diff --git a/parser/nodes.cc b/parser/nodes.cc
index 2584bb9..f4331e4 100644
--- a/parser/nodes.cc
+++ b/parser/nodes.cc
@@ -1,14 +1,53 @@
 
 #include <stdlib.h>
+#include <math.h>
 
 #include <vector>
 #include <iostream>
 #include <typeinfo>
+#include <map>
 
 #include "nodes.h"
 
 using namespace std;
 
+typedef NodeRef (*Function)(NodeRef args);
+
+NodeRef CosFunction(NodeRef args);
+NodeRef SinFunction(NodeRef args);
+NodeRef SqrtFunction(NodeRef args);
+NodeRef AbsFunction(NodeRef args);
+
+static const struct {
+    const char * fn_name;
+    Function fn;
+} functions[] = {
+    {"cos", CosFunction},
+    {"sin", SinFunction},
+    {"sqrt", SqrtFunction},
+    {"abs", AbsFunction}
+};
+
+class FunctionMap : public map<string, Function>
+{
+    public:
+        FunctionMap()
+        {
+            for (unsigned int i = 0;
+                 i < sizeof(functions)/sizeof(functions[0]);
+                 i++)
+            {
+                (*this)[functions[i].fn_name] = functions[i].fn;
+            }
+        }
+        bool contains(const string & key)
+        {
+            return find(key) != end();
+        }
+};
+
+static FunctionMap function_map;
+
 void Node::evaluateChildren(refptr<Node> parent)
 {
     /* recursively evaluate all children nodes */
@@ -169,3 +208,59 @@ NodeRef ElseNode::evaluate()
     evaluateChildren(eval);
     return eval;
 }
+
+NodeRef FunctionCallNode::evaluate()
+{
+    if (function_map.contains(m_name->getString()))
+    {
+        return function_map[m_name->getString()](m_parameters);
+    }
+    cerr << "Error: no function \"" << m_name->getString() << "\" defined!"
+        << endl;
+    exit(4);
+}
+
+
+/**************************************************************************
+ * Scene file functions                                                   *
+ *************************************************************************/
+NodeRef CosFunction(NodeRef args)
+{
+    if (args->getChildren().size() != 1)
+    {
+        cerr << "Error: cos function requires 1 argument" << endl;
+        exit(4);
+    }
+    return new NumberNode(cos(args->getChildren()[0]->evaluate()->getNumber()));
+}
+
+NodeRef SinFunction(NodeRef args)
+{
+    if (args->getChildren().size() != 1)
+    {
+        cerr << "Error: sin function requires 1 argument" << endl;
+        exit(4);
+    }
+    return new NumberNode(sin(args->getChildren()[0]->evaluate()->getNumber()));
+}
+
+NodeRef SqrtFunction(NodeRef args)
+{
+    if (args->getChildren().size() != 1)
+    {
+        cerr << "Error: sqrt function requires 1 argument" << endl;
+        exit(4);
+    }
+    return new NumberNode(sqrt(args->getChildren()[0]->evaluate()->getNumber()));
+}
+
+NodeRef AbsFunction(NodeRef args)
+{
+    if (args->getChildren().size() != 1)
+    {
+        cerr << "Error: abs function requires 1 argument" << endl;
+        exit(4);
+    }
+    return new NumberNode(fabs(args->getChildren()[0]->evaluate()->getNumber()));
+}
+
diff --git a/parser/nodes.h b/parser/nodes.h
index e0c865d..d949e1d 100644
--- a/parser/nodes.h
+++ b/parser/nodes.h
@@ -750,6 +750,19 @@ class ElseNode : public Node
         virtual NodeRef evaluate();
 };
 
+class FunctionCallNode : public Node
+{
+    public:
+        FunctionCallNode(NodeRef name, NodeRef parameters)
+        {
+            m_name = name;
+            m_parameters = parameters;
+        }
+        virtual NodeRef evaluate();
+    protected:
+        NodeRef m_name, m_parameters;
+};
+
 /* this class is only used to hold a set of items coming out of a class's
  * evaluate() from above. the evaluateChildren() top-level method will
  * propagate children of this class up to the level of their parent */
diff --git a/parser/parser.yy b/parser/parser.yy
index 6385174..b4664f1 100644
--- a/parser/parser.yy
+++ b/parser/parser.yy
@@ -358,6 +358,7 @@ expression: term                    { $$ = $1; }
               $$ = new BinOpNode('-', new NumberNode(0.0), $2);
           }
           | stmt_expression         { $$ = $1; }
+          | function_call           { $$ = $1; }
           ;
 
 maybe_expression: /* empty */
@@ -439,6 +440,28 @@ if_more: /* empty */
            $$->addChildren($3);
        }
        ;
+
+function_call: IDENTIFIER LPAREN function_call_parameters RPAREN {
+                $$ = new FunctionCallNode($1, $3);
+             }
+             ;
+
+function_call_parameters: /* empty */
+                        | expression function_call_more_parameters {
+                            $$ = new ItemsNode();
+                            $$->addChild($1);
+                            $$->addChildren($2);
+                        }
+                        ;
+
+function_call_more_parameters: /* empty */
+                             | COMMA expression function_call_more_parameters {
+                                $$ = new ItemsNode();
+                                $$->addChild($2);
+                                $$->addChildren($3);
+                             }
+                             ;
+
 %%
 
 refptr<Node> parse(const char * fileName, refptr<Scope> scope)
diff --git a/scenes/if-test.fart b/scenes/if-test.fart
index 99786cc..400a4eb 100644
--- a/scenes/if-test.fart
+++ b/scenes/if-test.fart
@@ -44,7 +44,11 @@ scene
                 }
                 else
                 {
-                    material mat3
+                    material
+                    {
+                        color <1, 0, 0>
+                        transparency abs($x / 120)
+                    }
                 }
             }
             $m := $m + 1