3D Tiles - Ternary Functions

Source/Core/Math.js

@@ -699,7 +699,7 @@ define([
     };
 
     /**
-     * Constraint a value to lie between two values.
+     * Constrains a value to lie between two values.
      *
      * @param {Number} value The value to constrain.
      * @param {Number} min The minimum value.

Source/Scene/Expression.js

@@ -55,14 +55,19 @@ define([
     var unaryFunctions = {
         abs : Math.abs,
         sqrt : Math.sqrt,
-        cos : Math.cos,
         sin : Math.sin,
+        cos : Math.cos,
         tan : Math.tan,
         acos : Math.acos,
         asin : Math.asin,
         atan : Math.atan,
-        radians : CesiumMath.toRadians,
-        degrees : CesiumMath.toDegrees
+        degrees : CesiumMath.toDegrees,
+        radians : CesiumMath.toRadians
+    };
+
+    var ternaryFunctions = {
+        clamp : CesiumMath.clamp,
+        mix: CesiumMath.lerp
     };
 
     /**
@@ -370,6 +375,16 @@ define([
             //>>includeEnd('debug');
             val = createRuntimeAst(expression, args[0]);
             return new Node(ExpressionNodeType.UNARY, call, val);
+        } else if (defined(ternaryFunctions[call])) {
+            //>>includeStart('debug', pragmas.debug);
+            if (args.length < 3 || args.length > 3) {
+                throw new DeveloperError('Error: ' + call + ' requires exactly three arguments.');
+            }
+            //>>includeEnd('debug');
+            left = createRuntimeAst(expression, args[0]);
+            right = createRuntimeAst(expression, args[1]);
+            var test = createRuntimeAst(expression, args[2]);
+            return new Node(ExpressionNodeType.TERNARY, call, left, right, test);
         } else if (defined(binaryFunctions[call])) {
             //>>includeStart('debug', pragmas.debug);
             if (args.length < 2 || args.length > 2) {
@@ -647,6 +662,8 @@ define([
             if (node._value === 'TILES3D_TILESET_TIME') {
                 node.evaluate = evaluateTime;
             }
+        } else if (node._type === ExpressionNodeType.TERNARY) {
+            node.evaluate = getEvaluateTernaryFunction(node._value);
         } else {
             node.evaluate = node._evaluateLiteral;
         }
@@ -670,6 +687,13 @@ define([
         };
     }
 
+    function getEvaluateTernaryFunction(call) {
+        var evaluate = ternaryFunctions[call];
+        return function(feature) {
+            return evaluate(this._left.evaluate(feature), this._right.evaluate(feature));
+        };
+    }
+
     Node.prototype._evaluateLiteral = function(frameState, feature) {
         return this._value;
     };
@@ -1186,12 +1210,6 @@ define([
                     return 'float(' + left + ')';
                 } else if (defined(unaryFunctions[value])) {
                     return value + '(' + left + ')';
-                } else if (value === 'abs') {
-                    return 'abs(' + left + ')';
-                } else if (value === 'cos') {
-                    return 'cos(' + left + ')';
-                } else if (value === 'sqrt') {
-                    return 'sqrt(' + left + ')';
                 }
                 //>>includeStart('debug', pragmas.debug);
                 else if ((value === 'isNaN') || (value === 'isFinite') || (value === 'String')) {
@@ -1327,6 +1345,11 @@ define([
                 if (value === 'TILES3D_TILESET_TIME') {
                     return 'u_tilesetTime';
                 }
+                break;
+            case ExpressionNodeType.TERNARY:
+                if (defined(ternaryFunctions[value])) {
+                    return value + '(' + left + ', ' + right + ', ' + test + ')';
+                }
         }
     };
 

Source/Scene/ExpressionNodeType.js

@@ -11,21 +11,22 @@ define([
     var ExpressionNodeType = {
         VARIABLE : 0,
         UNARY : 1,
-        BINARY : 2,
-        CONDITIONAL : 3,
-        MEMBER : 4,
-        FUNCTION_CALL : 5,
-        ARRAY : 6,
-        REGEX: 7,
-        VARIABLE_IN_STRING : 8,
-        LITERAL_NULL : 9,
-        LITERAL_BOOLEAN : 10,
-        LITERAL_NUMBER : 11,
-        LITERAL_STRING : 12,
-        LITERAL_COLOR : 13,
-        LITERAL_REGEX : 14,
-        LITERAL_UNDEFINED : 15,
-        LITERAL_GLOBAL : 16
+        TERNARY : 2,
+        BINARY : 3,
+        CONDITIONAL : 4,
+        MEMBER : 5,
+        FUNCTION_CALL : 6,
+        ARRAY : 7,
+        REGEX: 8,
+        VARIABLE_IN_STRING : 9,
+        LITERAL_NULL : 10,
+        LITERAL_BOOLEAN : 11,
+        LITERAL_NUMBER : 12,
+        LITERAL_STRING : 13,
+        LITERAL_COLOR : 14,
+        LITERAL_REGEX : 15,
+        LITERAL_UNDEFINED : 16,
+        LITERAL_GLOBAL : 17
     };
 
     return freezeObject(ExpressionNodeType);

Specs/Scene/ExpressionSpec.js

@@ -988,6 +988,58 @@ defineSuite([
         }).toThrowDeveloperError();
     });
 
+    it('evaluates clamp function', function() {
+        var expression = new Expression('clamp(50.0, 0.0, 100.0)');
+        expect(expression.evaluate(frameState, undefined)).toEqual(50.0);
+
+        expression = new Expression('clamp(50.0, 0.0, 25.0)');
+        expect(expression.evaluate(frameState, undefined)).toEqual(25.0);
+
+        expression = new Expression('clamp(50.0, 75.0, 100.0)');
+        expect(expression.evaluate(frameState, undefined)).toEqual(75.0);
+    });
+
+    it('throws if clamp function takes an invalid number of arguments', function() {
+        expect(function() {
+            return new Expression('clamp()');
+        }).toThrowDeveloperError();
+
+        expect(function() {
+            return new Expression('clamp(1)');
+        }).toThrowDeveloperError();
+
+        expect(function() {
+            return new Expression('clamp(1, 2)');
+        }).toThrowDeveloperError();
+
+        expect(function() {
+            return new Expression('clamp(1, 2, 3, 4)');
+        }).toThrowDeveloperError();
+    });
+
+    it('evaluates mix function', function() {
+        var expression = new Expression('mix(0.0, 2.0, 0.5)');
+        expect(expression.evaluate(frameState, undefined)).toEqual(1.0);
+    });
+
+    it('throws if mix function takes an invalid number of arguments', function() {
+        expect(function() {
+            return new Expression('mix()');
+        }).toThrowDeveloperError();
+
+        expect(function() {
+            return new Expression('mix(1)');
+        }).toThrowDeveloperError();
+
+        expect(function() {
+            return new Expression('mix(1, 2)');
+        }).toThrowDeveloperError();
+
+        expect(function() {
+            return new Expression('mix(1, 2, 3, 4)');
+        }).toThrowDeveloperError();
+    });
+
     it('evaluates atan2 function', function() {
         var expression = new Expression('atan2(0,1)');
         expect(expression.evaluate(frameState, undefined)).toEqualEpsilon(0.0, CesiumMath.EPSILON10);
@@ -1879,6 +1931,20 @@ defineSuite([
         expect(shaderExpression).toEqual(expected);
     });
 
+    it('gets shader expression for clamp', function() {
+        var expression = new Expression('clamp(50.0, 0.0, 100.0)');
+        var shaderExpression = expression.getShaderExpression('', {});
+        var expected = 'clamp(50.0, 0.0, 100.0)';
+        expect(shaderExpression).toEqual(expected);
+    });
+
+    it('gets shader expression for mix', function() {
+        var expression = new Expression('mix(0.0, 2.0, 0.5)');
+        var shaderExpression = expression.getShaderExpression('', {});
+        var expected = 'mix(0.0, 2.0, 0.5)';
+        expect(shaderExpression).toEqual(expected);
+    });
+
     it('gets shader expression for atan2', function() {
         var expression = new Expression('atan2(0.0,1.0)');
         var shaderExpression = expression.getShaderExpression('', {});