_TBA
      *
      * @exports PolylinePipeline
      */
-    var PolylinePipeline = {
-        /**
-         * Breaks a {@link Polyline} into segments such that it does not cross the ±180 degree meridian of an ellipsoid.
-         *
-         * @param {Ellipsoid} ellipsoid The ellipsoid to wrap around.
-         * @param {Array} positions The polyline's Cartesian positions.
-         *
-         * @returns An array of polyline segment objects containing the Cartesian and {@link Cartographic} positions and indices.
-         *
-         * @see Polyline
-         * @see PolylineCollection
-         *
-         * @example
-         * var polylines = new PolylineCollection();
-         * polylines.add(...);
-         * var positions = polylines.get(0).getPositions();
-         * var segments = PolylinePipeline.wrapLongitude(ellipsoid, positions);
-         */
-        wrapLongitude : function(ellipsoid, positions) {
-            var segments = [];
-
-            if (positions && (positions.length > 0)) {
-                var length = positions.length;
-
-                var currentSegment = [{
-                    cartesian : Cartesian3.clone(positions[0]),
-                    cartographic : ellipsoid.cartesianToCartographic(positions[0]),
-                    index : 0
-                }];
-
-                var prev = currentSegment[0].cartographic;
-
-                for ( var i = 1; i < length; ++i) {
-                    var cur = ellipsoid.cartesianToCartographic(positions[i]);
-
-                    if (Math.abs(prev.longitude - cur.longitude) > Math.PI) {
-                        var interpolatedLongitude = prev.longitude < 0.0 ? -Math.PI : Math.PI;
-                        var longitude = cur.longitude + (2.0 * interpolatedLongitude);
-                        var ratio = (interpolatedLongitude - prev.longitude) / (longitude - prev.longitude);
-                        var interpolatedLatitude = prev.latitude + (cur.latitude - prev.latitude) * ratio;
-                        var interpolatedHeight = prev.height + (cur.height - prev.height) * ratio;
+    var PolylinePipeline = {};
+
+    var wrapLongitudeInversMatrix = new Matrix4();
+    var wrapLongitudeOrigin = new Cartesian4();
+    var wrapLongitudeXZNormal = new Cartesian4();
+    var wrapLongitudeYZNormal = new Cartesian4();
+    var wrapLongitudeIntersection = new Cartesian3();
+    var wrapLongitudeOffset = new Cartesian3();
+
+    /**
+     * Breaks a {@link Polyline} into segments such that it does not cross the &plusmn;180 degree meridian of an ellipsoid.
+     * @memberof PolylinePipeline
+     *
+     * @param {Array} positions The polyline's Cartesian positions.
+     * @param {Matrix4} [modelMatrix=Matrix4.IDENTITY] The polyline's model matrix. Assumed to be an affine
+     * transformation matrix, where the upper left 3x3 elements are a rotation matrix, and
+     * the upper three elements in the fourth column are the translation.  The bottom row is assumed to be [0, 0, 0, 1].
+     * The matrix is not verified to be in the proper form.
+     *
+     * @returns An array of polyline segment objects containing the Cartesian position and indices.
+     *
+     * @see Polyline
+     * @see PolylineCollection
+     *
+     * @example
+     * var polylines = new PolylineCollection();
+     * var polyline = polylines.add(...);
+     * var positions = polyline.getPositions();
+     * var modelMatrix = polylines.modelMatrix;
+     * var segments = PolylinePipeline.wrapLongitude(positions, modelMatrix);
+     */
+    PolylinePipeline.wrapLongitude = function(positions, modelMatrix) {
+        var segments = [];
+
+        if (typeof positions !== 'undefined' && positions.length > 0) {
+            modelMatrix = defaultValue(modelMatrix, Matrix4.IDENTITY);
+            var inverseModelMatrix = Matrix4.inverseTransformation(modelMatrix, wrapLongitudeInversMatrix);
+
+            var origin = Matrix4.multiplyByPoint(inverseModelMatrix, Cartesian3.ZERO, wrapLongitudeOrigin);
+            var xzNormal = Matrix4.multiplyByVector(inverseModelMatrix, Cartesian4.UNIT_Y, wrapLongitudeXZNormal);
+            var xzConstant = -Cartesian3.dot(xzNormal, origin);
+            var yzNormal = Matrix4.multiplyByVector(inverseModelMatrix, Cartesian4.UNIT_X, wrapLongitudeYZNormal);
+            var yzConstant = -Cartesian3.dot(yzNormal, origin);
+
+            var currentSegment = [{
+                cartesian : Cartesian3.clone(positions[0]),
+                index : 0
+            }];
+            var prev = currentSegment[0].cartesian;
+
+            var length = positions.length;
+            for ( var i = 1; i < length; ++i) {
+                var cur = positions[i];
+
+                // intersects the IDL if either endpoint is on the negative side of the yz-plane
+                if (Cartesian3.dot(prev, yzNormal) + yzConstant < 0.0 || Cartesian3.dot(cur, yzNormal) + yzNormal < 0.0) {
+                    // and intersects the xz-plane
+                    var intersection = IntersectionTests.lineSegmentPlane(prev, cur, xzNormal, xzConstant, wrapLongitudeIntersection);
+                    if (typeof intersection !== 'undefined') {
+                        // move point on the xz-plane slightly away from the plane
+                        var offset = Cartesian3.multiplyByScalar(xzNormal, 5.0e-9, wrapLongitudeOffset);
+                        if (Cartesian3.dot(prev, xzNormal) + xzConstant < 0.0) {
+                            Cartesian3.negate(offset, offset);
+                        }
 
                         currentSegment.push({
-                            cartesian : ellipsoid.cartographicToCartesian(new Cartographic(interpolatedLongitude, interpolatedLatitude, interpolatedHeight)),
-                            cartographic : new Cartographic(interpolatedLongitude, interpolatedLatitude, interpolatedHeight),
+                            cartesian : Cartesian3.add(intersection, offset),
                             index : i
                         });
                         segments.push(currentSegment);
 
+                        Cartesian3.negate(offset, offset);
+
                         currentSegment = [];
                         currentSegment.push({
-                            cartesian : ellipsoid.cartographicToCartesian(new Cartographic(-interpolatedLongitude, interpolatedLatitude, interpolatedHeight)),
-                            cartographic : new Cartographic(-interpolatedLongitude, interpolatedLatitude, interpolatedHeight),
+                            cartesian : Cartesian3.add(intersection, offset),
                             index : i
                         });
                     }
-
-                    currentSegment.push({
-                        cartesian : Cartesian3.clone(positions[i]),
-                        cartographic : ellipsoid.cartesianToCartographic(positions[i]),
-                        index : i
-                    });
-
-                    prev = cur.clone();
                 }
 
-                if (currentSegment.length > 1) {
-                    segments.push(currentSegment);
-                }
+                currentSegment.push({
+                    cartesian : Cartesian3.clone(positions[i]),
+                    index : i
+                });
+
+                prev = cur;
             }
 
-            return segments;
+            if (currentSegment.length > 1) {
+                segments.push(currentSegment);
+            }
         }
+
+        return segments;
     };
 
     return PolylinePipeline;

Source/Scene/Polyline.js

@@ -361,8 +361,8 @@ define([
         return positions;
     };
 
-    Polyline.prototype._createSegments = function(ellipsoid) {
-        return PolylinePipeline.wrapLongitude(ellipsoid, this.getPositions());
+    Polyline.prototype._createSegments = function(modelMatrix) {
+        return PolylinePipeline.wrapLongitude(this.getPositions(), modelMatrix);
     };
 
     Polyline.prototype._setSegments = function(segments) {

Source/Scene/PolylineCollection.js

@@ -407,7 +407,7 @@ define([
                     var changedProperties = polyline._propertiesChanged;
                     if (changedProperties[POSITION_INDEX]) {
                         if (intersectsIDL(polyline)) {
-                            var newSegments = polyline._createSegments(this._projection._ellipsoid);
+                            var newSegments = polyline._createSegments(this.modelMatrix);
                             if (polyline._segmentsLengthChanged(newSegments)) {
                                 createVertexArrays = true;
                                 break;
@@ -1129,7 +1129,7 @@ define([
         if (this.mode === SceneMode.SCENE3D || !intersectsIDL(polyline)) {
             return polyline.getPositions().length;
         }
-        var segments = polyline._createSegments(this.ellipsoid);
+        var segments = polyline._createSegments(this.modelMatrix);
         return polyline._setSegments(segments);
     };
 

Specs/Core/IntersectionTestsSpec.js

@@ -255,4 +255,77 @@ defineSuite([
         var ray = new Ray(Cartesian3.ZERO, Cartesian3.UNIT_Z);
         expect(IntersectionTests.grazingAltitudeLocation(ray, ellipsoid)).not.toBeDefined();
     });
+
+    it('lineSegmentPlane intersects', function() {
+        var planeNormal = Cartesian3.UNIT_Y.clone();
+        var pointOnPlane = new Cartesian3(0.0, 2.0, 0.0);
+        var planeConstant = -Cartesian3.dot(planeNormal, pointOnPlane);
+
+        var endPoint0 = new Cartesian3(1.0, 1.0, 0.0);
+        var endPoint1 = new Cartesian3(1.0, 3.0, 0.0);
+
+        var intersectionPoint = IntersectionTests.lineSegmentPlane(endPoint0, endPoint1, planeNormal, planeConstant);
+
+        expect(intersectionPoint).toEqual(new Cartesian3(1.0, 2.0, 0.0));
+    });
+
+    it('lineSegmentPlane misses (entire segment behind plane)', function() {
+        var planeNormal = new Cartesian3(1.0, 0.0, 0.0);
+        var planeConstant = 0.0;
+
+        var endPoint0 = new Cartesian3(-2.0, 0.0, 0.0);
+        var endPoint1 = new Cartesian3(-5.0, 0.0, 0.0);
+
+        var intersectionPoint = IntersectionTests.lineSegmentPlane(endPoint0, endPoint1, planeNormal, planeConstant);
+
+        expect(intersectionPoint).not.toBeDefined();
+    });
+
+    it('lineSegmentPlane misses (entire segment in front of plane)', function() {
+        var planeNormal = new Cartesian3(1.0, 0.0, 0.0);
+        var planeConstant = 0.0;
+
+        var endPoint0 = new Cartesian3(5.0, 0.0, 0.0);
+        var endPoint1 = new Cartesian3(2.0, 0.0, 0.0);
+
+        var intersectionPoint = IntersectionTests.lineSegmentPlane(endPoint0, endPoint1, planeNormal, planeConstant);
+
+        expect(intersectionPoint).not.toBeDefined();
+    });
+
+    it('lineSegmentPlane misses (parallel)', function() {
+        var planeNormal = new Cartesian3(1.0, 0.0, 0.0);
+        var planeConstant = 0.0;
+
+        var endPoint0 = new Cartesian3(0.0, -1.0, 0.0);
+        var endPoint1 = new Cartesian3(0.0, 1.0, 0.0);
+
+        var intersectionPoint = IntersectionTests.lineSegmentPlane(endPoint0, endPoint1, planeNormal, planeConstant);
+
+        expect(intersectionPoint).not.toBeDefined();
+    });
+
+    it('lineSegmentPlane throws without endPoint0', function() {
+        expect(function() {
+            IntersectionTests.lineSegmentPlane();
+        }).toThrow();
+    });
+
+    it('lineSegmentPlane throws without endPoint1', function() {
+        expect(function() {
+            IntersectionTests.lineSegmentPlane(new Cartesian3());
+        }).toThrow();
+    });
+
+    it('lineSegmentPlane throws without planeNormal', function() {
+        expect(function() {
+            IntersectionTests.lineSegmentPlane(new Cartesian3(), new Cartesian3());
+        }).toThrow();
+    });
+
+    it('lineSegmentPlane throws without planeD', function() {
+        expect(function() {
+            IntersectionTests.lineSegmentPlane(new Cartesian3(), new Cartesian3(), new Cartesian3());
+        }).toThrow();
+    });
 });