3D Tiles - Ternary Functions

Source/Core/Math.js

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

Source/Scene/Expression.js

@@ -47,15 +47,20 @@ define([
 
     var unaryFunctions = {
         abs : Math.abs,
-        sqrt : Math.sqrt,
-        cos : Math.cos,
-        sin : Math.sin,
-        tan : Math.tan,
         acos : Math.acos,
         asin : Math.asin,
         atan : Math.atan,
+        cos : Math.cos,
+        degrees : CesiumMath.toDegrees,
         radians : CesiumMath.toRadians,
-        degrees : CesiumMath.toDegrees
+        sin : Math.sin,
+        sqrt : Math.sqrt,
+        tan : Math.tan
+    };
+
+    var ternaryFunctions = {
+        clamp : CesiumMath.clamp,
+        mix: CesiumMath.lerp
     };
 
     /**
@@ -383,6 +388,18 @@ define([
             return new Node(ExpressionNodeType.UNARY, call, val);
         } else if (call === 'regExp') {
             return parseRegex(expression, ast);
+        } 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');
+            val = [
+                createRuntimeAst(expression, args[0]),
+                createRuntimeAst(expression, args[1]),
+                createRuntimeAst(expression, args[2])
+            ];
+            return new Node(ExpressionNodeType.TERNARY, call, val);
         }
 
         //>>includeStart('debug', pragmas.debug);
@@ -629,6 +646,8 @@ 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;
         }
@@ -645,6 +664,13 @@ define([
         };
     }
 
+    function getEvaluateTernaryFunction(call) {
+        var evaluate = ternaryFunctions[call];
+        return function(feature) {
+            return evaluate(this._left.evaluate(feature));
+        };
+    }
+
     Node.prototype._evaluateLiteral = function(frameState, feature) {
         return this._value;
     };
@@ -1161,12 +1187,6 @@ 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')) {
@@ -1298,6 +1318,11 @@ 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

@@ -25,7 +25,8 @@ define([
         LITERAL_COLOR : 13,
         LITERAL_REGEX : 14,
         LITERAL_UNDEFINED : 15,
-        LITERAL_GLOBAL : 16
+        LITERAL_GLOBAL : 16,
+        TERNARY : 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(undefined)).toEqual(50.0);
+
+        expression = new Expression('clamp(50.0, 0.0, 25.0)');
+        expect(expression.evaluate(undefined)).toEqual(25.0);
+
+        expression = new Expression('clamp(50.0, 75.0, 100.0)');
+        expect(expression.evaluate(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(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 ternary conditional', function() {
         var expression = new Expression('true ? "first" : "second"');
         expect(expression.evaluate(frameState, undefined)).toEqual('first');
@@ -1807,6 +1859,20 @@ 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('throws when getting shader expression for regex', function() {
         var expression = new Expression('regExp("a").test("abc")');
         expect(function() {