Extend GroundPrimitive shadow volume based on screen space error

CHANGES.md

@@ -4,6 +4,7 @@ Change Log
 ### 1.30 - 2017-02-01
 
 * Updated the morph so the default view in Columbus View is now angled. [#3878](https://github.com/AnalyticalGraphicsInc/cesium/issues/3878)
+* Fixed bug where `GroundPrimitives` where rendering incorrectly or disappearing at different zoom levels. [#4161](https://github.com/AnalyticalGraphicsInc/cesium/issues/4161) [#4326](https://github.com/AnalyticalGraphicsInc/cesium/issues/4326)
 * Fixed sky atmosphere from causing incorrect picking and hanging drill picking. [#4783](https://github.com/AnalyticalGraphicsInc/cesium/issues/4783) and [#4784](https://github.com/AnalyticalGraphicsInc/cesium/issues/4784)
 
 ### 1.29 - 2017-01-02

Source/Core/CircleGeometry.js

@@ -68,7 +68,8 @@ define([
             extrudedHeight : options.extrudedHeight,
             granularity : options.granularity,
             vertexFormat : options.vertexFormat,
-            stRotation : options.stRotation
+            stRotation : options.stRotation,
+            shadowVolume: options.shadowVolume
         };
         this._ellipseGeometry = new EllipseGeometry(ellipseGeometryOptions);
         this._workerName = 'createCircleGeometry';
@@ -113,7 +114,8 @@ define([
         vertexFormat : new VertexFormat(),
         stRotation : undefined,
         semiMajorAxis : undefined,
-        semiMinorAxis : undefined
+        semiMinorAxis : undefined,
+        shadowVolume: undefined
     };
 
     /**
@@ -133,6 +135,7 @@ define([
         scratchOptions.granularity = ellipseGeometry._granularity;
         scratchOptions.vertexFormat = VertexFormat.clone(ellipseGeometry._vertexFormat, scratchOptions.vertexFormat);
         scratchOptions.stRotation = ellipseGeometry._stRotation;
+        scratchOptions.shadowVolume = ellipseGeometry._shadowVolume;
 
         if (!defined(result)) {
             scratchOptions.radius = ellipseGeometry._semiMajorAxis;
@@ -173,7 +176,8 @@ define([
             granularity : granularity,
             extrudedHeight : minHeight,
             height : maxHeight,
-            vertexFormat : VertexFormat.POSITION_ONLY
+            vertexFormat : VertexFormat.POSITION_ONLY,
+            shadowVolume: true
         });
     };
 

Source/Core/CorridorGeometry.js

@@ -561,8 +561,8 @@ define([
 
     function computePositionsExtruded(params, vertexFormat) {
         var topVertexFormat = new VertexFormat({
-            position : vertexFormat.positon,
-            normal : (vertexFormat.normal || vertexFormat.binormal),
+            position : vertexFormat.position,
+            normal : (vertexFormat.normal || vertexFormat.binormal || params.shadowVolume),
             tangent : vertexFormat.tangent,
             binormal : (vertexFormat.normal || vertexFormat.binormal),
             st : vertexFormat.st
@@ -590,28 +590,49 @@ define([
         newPositions.set(wallPositions, length * 2);
         attributes.position.values = newPositions;
 
-        length /= 3;
+        attributes = extrudedAttributes(attributes, vertexFormat);
+        var size = length / 3;
+        if (params.shadowVolume) {
+            var topNormals = attributes.normal.values;
+            length = topNormals.length;
+
+            var extrudeNormals = new Float32Array(length * 6);
+            for (i = 0; i < length; i ++) {
+                topNormals[i] = -topNormals[i];
+            }
+            //only get normals for bottom layer that's going to be pushed down
+            extrudeNormals.set(topNormals, length); //bottom face
+            extrudeNormals = addWallPositions(topNormals, length*4, extrudeNormals); //bottom wall
+            attributes.extrudeDirection = new GeometryAttribute({
+                componentDatatype : ComponentDatatype.FLOAT,
+                componentsPerAttribute : 3,
+                values : extrudeNormals
+            });
+            if (!vertexFormat.normal) {
+                attributes.normal = undefined;
+            }
+        }
+
         var i;
         var iLength = indices.length;
-        var twoLength = length + length;
-        var newIndices = IndexDatatype.createTypedArray(newPositions.length / 3, iLength * 2 + twoLength * 3);
+        var twoSize = size + size;
+        var newIndices = IndexDatatype.createTypedArray(newPositions.length / 3, iLength * 2 + twoSize * 3);
         newIndices.set(indices);
         var index = iLength;
         for (i = 0; i < iLength; i += 3) { // bottom indices
             var v0 = indices[i];
             var v1 = indices[i + 1];
             var v2 = indices[i + 2];
-            newIndices[index++] = v2 + length;
-            newIndices[index++] = v1 + length;
-            newIndices[index++] = v0 + length;
+            newIndices[index++] = v2 + size;
+            newIndices[index++] = v1 + size;
+            newIndices[index++] = v0 + size;
         }
 
-        attributes = extrudedAttributes(attributes, vertexFormat);
         var UL, LL, UR, LR;
 
-        for (i = 0; i < twoLength; i += 2) { //wall indices
-            UL = i + twoLength;
-            LL = UL + twoLength;
+        for (i = 0; i < twoSize; i += 2) { //wall indices
+            UL = i + twoSize;
+            LL = UL + twoSize;
             UR = UL + 1;
             LR = LL + 1;
             newIndices[index++] = UL;
@@ -793,14 +814,15 @@ define([
         this._extrudedHeight = defaultValue(options.extrudedHeight, this._height);
         this._cornerType = defaultValue(options.cornerType, CornerType.ROUNDED);
         this._granularity = defaultValue(options.granularity, CesiumMath.RADIANS_PER_DEGREE);
+        this._shadowVolume = defaultValue(options.shadowVolume, false);
         this._workerName = 'createCorridorGeometry';
         this._rectangle = computeRectangle(positions, this._ellipsoid, width, this._cornerType);
 
         /**
          * The number of elements used to pack the object into an array.
          * @type {Number}
          */
-        this.packedLength = 1 + positions.length * Cartesian3.packedLength + Ellipsoid.packedLength + VertexFormat.packedLength + Rectangle.packedLength + 5;
+        this.packedLength = 1 + positions.length * Cartesian3.packedLength + Ellipsoid.packedLength + VertexFormat.packedLength + Rectangle.packedLength + 6;
     }
 
     /**
@@ -845,7 +867,8 @@ define([
         array[startingIndex++] = value._height;
         array[startingIndex++] = value._extrudedHeight;
         array[startingIndex++] = value._cornerType;
-        array[startingIndex]   = value._granularity;
+        array[startingIndex++] = value._granularity;
+        array[startingIndex] = value._shadowVolume ? 1.0 : 0.0;
 
         return array;
     };
@@ -861,7 +884,8 @@ define([
         height : undefined,
         extrudedHeight : undefined,
         cornerType : undefined,
-        granularity : undefined
+        granularity : undefined,
+        shadowVolume: undefined
     };
 
     /**
@@ -901,7 +925,8 @@ define([
         var height = array[startingIndex++];
         var extrudedHeight = array[startingIndex++];
         var cornerType = array[startingIndex++];
-        var granularity = array[startingIndex];
+        var granularity = array[startingIndex++];
+        var shadowVolume = array[startingIndex] === 1.0;
 
         if (!defined(result)) {
             scratchOptions.positions = positions;
@@ -910,6 +935,7 @@ define([
             scratchOptions.extrudedHeight = extrudedHeight;
             scratchOptions.cornerType = cornerType;
             scratchOptions.granularity = granularity;
+            scratchOptions.shadowVolume = shadowVolume;
             return new CorridorGeometry(scratchOptions);
         }
 
@@ -922,6 +948,7 @@ define([
         result._cornerType = cornerType;
         result._granularity = granularity;
         result._rectangle = Rectangle.clone(rectangle);
+        result._shadowVolume = shadowVolume;
 
         return result;
     };
@@ -962,6 +989,7 @@ define([
             height = h;
             params.height = height;
             params.extrudedHeight = extrudedHeight;
+            params.shadowVolume = corridorGeometry._shadowVolume;
             attr = computePositionsExtruded(params, vertexFormat);
         } else {
             var computedPositions = CorridorGeometryLibrary.computePositions(params);
@@ -1000,7 +1028,8 @@ define([
             granularity : granularity,
             extrudedHeight : minHeight,
             height : maxHeight,
-            vertexFormat : VertexFormat.POSITION_ONLY
+            vertexFormat : VertexFormat.POSITION_ONLY,
+            shadowVolume: true
         });
     };