Cesium3DTileBatchTable.js

define([
        '../Core/arrayFill',
        '../Core/Cartesian2',
        '../Core/Cartesian4',
        '../Core/Check',
        '../Core/clone',
        '../Core/Color',
        '../Core/combine',
        '../Core/ComponentDatatype',
        '../Core/defaultValue',
        '../Core/defined',
        '../Core/defineProperties',
        '../Core/deprecationWarning',
        '../Core/destroyObject',
        '../Core/DeveloperError',
        '../Core/Math',
        '../Core/PixelFormat',
        '../Core/RuntimeError',
        '../Renderer/ContextLimits',
        '../Renderer/DrawCommand',
        '../Renderer/Pass',
        '../Renderer/PixelDatatype',
        '../Renderer/RenderState',
        '../Renderer/Sampler',
        '../Renderer/ShaderSource',
        '../Renderer/Texture',
        '../Renderer/TextureMagnificationFilter',
        '../Renderer/TextureMinificationFilter',
        './AttributeType',
        './BlendingState',
        './Cesium3DTileColorBlendMode',
        './CullFace',
        './getBinaryAccessor',
        './StencilFunction',
        './StencilOperation'
    ], function(
        arrayFill,
        Cartesian2,
        Cartesian4,
        Check,
        clone,
        Color,
        combine,
        ComponentDatatype,
        defaultValue,
        defined,
        defineProperties,
        deprecationWarning,
        destroyObject,
        DeveloperError,
        CesiumMath,
        PixelFormat,
        RuntimeError,
        ContextLimits,
        DrawCommand,
        Pass,
        PixelDatatype,
        RenderState,
        Sampler,
        ShaderSource,
        Texture,
        TextureMagnificationFilter,
        TextureMinificationFilter,
        AttributeType,
        BlendingState,
        Cesium3DTileColorBlendMode,
        CullFace,
        getBinaryAccessor,
        StencilFunction,
        StencilOperation) {
    'use strict';

    var DEFAULT_COLOR_VALUE = Color.WHITE;
    var DEFAULT_SHOW_VALUE = true;

    /**
     * @private
     */
    function Cesium3DTileBatchTable(content, featuresLength, batchTableJson, batchTableBinary, colorChangedCallback) {
        /**
         * @readonly
         */
        this.featuresLength = featuresLength;

        this._translucentFeaturesLength = 0; // Number of features in the tile that are translucent

        var extensions;
        if (defined(batchTableJson)) {
            extensions = batchTableJson.extensions;
        }
        this._extensions = defaultValue(extensions, {});

        var properties = initializeProperties(batchTableJson);
        this._properties = properties;

        this._batchTableHierarchy = initializeHierarchy(this, batchTableJson, batchTableBinary);
        this._batchTableBinaryProperties = getBinaryProperties(featuresLength, properties, batchTableBinary);

        // PERFORMANCE_IDEA: These parallel arrays probably generate cache misses in get/set color/show
        // and use A LOT of memory.  How can we use less memory?
        this._showAlphaProperties = undefined; // [Show (0 or 255), Alpha (0 to 255)] property for each feature
        this._batchValues = undefined;  // Per-feature RGBA (A is based on the color's alpha and feature's show property)

        this._batchValuesDirty = false;
        this._batchTexture = undefined;
        this._defaultTexture = undefined;

        this._pickTexture = undefined;
        this._pickIds = [];

        this._content = content;

        this._colorChangedCallback = colorChangedCallback;

        // Dimensions for batch and pick textures
        var textureDimensions;
        var textureStep;

        if (featuresLength > 0) {
            // PERFORMANCE_IDEA: this can waste memory in the last row in the uncommon case
            // when more than one row is needed (e.g., > 16K features in one tile)
            var width = Math.min(featuresLength, ContextLimits.maximumTextureSize);
            var height = Math.ceil(featuresLength / ContextLimits.maximumTextureSize);
            var stepX = 1.0 / width;
            var centerX = stepX * 0.5;
            var stepY = 1.0 / height;
            var centerY = stepY * 0.5;

            textureDimensions = new Cartesian2(width, height);
            textureStep = new Cartesian4(stepX, centerX, stepY, centerY);
        }

        this._textureDimensions = textureDimensions;
        this._textureStep = textureStep;
    }

    // This can be overridden for testing purposes
    Cesium3DTileBatchTable._deprecationWarning = deprecationWarning;

    defineProperties(Cesium3DTileBatchTable.prototype, {
        memorySizeInBytes : {
            get : function() {
                var memory = 0;
                if (defined(this._pickTexture)) {
                    memory += this._pickTexture.sizeInBytes;
                }
                if (defined(this._batchTexture)) {
                    memory += this._batchTexture.sizeInBytes;
                }
                return memory;
            }
        }
    });

    function initializeProperties(jsonHeader) {
        var properties = {};

        if (!defined(jsonHeader)) {
            return properties;
        }

        for (var propertyName in jsonHeader) {
            if (jsonHeader.hasOwnProperty(propertyName)
                    && propertyName !== 'HIERARCHY' // Deprecated HIERARCHY property
                    && propertyName !== 'extensions'
                    && propertyName !== 'extras') {
                properties[propertyName] = clone(jsonHeader[propertyName], true);
            }
        }

        return properties;
    }

    function initializeHierarchy(batchTable, jsonHeader, binaryBody) {
        if (!defined(jsonHeader)) {
            return;
        }

        var hierarchy = batchTable._extensions['3DTILES_batch_table_hierarchy'];

        var legacyHierarchy = jsonHeader.HIERARCHY;
        if (defined(legacyHierarchy)) {
            Cesium3DTileBatchTable._deprecationWarning('batchTableHierarchyExtension', 'The batch table HIERARCHY property has been moved to an extension. Use extensions.3DTILES_batch_table_hierarchy instead.');
            batchTable._extensions['3DTILES_batch_table_hierarchy'] = legacyHierarchy;
            hierarchy = legacyHierarchy;
        }

        if (!defined(hierarchy)) {
            return;
        }

        return initializeHierarchyValues(hierarchy, binaryBody);
    }

    function initializeHierarchyValues(hierarchyJson, binaryBody) {
        var i;
        var classId;
        var binaryAccessor;

        var instancesLength = hierarchyJson.instancesLength;
        var classes = hierarchyJson.classes;
        var classIds = hierarchyJson.classIds;
        var parentCounts = hierarchyJson.parentCounts;
        var parentIds = hierarchyJson.parentIds;
        var parentIdsLength = instancesLength;

        if (defined(classIds.byteOffset)) {
            classIds.componentType = defaultValue(classIds.componentType, ComponentDatatype.UNSIGNED_SHORT);
            classIds.type = AttributeType.SCALAR;
            binaryAccessor = getBinaryAccessor(classIds);
            classIds = binaryAccessor.createArrayBufferView(binaryBody.buffer, binaryBody.byteOffset + classIds.byteOffset, instancesLength);
        }

        var parentIndexes;
        if (defined(parentCounts)) {
            if (defined(parentCounts.byteOffset)) {
                parentCounts.componentType = defaultValue(parentCounts.componentType, ComponentDatatype.UNSIGNED_SHORT);
                parentCounts.type = AttributeType.SCALAR;
                binaryAccessor = getBinaryAccessor(parentCounts);
                parentCounts = binaryAccessor.createArrayBufferView(binaryBody.buffer, binaryBody.byteOffset + parentCounts.byteOffset, instancesLength);
            }
            parentIndexes = new Uint16Array(instancesLength);
            parentIdsLength = 0;
            for (i = 0; i < instancesLength; ++i) {
                parentIndexes[i] = parentIdsLength;
                parentIdsLength += parentCounts[i];
            }
        }

        if (defined(parentIds) && defined(parentIds.byteOffset)) {
            parentIds.componentType = defaultValue(parentIds.componentType, ComponentDatatype.UNSIGNED_SHORT);
            parentIds.type = AttributeType.SCALAR;
            binaryAccessor = getBinaryAccessor(parentIds);
            parentIds = binaryAccessor.createArrayBufferView(binaryBody.buffer, binaryBody.byteOffset + parentIds.byteOffset, parentIdsLength);
        }

        var classesLength = classes.length;
        for (i = 0; i < classesLength; ++i) {
            var classInstancesLength = classes[i].length;
            var properties = classes[i].instances;
            var binaryProperties = getBinaryProperties(classInstancesLength, properties, binaryBody);
            classes[i].instances = combine(binaryProperties, properties);
        }

        var classCounts = arrayFill(new Array(classesLength), 0);
        var classIndexes = new Uint16Array(instancesLength);
        for (i = 0; i < instancesLength; ++i) {
            classId = classIds[i];
            classIndexes[i] = classCounts[classId];
            ++classCounts[classId];
        }

        var hierarchy = {
            classes : classes,
            classIds : classIds,
            classIndexes : classIndexes,
            parentCounts : parentCounts,
            parentIndexes : parentIndexes,
            parentIds : parentIds
        };

        //>>includeStart('debug', pragmas.debug);
        validateHierarchy(hierarchy);
        //>>includeEnd('debug');

        return hierarchy;
    }

    //>>includeStart('debug', pragmas.debug);
    var scratchValidateStack = [];
    function validateHierarchy(hierarchy) {
        var stack = scratchValidateStack;
        stack.length = 0;

        var classIds = hierarchy.classIds;
        var instancesLength = classIds.length;

        for (var i = 0; i < instancesLength; ++i) {
            validateInstance(hierarchy, i, stack);
        }
    }

    function validateInstance(hierarchy, instanceIndex, stack) {
        var parentCounts = hierarchy.parentCounts;
        var parentIds = hierarchy.parentIds;
        var parentIndexes = hierarchy.parentIndexes;
        var classIds = hierarchy.classIds;
        var instancesLength = classIds.length;

        if (!defined(parentIds)) {
            // No need to validate if there are no parents
            return;
        }

        if (instanceIndex >= instancesLength) {
            throw new DeveloperError('Parent index ' + instanceIndex + ' exceeds the total number of instances: ' + instancesLength);
        }
        if (stack.indexOf(instanceIndex) > -1) {
            throw new DeveloperError('Circular dependency detected in the batch table hierarchy.');
        }

        stack.push(instanceIndex);
        var parentCount = defined(parentCounts) ? parentCounts[instanceIndex] : 1;
        var parentIndex = defined(parentCounts) ? parentIndexes[instanceIndex] : instanceIndex;
        for (var i = 0; i < parentCount; ++i) {
            var parentId = parentIds[parentIndex + i];
            // Stop the traversal when the instance has no parent (its parentId equals itself), else continue the traversal.
            if (parentId !== instanceIndex) {
                validateInstance(hierarchy, parentId, stack);
            }
        }
        stack.pop(instanceIndex);
    }
    //>>includeEnd('debug');

    function getBinaryProperties(featuresLength, properties, binaryBody) {
        var binaryProperties;
        for (var name in properties) {
            if (properties.hasOwnProperty(name)) {
                var property = properties[name];
                var byteOffset = property.byteOffset;
                if (defined(byteOffset)) {
                    // This is a binary property
                    var componentType = property.componentType;
                    var type = property.type;
                    if (!defined(componentType)) {
                        throw new RuntimeError('componentType is required.');
                    }
                    if (!defined(type)) {
                        throw new RuntimeError('type is required.');
                    }
                    if (!defined(binaryBody)) {
                        throw new RuntimeError('Property ' + name + ' requires a batch table binary.');
                    }

                    var binaryAccessor = getBinaryAccessor(property);
                    var componentCount = binaryAccessor.componentsPerAttribute;
                    var classType = binaryAccessor.classType;
                    var typedArray = binaryAccessor.createArrayBufferView(binaryBody.buffer, binaryBody.byteOffset + byteOffset, featuresLength);

                    if (!defined(binaryProperties)) {
                        binaryProperties = {};
                    }

                    // Store any information needed to access the binary data, including the typed array,
                    // componentCount (e.g. a VEC4 would be 4), and the type used to pack and unpack (e.g. Cartesian4).
                    binaryProperties[name] = {
                        typedArray : typedArray,
                        componentCount : componentCount,
                        type : classType
                    };
                }
            }
        }
        return binaryProperties;
    }

    Cesium3DTileBatchTable.getBinaryProperties = function(featuresLength, batchTableJson, batchTableBinary) {
        return getBinaryProperties(featuresLength, batchTableJson, batchTableBinary);
    };

    function getByteLength(batchTable) {
        var dimensions = batchTable._textureDimensions;
        return (dimensions.x * dimensions.y) * 4;
    }

    function getBatchValues(batchTable) {
        if (!defined(batchTable._batchValues)) {
            // Default batch texture to RGBA = 255: white highlight (RGB) and show/alpha = true/255 (A).
            var byteLength = getByteLength(batchTable);
            var bytes = new Uint8Array(byteLength);
            arrayFill(bytes, 255);
            batchTable._batchValues = bytes;
        }

        return batchTable._batchValues;
    }

    function getShowAlphaProperties(batchTable) {
        if (!defined(batchTable._showAlphaProperties)) {
            var byteLength = 2 * batchTable.featuresLength;
            var bytes = new Uint8Array(byteLength);
            // [Show = true, Alpha = 255]
            arrayFill(bytes, 255);
            batchTable._showAlphaProperties = bytes;
        }
        return batchTable._showAlphaProperties;
    }

    function checkBatchId(batchId, featuresLength) {
        if (!defined(batchId) || (batchId < 0) || (batchId > featuresLength)) {
            throw new DeveloperError('batchId is required and between zero and featuresLength - 1 (' + featuresLength - + ').');
        }
    }

    Cesium3DTileBatchTable.prototype.setShow = function(batchId, show) {
        //>>includeStart('debug', pragmas.debug);
        checkBatchId(batchId, this.featuresLength);
        Check.typeOf.bool('show', show);
        //>>includeEnd('debug');

        if (show && !defined(this._showAlphaProperties)) {
            // Avoid allocating since the default is show = true
            return;
        }

        var showAlphaProperties = getShowAlphaProperties(this);
        var propertyOffset = batchId * 2;

        var newShow = show ? 255 : 0;
        if (showAlphaProperties[propertyOffset] !== newShow) {
            showAlphaProperties[propertyOffset] = newShow;

            var batchValues = getBatchValues(this);

            // Compute alpha used in the shader based on show and color.alpha properties
            var offset = (batchId * 4) + 3;
            batchValues[offset] = show ? showAlphaProperties[propertyOffset + 1] : 0;

            this._batchValuesDirty = true;
        }
    };

    Cesium3DTileBatchTable.prototype.setAllShow = function(show) {
        //>>includeStart('debug', pragmas.debug);
        Check.typeOf.bool('show', show);
        //>>includeEnd('debug');

        var featuresLength = this.featuresLength;
        for (var i = 0; i < featuresLength; ++i) {
            this.setShow(i, show);
        }
    };

    Cesium3DTileBatchTable.prototype.getShow = function(batchId) {
        //>>includeStart('debug', pragmas.debug);
        checkBatchId(batchId, this.featuresLength);
        //>>includeEnd('debug');

        if (!defined(this._showAlphaProperties)) {
            // Avoid allocating since the default is show = true
            return true;
        }

        var offset = batchId * 2;
        return (this._showAlphaProperties[offset] === 255);
    };

    var scratchColorBytes = new Array(4);

    Cesium3DTileBatchTable.prototype.setColor = function(batchId, color) {
        //>>includeStart('debug', pragmas.debug);
        checkBatchId(batchId, this.featuresLength);
        Check.typeOf.object('color', color);
        //>>includeEnd('debug');

        if (Color.equals(color, DEFAULT_COLOR_VALUE) && !defined(this._batchValues)) {
            // Avoid allocating since the default is white
            return;
        }

        var newColor = color.toBytes(scratchColorBytes);
        var newAlpha = newColor[3];

        var batchValues = getBatchValues(this);
        var offset = batchId * 4;

        var showAlphaProperties = getShowAlphaProperties(this);
        var propertyOffset = batchId * 2;

        if ((batchValues[offset] !== newColor[0]) ||
            (batchValues[offset + 1] !== newColor[1]) ||
            (batchValues[offset + 2] !== newColor[2]) ||
            (showAlphaProperties[propertyOffset + 1] !== newAlpha)) {

            batchValues[offset] = newColor[0];
            batchValues[offset + 1] = newColor[1];
            batchValues[offset + 2] = newColor[2];

            var wasTranslucent = (showAlphaProperties[propertyOffset + 1] !== 255);

            // Compute alpha used in the shader based on show and color.alpha properties
            var show = showAlphaProperties[propertyOffset] !== 0;
            batchValues[offset + 3] = show ? newAlpha : 0;
            showAlphaProperties[propertyOffset + 1] = newAlpha;

            // Track number of translucent features so we know if this tile needs
            // opaque commands, translucent commands, or both for rendering.
            var isTranslucent = (newAlpha !== 255);
            if (isTranslucent && !wasTranslucent) {
                ++this._translucentFeaturesLength;
            } else if (!isTranslucent && wasTranslucent) {
                --this._translucentFeaturesLength;
            }

            this._batchValuesDirty = true;

            if (defined(this._colorChangedCallback)) {
                this._colorChangedCallback(batchId, color);
            }
        }
    };

    Cesium3DTileBatchTable.prototype.setAllColor = function(color) {
        //>>includeStart('debug', pragmas.debug);
        Check.typeOf.object('color', color);
        //>>includeEnd('debug');

        var featuresLength = this.featuresLength;
        for (var i = 0; i < featuresLength; ++i) {
            this.setColor(i, color);
        }
    };

    Cesium3DTileBatchTable.prototype.getColor = function(batchId, result) {
        //>>includeStart('debug', pragmas.debug);
        checkBatchId(batchId, this.featuresLength);
        Check.typeOf.object('result', result);
        //>>includeEnd('debug');

        if (!defined(this._batchValues)) {
            return Color.clone(DEFAULT_COLOR_VALUE, result);
        }

        var batchValues = this._batchValues;
        var offset = batchId * 4;

        var showAlphaProperties = this._showAlphaProperties;
        var propertyOffset = batchId * 2;

        return Color.fromBytes(batchValues[offset],
            batchValues[offset + 1],
            batchValues[offset + 2],
            showAlphaProperties[propertyOffset + 1],
            result);
    };

    Cesium3DTileBatchTable.prototype.getPickColor = function(batchId) {
        //>>includeStart('debug', pragmas.debug);
        checkBatchId(batchId, this.featuresLength);
        //>>includeEnd('debug');
        return this._pickIds[batchId];
    };

    var scratchColor = new Color();

    Cesium3DTileBatchTable.prototype.applyStyle = function(frameState, style) {
        if (!defined(style)) {
            this.setAllColor(DEFAULT_COLOR_VALUE);
            this.setAllShow(true);
            return;
        }

        var content = this._content;
        var length = this.featuresLength;
        for (var i = 0; i < length; ++i) {
            var feature = content.getFeature(i);
            var color = defined(style.color) ? style.color.evaluateColor(frameState, feature, scratchColor) : DEFAULT_COLOR_VALUE;
            var show = defined(style.show) ? style.show.evaluate(frameState, feature) : DEFAULT_SHOW_VALUE;
            this.setColor(i, color);
            this.setShow(i, show);
        }
    };

    function getBinaryProperty(binaryProperty, index) {
        var typedArray = binaryProperty.typedArray;
        var componentCount = binaryProperty.componentCount;
        if (componentCount === 1) {
            return typedArray[index];
        }
        return binaryProperty.type.unpack(typedArray, index * componentCount);
    }

    function setBinaryProperty(binaryProperty, index, value) {
        var typedArray = binaryProperty.typedArray;
        var componentCount = binaryProperty.componentCount;
        if (componentCount === 1) {
            typedArray[index] = value;
        } else {
            binaryProperty.type.pack(value, typedArray, index * componentCount);
        }
    }

    // The size of this array equals the maximum instance count among all loaded tiles, which has the potential to be large.
    var scratchVisited = [];
    var scratchStack = [];
    var marker = 0;
    function traverseHierarchyMultipleParents(hierarchy, instanceIndex, endConditionCallback) {
        var classIds = hierarchy.classIds;
        var parentCounts = hierarchy.parentCounts;
        var parentIds = hierarchy.parentIds;
        var parentIndexes = hierarchy.parentIndexes;
        var instancesLength = classIds.length;

        // Ignore instances that have already been visited. This occurs in diamond inheritance situations.
        // Use a marker value to indicate that an instance has been visited, which increments with each run.
        // This is more efficient than clearing the visited array every time.
        var visited = scratchVisited;
        visited.length = Math.max(visited.length, instancesLength);
        var visitedMarker = ++marker;

        var stack = scratchStack;
        stack.length = 0;
        stack.push(instanceIndex);

        while (stack.length > 0) {
            instanceIndex = stack.pop();
            if (visited[instanceIndex] === visitedMarker) {
                // This instance has already been visited, stop traversal
                continue;
            }
            visited[instanceIndex] = visitedMarker;
            var result = endConditionCallback(hierarchy, instanceIndex);
            if (defined(result)) {
                // The end condition was met, stop the traversal and return the result
                return result;
            }
            var parentCount = parentCounts[instanceIndex];
            var parentIndex = parentIndexes[instanceIndex];
            for (var i = 0; i < parentCount; ++i) {
                var parentId = parentIds[parentIndex + i];
                // Stop the traversal when the instance has no parent (its parentId equals itself)
                // else add the parent to the stack to continue the traversal.
                if (parentId !== instanceIndex) {
                    stack.push(parentId);
                }
            }
        }
    }

    function traverseHierarchySingleParent(hierarchy, instanceIndex, endConditionCallback) {
        var hasParent = true;
        while (hasParent) {
            var result = endConditionCallback(hierarchy, instanceIndex);
            if (defined(result)) {
                // The end condition was met, stop the traversal and return the result
                return result;
            }
            var parentId = hierarchy.parentIds[instanceIndex];
            hasParent = parentId !== instanceIndex;
            instanceIndex = parentId;
        }
    }

    function traverseHierarchy(hierarchy, instanceIndex, endConditionCallback) {
        // Traverse over the hierarchy and process each instance with the endConditionCallback.
        // When the endConditionCallback returns a value, the traversal stops and that value is returned.
        var parentCounts = hierarchy.parentCounts;
        var parentIds = hierarchy.parentIds;
        if (!defined(parentIds)) {
            return endConditionCallback(hierarchy, instanceIndex);
        } else if (defined(parentCounts)) {
            return traverseHierarchyMultipleParents(hierarchy, instanceIndex, endConditionCallback);
        }
        return traverseHierarchySingleParent(hierarchy, instanceIndex, endConditionCallback);
    }

    function hasPropertyInHierarchy(batchTable, batchId, name) {
        var hierarchy = batchTable._batchTableHierarchy;
        var result = traverseHierarchy(hierarchy, batchId, function(hierarchy, instanceIndex) {
            var classId = hierarchy.classIds[instanceIndex];
            var instances = hierarchy.classes[classId].instances;
            if (defined(instances[name])) {
                return true;
            }
        });
        return defined(result);
    }

    function getPropertyNamesInHierarchy(batchTable, batchId, results) {
        var hierarchy = batchTable._batchTableHierarchy;
        traverseHierarchy(hierarchy, batchId, function(hierarchy, instanceIndex) {
            var classId = hierarchy.classIds[instanceIndex];
            var instances = hierarchy.classes[classId].instances;
            for (var name in instances) {
                if (instances.hasOwnProperty(name)) {
                    if (results.indexOf(name) === -1) {
                        results.push(name);
                    }
                }
            }
        });
    }

    function getHierarchyProperty(batchTable, batchId, name) {
        var hierarchy = batchTable._batchTableHierarchy;
        return traverseHierarchy(hierarchy, batchId, function(hierarchy, instanceIndex) {
            var classId = hierarchy.classIds[instanceIndex];
            var instanceClass = hierarchy.classes[classId];
            var indexInClass = hierarchy.classIndexes[instanceIndex];
            var propertyValues = instanceClass.instances[name];
            if (defined(propertyValues)) {
                if (defined(propertyValues.typedArray)) {
                    return getBinaryProperty(propertyValues, indexInClass);
                }
                return clone(propertyValues[indexInClass], true);
            }
        });
    }

    function setHierarchyProperty(batchTable, batchId, name, value) {
        var hierarchy = batchTable._batchTableHierarchy;
        var result = traverseHierarchy(hierarchy, batchId, function(hierarchy, instanceIndex) {
            var classId = hierarchy.classIds[instanceIndex];
            var instanceClass = hierarchy.classes[classId];
            var indexInClass = hierarchy.classIndexes[instanceIndex];
            var propertyValues = instanceClass.instances[name];
            if (defined(propertyValues)) {
                //>>includeStart('debug', pragmas.debug);
                if (instanceIndex !== batchId) {
                    throw new DeveloperError('Inherited property "' + name + '" is read-only.');
                }
                //>>includeEnd('debug');
                if (defined(propertyValues.typedArray)) {
                    setBinaryProperty(propertyValues, indexInClass, value);
                } else {
                    propertyValues[indexInClass] = clone(value, true);
                }
                return true;
            }
        });
        return defined(result);
    }

    Cesium3DTileBatchTable.prototype.isClass = function(batchId, className) {
        //>>includeStart('debug', pragmas.debug);
        checkBatchId(batchId, this.featuresLength);
        Check.typeOf.string('className', className);
        //>>includeEnd('debug');

        // PERFORMANCE_IDEA : cache results in the ancestor classes to speed up this check if this area becomes a hotspot
        var hierarchy = this._batchTableHierarchy;
        if (!defined(hierarchy)) {
            return false;
        }

        // PERFORMANCE_IDEA : treat class names as integers for faster comparisons
        var result = traverseHierarchy(hierarchy, batchId, function(hierarchy, instanceIndex) {
            var classId = hierarchy.classIds[instanceIndex];
            var instanceClass = hierarchy.classes[classId];
            if (instanceClass.name === className) {
                return true;
            }
        });
        return defined(result);
    };

    Cesium3DTileBatchTable.prototype.isExactClass = function(batchId, className) {
        //>>includeStart('debug', pragmas.debug);
        Check.typeOf.string('className', className);
        //>>includeEnd('debug');

        return (this.getExactClassName(batchId) === className);
    };

    Cesium3DTileBatchTable.prototype.getExactClassName = function(batchId) {
        //>>includeStart('debug', pragmas.debug);
        checkBatchId(batchId, this.featuresLength);
        //>>includeEnd('debug');

        var hierarchy = this._batchTableHierarchy;
        if (!defined(hierarchy)) {
            return undefined;
        }
        var classId = hierarchy.classIds[batchId];
        var instanceClass = hierarchy.classes[classId];
        return instanceClass.name;
    };

    Cesium3DTileBatchTable.prototype.hasProperty = function(batchId, name) {
        //>>includeStart('debug', pragmas.debug);
        checkBatchId(batchId, this.featuresLength);
        Check.typeOf.string('name', name);
        //>>includeEnd('debug');

        return (defined(this._properties[name])) || (defined(this._batchTableHierarchy) && hasPropertyInHierarchy(this, batchId, name));
    };

    Cesium3DTileBatchTable.prototype.getPropertyNames = function(batchId, results) {
        //>>includeStart('debug', pragmas.debug);
        checkBatchId(batchId, this.featuresLength);
        //>>includeEnd('debug');

        results = defined(results) ? results : [];
        results.length = 0;

        var propertyNames = Object.keys(this._properties);
        results.push.apply(results, propertyNames);

        if (defined(this._batchTableHierarchy)) {
            getPropertyNamesInHierarchy(this, batchId, results);
        }

        return results;
    };

    Cesium3DTileBatchTable.prototype.getProperty = function(batchId, name) {
        //>>includeStart('debug', pragmas.debug);
        checkBatchId(batchId, this.featuresLength);
        Check.typeOf.string('name', name);
        //>>includeEnd('debug');

        if (defined(this._batchTableBinaryProperties)) {
            var binaryProperty = this._batchTableBinaryProperties[name];
            if (defined(binaryProperty)) {
                return getBinaryProperty(binaryProperty, batchId);
            }
        }

        var propertyValues = this._properties[name];
        if (defined(propertyValues)) {
            return clone(propertyValues[batchId], true);
        }

        if (defined(this._batchTableHierarchy)) {
            var hierarchyProperty = getHierarchyProperty(this, batchId, name);
            if (defined(hierarchyProperty)) {
                return hierarchyProperty;
            }
        }

        return undefined;
    };

    Cesium3DTileBatchTable.prototype.setProperty = function(batchId, name, value) {
        var featuresLength = this.featuresLength;
        //>>includeStart('debug', pragmas.debug);
        checkBatchId(batchId, featuresLength);
        Check.typeOf.string('name', name);
        //>>includeEnd('debug');

        if (defined(this._batchTableBinaryProperties)) {
            var binaryProperty = this._batchTableBinaryProperties[name];
            if (defined(binaryProperty)) {
                setBinaryProperty(binaryProperty, batchId, value);
                return;
            }
        }

        if (defined(this._batchTableHierarchy)) {
            if (setHierarchyProperty(this, batchId, name, value)) {
                return;
            }
        }

        var propertyValues = this._properties[name];
        if (!defined(propertyValues)) {
            // Property does not exist. Create it.
            this._properties[name] = new Array(featuresLength);
            propertyValues = this._properties[name];
        }

        propertyValues[batchId] = clone(value, true);
    };

    function getGlslComputeSt(batchTable) {
        // GLSL batchId is zero-based: [0, featuresLength - 1]
        if (batchTable._textureDimensions.y === 1) {
            return 'uniform vec4 tile_textureStep; \n' +
                'vec2 computeSt(float batchId) \n' +
                '{ \n' +
                '    float stepX = tile_textureStep.x; \n' +
                '    float centerX = tile_textureStep.y; \n' +
                '    return vec2(centerX + (batchId * stepX), 0.5); \n' +
                '} \n';
        }

        return 'uniform vec4 tile_textureStep; \n' +
            'uniform vec2 tile_textureDimensions; \n' +
            'vec2 computeSt(float batchId) \n' +
            '{ \n' +
            '    float stepX = tile_textureStep.x; \n' +
            '    float centerX = tile_textureStep.y; \n' +
            '    float stepY = tile_textureStep.z; \n' +
            '    float centerY = tile_textureStep.w; \n' +
            '    float xId = mod(batchId, tile_textureDimensions.x); \n' +
            '    float yId = floor(batchId / tile_textureDimensions.x); \n' +
            '    return vec2(centerX + (xId * stepX), centerY + (yId * stepY)); \n' +
            '} \n';
    }

    Cesium3DTileBatchTable.prototype.getVertexShaderCallback = function(handleTranslucent, batchIdAttributeName, diffuseAttributeOrUniformName) {
        if (this.featuresLength === 0) {
            return;
        }

        var that = this;
        return function(source) {
            // If the color blend mode is HIGHLIGHT, the highlight color will always be applied in the fragment shader.
            // No need to apply the highlight color in the vertex shader as well.
            var renamedSource = modifyDiffuse(source, diffuseAttributeOrUniformName, false);
            var newMain;

            if (ContextLimits.maximumVertexTextureImageUnits > 0) {
                // When VTF is supported, perform per-feature show/hide in the vertex shader
                newMain = '';
                if (handleTranslucent) {
                    newMain += 'uniform bool tile_translucentCommand; \n';
                }
                newMain +=
                    'uniform sampler2D tile_batchTexture; \n' +
                    'varying vec4 tile_featureColor; \n' +
                    'varying vec2 tile_featureSt; \n' +
                    'void main() \n' +
                    '{ \n' +
                    '    vec2 st = computeSt(' + batchIdAttributeName + '); \n' +
                    '    vec4 featureProperties = texture2D(tile_batchTexture, st); \n' +
                    '    tile_color(featureProperties); \n' +
                    '    float show = ceil(featureProperties.a); \n' +      // 0 - false, non-zeo - true
                    '    gl_Position *= show; \n';                          // Per-feature show/hide
                if (handleTranslucent) {
                    newMain +=
                        '    bool isStyleTranslucent = (featureProperties.a != 1.0); \n' +
                        '    if (czm_pass == czm_passTranslucent) \n' +
                        '    { \n' +
                        '        if (!isStyleTranslucent && !tile_translucentCommand) \n' + // Do not render opaque features in the translucent pass
                        '        { \n' +
                        '            gl_Position *= 0.0; \n' +
                        '        } \n' +
                        '    } \n' +
                        '    else \n' +
                        '    { \n' +
                        '        if (isStyleTranslucent) \n' + // Do not render translucent features in the opaque pass
                        '        { \n' +
                        '            gl_Position *= 0.0; \n' +
                        '        } \n' +
                        '    } \n';
                }
                newMain +=
                    '    tile_featureColor = featureProperties; \n' +
                    '    tile_featureSt = st; \n' +
                    '}';
            } else {
                // When VTF is not supported, color blend mode MIX will look incorrect due to the feature's color not being available in the vertex shader
                newMain =
                    'varying vec2 tile_featureSt; \n' +
                    'void main() \n' +
                    '{ \n' +
                    '    tile_color(vec4(1.0)); \n' +
                    '    tile_featureSt = computeSt(' + batchIdAttributeName + '); \n' +
                    '}';
            }

            return renamedSource + '\n' + getGlslComputeSt(that) + newMain;
        };
    };

    function getDefaultShader(source, applyHighlight) {
        source = ShaderSource.replaceMain(source, 'tile_main');

        if (!applyHighlight) {
            return source +
                   'void tile_color(vec4 tile_featureColor) \n' +
                   '{ \n' +
                   '    tile_main(); \n' +
                   '} \n';
        }

        // The color blend mode is intended for the RGB channels so alpha is always just multiplied.
        // gl_FragColor is multiplied by the tile color only when tile_colorBlend is 0.0 (highlight)
        return source +
               'uniform float tile_colorBlend; \n' +
               'void tile_color(vec4 tile_featureColor) \n' +
               '{ \n' +
               '    tile_main(); \n' +
               '    gl_FragColor.a *= tile_featureColor.a; \n' +
               '    float highlight = ceil(tile_colorBlend); \n' +
               '    gl_FragColor.rgb *= mix(tile_featureColor.rgb, vec3(1.0), highlight); \n' +
               '} \n';
    }

    function replaceDiffuseTextureCalls(source, diffuseAttributeOrUniformName) {
        var functionCall = 'texture2D(' + diffuseAttributeOrUniformName;

        var fromIndex = 0;
        var startIndex = source.indexOf(functionCall, fromIndex);
        var endIndex;

        while (startIndex > -1) {
            var nestedLevel = 0;
            for (var i = startIndex; i < source.length; ++i) {
                var character = source.charAt(i);
                if (character === '(') {
                    ++nestedLevel;
                } else if (character === ')') {
                    --nestedLevel;
                    if (nestedLevel === 0) {
                        endIndex = i + 1;
                        break;
                    }
                }
            }
            var extractedFunction = source.slice(startIndex, endIndex);
            var replacedFunction = 'tile_diffuse_final(' + extractedFunction + ', tile_diffuse)';

            source = source.slice(0, startIndex) + replacedFunction + source.slice(endIndex);
            fromIndex = startIndex + replacedFunction.length;
            startIndex = source.indexOf(functionCall, fromIndex);
        }

        return source;
    }

    function modifyDiffuse(source, diffuseAttributeOrUniformName, applyHighlight) {
        // If the glTF does not specify the _3DTILESDIFFUSE semantic, return the default shader.
        // Otherwise if _3DTILESDIFFUSE is defined prefer the shader below that can switch the color mode at runtime.
        if (!defined(diffuseAttributeOrUniformName)) {
            return getDefaultShader(source, applyHighlight);
        }

        // Find the diffuse uniform. Examples matches:
        //   uniform vec3 u_diffuseColor;
        //   uniform sampler2D diffuseTexture;
        var regex = new RegExp('(uniform|attribute|in)\\s+(vec[34]|sampler2D)\\s+' + diffuseAttributeOrUniformName + ';');
        var uniformMatch = source.match(regex);

        if (!defined(uniformMatch)) {
            // Could not find uniform declaration of type vec3, vec4, or sampler2D
            return getDefaultShader(source, applyHighlight);
        }

        var declaration = uniformMatch[0];
        var type = uniformMatch[2];

        source = ShaderSource.replaceMain(source, 'tile_main');
        source = source.replace(declaration, ''); // Remove uniform declaration for now so the replace below doesn't affect it

        // If the tile color is white, use the source color. This implies the feature has not been styled.
        // Highlight: tile_colorBlend is 0.0 and the source color is used
        // Replace: tile_colorBlend is 1.0 and the tile color is used
        // Mix: tile_colorBlend is between 0.0 and 1.0, causing the source color and tile color to mix
        var finalDiffuseFunction =
            'bool isWhite(vec3 color) \n' +
            '{ \n' +
            '    return all(greaterThan(color, vec3(1.0 - czm_epsilon3))); \n' +
            '} \n' +
            'vec4 tile_diffuse_final(vec4 sourceDiffuse, vec4 tileDiffuse) \n' +
            '{ \n' +
            '    vec4 blendDiffuse = mix(sourceDiffuse, tileDiffuse, tile_colorBlend); \n' +
            '    vec4 diffuse = isWhite(tileDiffuse.rgb) ? sourceDiffuse : blendDiffuse; \n' +
            '    return vec4(diffuse.rgb, sourceDiffuse.a); \n' +
            '} \n';

        // The color blend mode is intended for the RGB channels so alpha is always just multiplied.
        // gl_FragColor is multiplied by the tile color only when tile_colorBlend is 0.0 (highlight)
        var highlight =
            '    gl_FragColor.a *= tile_featureColor.a; \n' +
            '    float highlight = ceil(tile_colorBlend); \n' +
            '    gl_FragColor.rgb *= mix(tile_featureColor.rgb, vec3(1.0), highlight); \n';

        var setColor;
        if (type === 'vec3' || type === 'vec4') {
            var sourceDiffuse = (type === 'vec3') ? ('vec4(' + diffuseAttributeOrUniformName + ', 1.0)') : diffuseAttributeOrUniformName;
            var replaceDiffuse = (type === 'vec3') ? 'tile_diffuse.xyz' : 'tile_diffuse';
            regex = new RegExp(diffuseAttributeOrUniformName, 'g');
            source = source.replace(regex, replaceDiffuse);
            setColor =
                '    vec4 source = ' + sourceDiffuse + '; \n' +
                '    tile_diffuse = tile_diffuse_final(source, tile_featureColor); \n' +
                '    tile_main(); \n';
        } else if (type === 'sampler2D') {
            // Handles any number of nested parentheses
            // E.g. texture2D(u_diffuse, uv)
            // E.g. texture2D(u_diffuse, computeUV(index))
            source = replaceDiffuseTextureCalls(source, diffuseAttributeOrUniformName);
            setColor =
                '    tile_diffuse = tile_featureColor; \n' +
                '    tile_main(); \n';
        }

        source =
            'uniform float tile_colorBlend; \n' +
            'vec4 tile_diffuse = vec4(1.0); \n' +
            finalDiffuseFunction +
            declaration + '\n' +
            source + '\n' +
            'void tile_color(vec4 tile_featureColor) \n' +
            '{ \n' +
            setColor;

        if (applyHighlight) {
            source += highlight;
        }

        source += '} \n';
        return source;
    }

    Cesium3DTileBatchTable.prototype.getFragmentShaderCallback = function(handleTranslucent, diffuseAttributeOrUniformName) {
        if (this.featuresLength === 0) {
            return;
        }
        return function(source) {
            source = modifyDiffuse(source, diffuseAttributeOrUniformName, true);
            if (ContextLimits.maximumVertexTextureImageUnits > 0) {
                // When VTF is supported, per-feature show/hide already happened in the fragment shader
                source +=
                    'uniform sampler2D tile_pickTexture; \n' +
                    'varying vec2 tile_featureSt; \n' +
                    'varying vec4 tile_featureColor; \n' +
                    'void main() \n' +
                    '{ \n' +
                    '    tile_color(tile_featureColor); \n' +
                    '}';
            } else {
                if (handleTranslucent) {
                    source += 'uniform bool tile_translucentCommand; \n';
                }
                source +=
                    'uniform sampler2D tile_pickTexture; \n' +
                    'uniform sampler2D tile_batchTexture; \n' +
                    'varying vec2 tile_featureSt; \n' +
                    'void main() \n' +
                    '{ \n' +
                    '    vec4 featureProperties = texture2D(tile_batchTexture, tile_featureSt); \n' +
                    '    if (featureProperties.a == 0.0) { \n' + // show: alpha == 0 - false, non-zeo - true
                    '        discard; \n' +
                    '    } \n';

                if (handleTranslucent) {
                    source +=
                        '    bool isStyleTranslucent = (featureProperties.a != 1.0); \n' +
                        '    if (czm_pass == czm_passTranslucent) \n' +
                        '    { \n' +
                        '        if (!isStyleTranslucent && !tile_translucentCommand) \n' + // Do not render opaque features in the translucent pass
                        '        { \n' +
                        '            discard; \n' +
                        '        } \n' +
                        '    } \n' +
                        '    else \n' +
                        '    { \n' +
                        '        if (isStyleTranslucent) \n' + // Do not render translucent features in the opaque pass
                        '        { \n' +
                        '            discard; \n' +
                        '        } \n' +
                        '    } \n';
                }

                source +=
                    '    tile_color(featureProperties); \n' +
                    '} \n';
            }
            return source;
        };
    };

    Cesium3DTileBatchTable.prototype.getClassificationFragmentShaderCallback = function() {
        if (this.featuresLength === 0) {
            return;
        }
        return function(source) {
            source = ShaderSource.replaceMain(source, 'tile_main');
            if (ContextLimits.maximumVertexTextureImageUnits > 0) {
                // When VTF is supported, per-feature show/hide already happened in the fragment shader
                source +=
                    'uniform sampler2D tile_pickTexture;\n' +
                    'varying vec2 tile_featureSt; \n' +
                    'varying vec4 tile_featureColor; \n' +
                    'void main() \n' +
                    '{ \n' +
                    '    tile_main(); \n' +
                    '    gl_FragColor = tile_featureColor; \n' +
                    '}';
            } else {
                source +=
                    'uniform sampler2D tile_batchTexture; \n' +
                    'uniform sampler2D tile_pickTexture;\n' +
                    'varying vec2 tile_featureSt; \n' +
                    'void main() \n' +
                    '{ \n' +
                    '    tile_main(); \n' +
                    '    vec4 featureProperties = texture2D(tile_batchTexture, tile_featureSt); \n' +
                    '    if (featureProperties.a == 0.0) { \n' + // show: alpha == 0 - false, non-zeo - true
                    '        discard; \n' +
                    '    } \n' +
                    '    gl_FragColor = featureProperties; \n' +
                    '} \n';
            }
            return source;
        };
    };

    function getColorBlend(batchTable) {
        var tileset = batchTable._content._tileset;
        var colorBlendMode = tileset.colorBlendMode;
        var colorBlendAmount = tileset.colorBlendAmount;
        if (colorBlendMode === Cesium3DTileColorBlendMode.HIGHLIGHT) {
            return 0.0;
        }
        if (colorBlendMode === Cesium3DTileColorBlendMode.REPLACE) {
            return 1.0;
        }
        if (colorBlendMode === Cesium3DTileColorBlendMode.MIX) {
            // The value 0.0 is reserved for highlight, so clamp to just above 0.0.
            return CesiumMath.clamp(colorBlendAmount, CesiumMath.EPSILON4, 1.0);
        }
        //>>includeStart('debug', pragmas.debug);
        throw new DeveloperError('Invalid color blend mode "' + colorBlendMode + '".');
        //>>includeEnd('debug');
    }

    Cesium3DTileBatchTable.prototype.getUniformMapCallback = function() {
        if (this.featuresLength === 0) {
            return;
        }

        var that = this;
        return function(uniformMap) {
            var batchUniformMap = {
                tile_batchTexture : function() {
                    // PERFORMANCE_IDEA: we could also use a custom shader that avoids the texture read.
                    return defaultValue(that._batchTexture, that._defaultTexture);
                },
                tile_textureDimensions : function() {
                    return that._textureDimensions;
                },
                tile_textureStep : function() {
                    return that._textureStep;
                },
                tile_colorBlend : function() {
                    return getColorBlend(that);
                },
                tile_pickTexture : function() {
                    return that._pickTexture;
                }
            };

            return combine(uniformMap, batchUniformMap);
        };
    };

    Cesium3DTileBatchTable.prototype.getPickId = function() {
        return 'texture2D(tile_pickTexture, tile_featureSt)';
    };

    ///////////////////////////////////////////////////////////////////////////

    var StyleCommandsNeeded = {
        ALL_OPAQUE : 0,
        ALL_TRANSLUCENT : 1,
        OPAQUE_AND_TRANSLUCENT : 2
    };

    Cesium3DTileBatchTable.prototype.addDerivedCommands = function(frameState, commandStart, finalResolution) {
        var commandList = frameState.commandList;
        var commandEnd = commandList.length;
        var tile = this._content._tile;
        var tileset = tile._tileset;
        var bivariateVisibilityTest = tileset._skipLevelOfDetail && tileset._hasMixedContent && frameState.context.stencilBuffer;
        var styleCommandsNeeded = getStyleCommandsNeeded(this);

        for (var i = commandStart; i < commandEnd; ++i) {
            var command = commandList[i];
            var derivedCommands = command.derivedCommands.tileset;
            // Command may be marked dirty from Model shader recompilation for clipping planes
            if (!defined(derivedCommands) || command.dirty) {
                derivedCommands = {};
                command.derivedCommands.tileset = derivedCommands;
                derivedCommands.originalCommand = deriveCommand(command);
                command.dirty = false;
            }

            updateDerivedCommand(derivedCommands.originalCommand, command);

            if (styleCommandsNeeded !== StyleCommandsNeeded.ALL_OPAQUE) {
                if (!defined(derivedCommands.translucent)) {
                    derivedCommands.translucent = deriveTranslucentCommand(derivedCommands.originalCommand);
                }
                updateDerivedCommand(derivedCommands.translucent, command);
            }

            if (bivariateVisibilityTest) {
                if (command.pass !== Pass.TRANSLUCENT && !finalResolution) {
                    if (!defined(derivedCommands.zback)) {
                        derivedCommands.zback = deriveZBackfaceCommand(frameState.context, derivedCommands.originalCommand);
                    }
                    tileset._backfaceCommands.push(derivedCommands.zback);
                }
                if (!defined(derivedCommands.stencil) || tile._selectionDepth !== tile._lastSelectionDepth) {
                    derivedCommands.stencil = deriveStencilCommand(derivedCommands.originalCommand, tile._selectionDepth);
                    tile._lastSelectionDepth = tile._selectionDepth;
                }
                updateDerivedCommand(derivedCommands.stencil, command);
            }

            var opaqueCommand = bivariateVisibilityTest ? derivedCommands.stencil : derivedCommands.originalCommand;
            var translucentCommand = derivedCommands.translucent;

            // If the command was originally opaque:
            //    * If the styling applied to the tile is all opaque, use the original command
            //      (with one additional uniform needed for the shader).
            //    * If the styling is all translucent, use new (cached) derived commands (front
            //      and back faces) with a translucent render state.
            //    * If the styling causes both opaque and translucent features in this tile,
            //      then use both sets of commands.
            if (command.pass !== Pass.TRANSLUCENT) {
                if (styleCommandsNeeded === StyleCommandsNeeded.ALL_OPAQUE) {
                    commandList[i] = opaqueCommand;
                }
                if (styleCommandsNeeded === StyleCommandsNeeded.ALL_TRANSLUCENT) {
                    commandList[i] = translucentCommand;
                }
                if (styleCommandsNeeded === StyleCommandsNeeded.OPAQUE_AND_TRANSLUCENT) {
                    // PERFORMANCE_IDEA: if the tile has multiple commands, we do not know what features are in what
                    // commands so this case may be overkill.
                    commandList[i] = opaqueCommand;
                    commandList.push(translucentCommand);
                }
            } else {
                // Command was originally translucent so no need to derive new commands;
                // as of now, a style can't change an originally translucent feature to
                // opaque since the style's alpha is modulated, not a replacement.  When
                // this changes, we need to derive new opaque commands here.
                commandList[i] = opaqueCommand;
            }
        }
    };

    function updateDerivedCommand(derivedCommand, command) {
        derivedCommand.castShadows = command.castShadows;
        derivedCommand.receiveShadows = command.receiveShadows;
        derivedCommand.primitiveType = command.primitiveType;
    }

    function getStyleCommandsNeeded(batchTable) {
        var translucentFeaturesLength = batchTable._translucentFeaturesLength;

        if (translucentFeaturesLength === 0) {
            return StyleCommandsNeeded.ALL_OPAQUE;
        } else if (translucentFeaturesLength === batchTable.featuresLength) {
            return StyleCommandsNeeded.ALL_TRANSLUCENT;
        }

        return StyleCommandsNeeded.OPAQUE_AND_TRANSLUCENT;
    }

    function deriveCommand(command) {
        var derivedCommand = DrawCommand.shallowClone(command);

        // Add a uniform to indicate if the original command was translucent so
        // the shader knows not to cull vertices that were originally transparent
        // even though their style is opaque.
        var translucentCommand = (derivedCommand.pass === Pass.TRANSLUCENT);

        derivedCommand.uniformMap = defined(derivedCommand.uniformMap) ? derivedCommand.uniformMap : {};
        derivedCommand.uniformMap.tile_translucentCommand = function() {
            return translucentCommand;
        };

        return derivedCommand;
    }

    function deriveTranslucentCommand(command) {
        var derivedCommand = DrawCommand.shallowClone(command);
        derivedCommand.pass = Pass.TRANSLUCENT;
        derivedCommand.renderState = getTranslucentRenderState(command.renderState);
        return derivedCommand;
    }

    function getDisableLogDepthFragmentShaderProgram(context, shaderProgram) {
        var shader = context.shaderCache.getDerivedShaderProgram(shaderProgram, 'zBackfaceLogDepth');
        if (!defined(shader)) {
            var fs = shaderProgram.fragmentShaderSource.clone();
            fs.defines = defined(fs.defines) ? fs.defines.slice(0) : [];
            fs.defines.push('DISABLE_LOG_DEPTH_FRAGMENT_WRITE');

            shader = context.shaderCache.createDerivedShaderProgram(shaderProgram, 'zBackfaceLogDepth', {
                vertexShaderSource : shaderProgram.vertexShaderSource,
                fragmentShaderSource : fs,
                attributeLocations : shaderProgram._attributeLocations
            });
        }

        return shader;
    }

    function deriveZBackfaceCommand(context, command) {
        // Write just backface depth of unresolved tiles so resolved stenciled tiles do not appear in front
        var derivedCommand = DrawCommand.shallowClone(command);
        var rs = clone(derivedCommand.renderState, true);
        rs.cull.enabled = true;
        rs.cull.face = CullFace.FRONT;
        // Back faces do not need to write color.
        rs.colorMask = {
            red : false,
            green : false,
            blue : false,
            alpha : false
        };
        // Push back face depth away from the camera so it is less likely that back faces and front faces of the same tile
        // intersect and overlap. This helps avoid flickering for very thin double-sided walls.
        rs.polygonOffset = {
            enabled : true,
            factor : 5.0,
            units : 5.0
        };
        derivedCommand.renderState = RenderState.fromCache(rs);
        derivedCommand.castShadows = false;
        derivedCommand.receiveShadows = false;
        // Disable the depth writes in the fragment shader. The back face commands were causing the higher resolution
        // tiles to disappear.
        derivedCommand.shaderProgram = getDisableLogDepthFragmentShaderProgram(context, command.shaderProgram);
        return derivedCommand;
    }

    function deriveStencilCommand(command, reference) {
        var derivedCommand = command;
        if (command.renderState.depthMask) { // ignore if tile does not write depth (ex. translucent)
            // Tiles only draw if their selection depth is >= the tile drawn already. They write their
            // selection depth to the stencil buffer to prevent ancestor tiles from drawing on top
            derivedCommand = DrawCommand.shallowClone(command);
            var rs = clone(derivedCommand.renderState, true);
            // Stencil test is masked to the most significant 4 bits so the reference is shifted.
            // This is to prevent clearing the stencil before classification which needs the least significant
            // bits for increment/decrement operations.
            rs.stencilTest.enabled = true;
            rs.stencilTest.mask = 0xF0;
            rs.stencilTest.reference = reference << 4;
            rs.stencilTest.frontFunction = StencilFunction.GREATER_OR_EQUAL;
            rs.stencilTest.frontOperation.zPass = StencilOperation.REPLACE;
            derivedCommand.renderState = RenderState.fromCache(rs);
        }
        return derivedCommand;
    }

    function getTranslucentRenderState(renderState) {
        var rs = clone(renderState, true);
        rs.cull.enabled = false;
        rs.depthTest.enabled = true;
        rs.depthMask = false;
        rs.blending = BlendingState.ALPHA_BLEND;

        return RenderState.fromCache(rs);
    }

    ///////////////////////////////////////////////////////////////////////////

    function createTexture(batchTable, context, bytes) {
        var dimensions = batchTable._textureDimensions;
        return new Texture({
            context : context,
            pixelFormat : PixelFormat.RGBA,
            pixelDatatype : PixelDatatype.UNSIGNED_BYTE,
            source : {
                width : dimensions.x,
                height : dimensions.y,
                arrayBufferView : bytes
            },
            flipY : false,
            sampler : new Sampler({
                minificationFilter : TextureMinificationFilter.NEAREST,
                magnificationFilter : TextureMagnificationFilter.NEAREST
            })
        });
    }

    function createPickTexture(batchTable, context) {
        var featuresLength = batchTable.featuresLength;
        if (!defined(batchTable._pickTexture) && (featuresLength > 0)) {
            var pickIds = batchTable._pickIds;
            var byteLength = getByteLength(batchTable);
            var bytes = new Uint8Array(byteLength);
            var content = batchTable._content;

            // PERFORMANCE_IDEA: we could skip the pick texture completely by allocating
            // a continuous range of pickIds and then converting the base pickId + batchId
            // to RGBA in the shader.  The only consider is precision issues, which might
            // not be an issue in WebGL 2.
            for (var i = 0; i < featuresLength; ++i) {
                var pickId = context.createPickId(content.getFeature(i));
                pickIds.push(pickId);

                var pickColor = pickId.color;
                var offset = i * 4;
                bytes[offset] = Color.floatToByte(pickColor.red);
                bytes[offset + 1] = Color.floatToByte(pickColor.green);
                bytes[offset + 2] = Color.floatToByte(pickColor.blue);
                bytes[offset + 3] = Color.floatToByte(pickColor.alpha);
            }

            batchTable._pickTexture = createTexture(batchTable, context, bytes);
            content._tileset._statistics.batchTableByteLength += batchTable._pickTexture.sizeInBytes;
        }
    }

    function updateBatchTexture(batchTable) {
        var dimensions = batchTable._textureDimensions;
        // PERFORMANCE_IDEA: Instead of rewriting the entire texture, use fine-grained
        // texture updates when less than, for example, 10%, of the values changed.  Or
        // even just optimize the common case when one feature show/color changed.
        batchTable._batchTexture.copyFrom({
            width : dimensions.x,
            height : dimensions.y,
            arrayBufferView : batchTable._batchValues
        });
    }

    Cesium3DTileBatchTable.prototype.update = function(tileset, frameState) {
        var context = frameState.context;
        this._defaultTexture = context.defaultTexture;

        var passes = frameState.passes;
        if (passes.pick || passes.postProcess) {
            createPickTexture(this, context);
        }

        if (this._batchValuesDirty) {
            this._batchValuesDirty = false;

            // Create batch texture on-demand
            if (!defined(this._batchTexture)) {
                this._batchTexture = createTexture(this, context, this._batchValues);
                tileset._statistics.batchTableByteLength += this._batchTexture.sizeInBytes;
            }

            updateBatchTexture(this);  // Apply per-feature show/color updates
        }
    };

    Cesium3DTileBatchTable.prototype.isDestroyed = function() {
        return false;
    };

    Cesium3DTileBatchTable.prototype.destroy = function() {
        this._batchTexture = this._batchTexture && this._batchTexture.destroy();
        this._pickTexture = this._pickTexture && this._pickTexture.destroy();

        var pickIds = this._pickIds;
        var length = pickIds.length;
        for (var i = 0; i < length; ++i) {
            pickIds[i].destroy();
        }

        return destroyObject(this);
    };

    return Cesium3DTileBatchTable;
});