diff --git a/src/MainWindow.h b/src/MainWindow.h
index 029da467..192a9b5a 100644
--- a/src/MainWindow.h
+++ b/src/MainWindow.h
@@ -51,7 +51,7 @@ public:
 	static const int maxRecentFiles = 10;
 	QAction *actionRecentFile[maxRecentFiles];
 
-	MainWindow(const char *filename = 0);
+	MainWindow(const QString &filename);
 	~MainWindow();
 
 protected:
diff --git a/src/context.cc b/src/context.cc
index 8c843745..a9ccc98e 100644
--- a/src/context.cc
+++ b/src/context.cc
@@ -28,6 +28,8 @@
 #include "function.h"
 #include "module.h"
 #include "printutils.h"
+#include <QFileInfo>
+#include <QDir>
 
 Context::Context(const Context *parent)
 {
@@ -35,6 +37,7 @@ Context::Context(const Context *parent)
 	functions_p = NULL;
 	modules_p = NULL;
 	inst_p = NULL;
+	if (parent) document_path = parent->document_path;
 	ctx_stack.append(this);
 }
 
@@ -109,3 +112,8 @@ AbstractNode *Context::evaluate_module(const ModuleInstantiation *inst) const
 	return NULL;
 }
 
+QString Context::get_absolute_path(const QString &filename) const
+{
+	return QFileInfo(QDir(this->document_path), filename).absoluteFilePath();
+}
+
diff --git a/src/context.h b/src/context.h
index e78c8833..fa679920 100644
--- a/src/context.h
+++ b/src/context.h
@@ -14,6 +14,7 @@ public:
 	const QHash<QString, class AbstractFunction*> *functions_p;
 	const QHash<QString, class AbstractModule*> *modules_p;
 	const class ModuleInstantiation *inst_p;
+	QString document_path;
 
 	static QVector<const Context*> ctx_stack;
 
@@ -25,6 +26,8 @@ public:
 	void set_variable(QString name, Value value);
 	Value lookup_variable(QString name, bool silent = false) const;
 
+	QString get_absolute_path(const QString &filename) const;
+
 	Value evaluate_function(QString name, const QVector<QString> &argnames, const QVector<Value> &argvalues) const;
 	class AbstractNode *evaluate_module(const ModuleInstantiation *inst) const;
 };
diff --git a/src/dxfdim.cc b/src/dxfdim.cc
index 4b0cb595..02a12742 100644
--- a/src/dxfdim.cc
+++ b/src/dxfdim.cc
@@ -29,6 +29,7 @@
 #include "dxfdata.h"
 #include "builtin.h"
 #include "printutils.h"
+#include "context.h"
 
 #include <math.h>
 #include <sys/types.h>
@@ -39,7 +40,7 @@
 QHash<QString,Value> dxf_dim_cache;
 QHash<QString,Value> dxf_cross_cache;
 
-Value builtin_dxf_dim(const QVector<QString> &argnames, const QVector<Value> &args)
+Value builtin_dxf_dim(const Context *ctx, const QVector<QString> &argnames, const QVector<Value> &args)
 {
 	QString filename;
 	QString layername;
@@ -50,7 +51,7 @@ Value builtin_dxf_dim(const QVector<QString> &argnames, const QVector<Value> &ar
 
 	for (int i = 0; i < argnames.count() && i < args.count(); i++) {
 		if (argnames[i] == "file")
-			filename = args[i].text;
+			filename = ctx->get_absolute_path(args[i].text);
 		if (argnames[i] == "layer")
 			layername = args[i].text;
 		if (argnames[i] == "origin")
@@ -124,7 +125,7 @@ Value builtin_dxf_dim(const QVector<QString> &argnames, const QVector<Value> &ar
 	return Value();
 }
 
-Value builtin_dxf_cross(const QVector<QString> &argnames, const QVector<Value> &args)
+Value builtin_dxf_cross(const Context *ctx, const QVector<QString> &argnames, const QVector<Value> &args)
 {
 	QString filename;
 	QString layername;
@@ -134,7 +135,7 @@ Value builtin_dxf_cross(const QVector<QString> &argnames, const QVector<Value> &
 
 	for (int i = 0; i < argnames.count() && i < args.count(); i++) {
 		if (argnames[i] == "file")
-			filename = args[i].text;
+			filename = ctx->get_absolute_path(args[i].text);
 		if (argnames[i] == "layer")
 			layername = args[i].text;
 		if (argnames[i] == "origin")
diff --git a/src/dxflinextrude.cc b/src/dxflinextrude.cc
index 39a39716..b1bb6f1d 100644
--- a/src/dxflinextrude.cc
+++ b/src/dxflinextrude.cc
@@ -91,7 +91,7 @@ AbstractNode *DxfLinearExtrudeModule::evaluate(const Context *ctx, const ModuleI
 	Value twist = c.lookup_variable("twist", true);
 	Value slices = c.lookup_variable("slices", true);
 
-	node->filename = file.text;
+	node->filename = c.get_absolute_path(file.text);
 	node->layername = layer.text;
 	node->height = height.num;
 	node->convexity = (int)convexity.num;
diff --git a/src/dxfrotextrude.cc b/src/dxfrotextrude.cc
index 170a7e33..58e6304f 100644
--- a/src/dxfrotextrude.cc
+++ b/src/dxfrotextrude.cc
@@ -84,7 +84,7 @@ AbstractNode *DxfRotateExtrudeModule::evaluate(const Context *ctx, const ModuleI
 	Value origin = c.lookup_variable("origin", true);
 	Value scale = c.lookup_variable("scale", true);
 
-	node->filename = file.text;
+	node->filename = c.get_absolute_path(file.text);
 	node->layername = layer.text;
 	node->convexity = (int)convexity.num;
 	origin.getv2(node->origin_x, node->origin_y);
diff --git a/src/func.cc b/src/func.cc
index fa301dca..ca7a8d40 100644
--- a/src/func.cc
+++ b/src/func.cc
@@ -80,9 +80,9 @@ BuiltinFunction::~BuiltinFunction()
 {
 }
 
-Value BuiltinFunction::evaluate(const Context*, const QVector<QString> &call_argnames, const QVector<Value> &call_argvalues) const
+Value BuiltinFunction::evaluate(const Context *ctx, const QVector<QString> &call_argnames, const QVector<Value> &call_argvalues) const
 {
-	return eval_func(call_argnames, call_argvalues);
+	return eval_func(ctx, call_argnames, call_argvalues);
 }
 
 QString BuiltinFunction::dump(QString indent, QString name) const
@@ -110,7 +110,7 @@ static double rad2deg(double x)
 	return x;
 }
 
-Value builtin_min(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_min(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() >= 1 && args[0].type == Value::NUMBER) {
 		double val = args[0].num;
@@ -122,7 +122,7 @@ Value builtin_min(const QVector<QString>&, const QVector<Value> &args)
 	return Value();
 }
 
-Value builtin_max(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_max(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() >= 1 && args[0].type == Value::NUMBER) {
 		double val = args[0].num;
@@ -134,98 +134,98 @@ Value builtin_max(const QVector<QString>&, const QVector<Value> &args)
 	return Value();
 }
 
-Value builtin_sin(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_sin(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() == 1 && args[0].type == Value::NUMBER)
 		return Value(sin(deg2rad(args[0].num)));
 	return Value();
 }
 
-Value builtin_cos(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_cos(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() == 1 && args[0].type == Value::NUMBER)
 		return Value(cos(deg2rad(args[0].num)));
 	return Value();
 }
 
-Value builtin_asin(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_asin(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() == 1 && args[0].type == Value::NUMBER)
 		return Value(rad2deg(asin(args[0].num)));
 	return Value();
 }
 
-Value builtin_acos(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_acos(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() == 1 && args[0].type == Value::NUMBER)
 		return Value(rad2deg(acos(args[0].num)));
 	return Value();
 }
 
-Value builtin_tan(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_tan(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() == 1 && args[0].type == Value::NUMBER)
 		return Value(tan(deg2rad(args[0].num)));
 	return Value();
 }
 
-Value builtin_atan(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_atan(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() == 1 && args[0].type == Value::NUMBER)
 		return Value(rad2deg(atan(args[0].num)));
 	return Value();
 }
 
-Value builtin_atan2(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_atan2(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() == 2 && args[0].type == Value::NUMBER && args[1].type == Value::NUMBER)
 		return Value(rad2deg(atan2(args[0].num, args[1].num)));
 	return Value();
 }
 
-Value builtin_round(const QVector<QString>&, const QVector<Value> &args)
-{
-	if (args.size() == 1 && args[0].type == Value::NUMBER)
-		return Value(round(args[0].num));
-	return Value();
-}
-
-Value builtin_ceil(const QVector<QString>&, const QVector<Value> &args)
-{
-	if (args.size() == 1 && args[0].type == Value::NUMBER)
-		return Value(ceil(args[0].num));
-	return Value();
-}
-
-Value builtin_floor(const QVector<QString>&, const QVector<Value> &args)
-{
-	if (args.size() == 1 && args[0].type == Value::NUMBER)
-		return Value(floor(args[0].num));
-	return Value();
-}
-
-Value builtin_pow(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_pow(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() == 2 && args[0].type == Value::NUMBER && args[1].type == Value::NUMBER)
 		return Value(pow(args[0].num, args[1].num));
 	return Value();
 }
 
-Value builtin_sqrt(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_round(const Context *, const QVector<QString>&, const QVector<Value> &args)
+{
+	if (args.size() == 1 && args[0].type == Value::NUMBER)
+		return Value(round(args[0].num));
+	return Value();
+}
+
+Value builtin_ceil(const Context *, const QVector<QString>&, const QVector<Value> &args)
+{
+	if (args.size() == 1 && args[0].type == Value::NUMBER)
+		return Value(ceil(args[0].num));
+	return Value();
+}
+
+Value builtin_floor(const Context *, const QVector<QString>&, const QVector<Value> &args)
+{
+	if (args.size() == 1 && args[0].type == Value::NUMBER)
+		return Value(floor(args[0].num));
+	return Value();
+}
+
+Value builtin_sqrt(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() == 1 && args[0].type == Value::NUMBER)
 		return Value(sqrt(args[0].num));
 	return Value();
 }
 
-Value builtin_exp(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_exp(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() == 1 && args[0].type == Value::NUMBER)
 		return Value(exp(args[0].num));
 	return Value();
 }
 
-Value builtin_log(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_log(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() == 2 && args[0].type == Value::NUMBER && args[1].type == Value::NUMBER)
 		return Value(log(args[1].num) / log(args[0].num));
@@ -234,14 +234,14 @@ Value builtin_log(const QVector<QString>&, const QVector<Value> &args)
 	return Value();
 }
 
-Value builtin_ln(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_ln(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	if (args.size() == 1 && args[0].type == Value::NUMBER)
 		return Value(log(args[0].num));
 	return Value();
 }
 
-Value builtin_str(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_str(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	QString str;
 	for (int i = 0; i < args.size(); i++)
@@ -254,7 +254,7 @@ Value builtin_str(const QVector<QString>&, const QVector<Value> &args)
 	return Value(str);
 }
 
-Value builtin_lookup(const QVector<QString>&, const QVector<Value> &args)
+Value builtin_lookup(const Context *, const QVector<QString>&, const QVector<Value> &args)
 {
 	double p, low_p, low_v, high_p, high_v;
 	if (args.size() < 2 || !args[0].getnum(p) || args[1].vec.size() < 2 || args[1].vec[0]->vec.size() < 2)
diff --git a/src/function.h b/src/function.h
index 31ca2d69..3bb89c2c 100644
--- a/src/function.h
+++ b/src/function.h
@@ -15,7 +15,7 @@ public:
 class BuiltinFunction : public AbstractFunction
 {
 public:
-	typedef Value (*eval_func_t)(const QVector<QString> &argnames, const QVector<Value> &args);
+	typedef Value (*eval_func_t)(const Context *ctx, const QVector<QString> &argnames, const QVector<Value> &args);
 	eval_func_t eval_func;
 
 	BuiltinFunction(eval_func_t f) : eval_func(f) { }
diff --git a/src/import.cc b/src/import.cc
index f346407a..dbc67ada 100644
--- a/src/import.cc
+++ b/src/import.cc
@@ -93,7 +93,7 @@ AbstractNode *ImportModule::evaluate(const Context *ctx, const ModuleInstantiati
 	node->fs = c.lookup_variable("$fs").num;
 	node->fa = c.lookup_variable("$fa").num;
 
-	node->filename = c.lookup_variable("file").text;
+	node->filename = c.get_absolute_path(c.lookup_variable("file").text);
 	node->layername = c.lookup_variable("layer", true).text;
 	node->convexity = c.lookup_variable("convexity", true).num;
 
diff --git a/src/mainwin.cc b/src/mainwin.cc
index 296cdb5d..0767a058 100644
--- a/src/mainwin.cc
+++ b/src/mainwin.cc
@@ -117,7 +117,7 @@ static char copyrighttext[] =
 
 QPointer<MainWindow> MainWindow::current_win = NULL;
 
-MainWindow::MainWindow(const char *filename)
+MainWindow::MainWindow(const QString &filename)
 {
 	setupUi(this);
 
@@ -299,7 +299,7 @@ MainWindow::MainWindow(const char *filename)
 	PRINT(copyrighttext);
 	PRINT("");
 
-	if (filename) {
+	if (!filename.isEmpty()) {
 		openFile(filename);
 	} else {
 		setFileName("");
@@ -387,7 +387,7 @@ static void report_func(const class AbstractNode*, void *vp, int mark)
 #ifdef ENABLE_MDI
 void MainWindow::requestOpenFile(const QString &filename)
 {
-	new MainWindow(filename.toUtf8());
+	new MainWindow(filename);
 }
 #else
 void MainWindow::requestOpenFile(const QString &)
@@ -400,7 +400,7 @@ MainWindow::openFile(const QString &new_filename)
 {
 #ifdef ENABLE_MDI
 	if (!editor->toPlainText().isEmpty()) {
-		new MainWindow(new_filename.toUtf8());
+		new MainWindow(new_filename);
 		current_win = NULL;
 		return;
 	}
@@ -415,6 +415,7 @@ MainWindow::setFileName(const QString &filename)
 {
 	if (filename.isEmpty()) {
 		this->fileName.clear();
+		this->root_ctx.document_path = currentdir;
 		setWindowTitle("OpenSCAD - New Document[*]");
 	}
 	else {
@@ -437,6 +438,7 @@ MainWindow::setFileName(const QString &filename)
 			this->fileName = fileinfo.fileName();
 		}
 		
+		this->root_ctx.document_path = fileinfo.dir().absolutePath();
 		QDir::setCurrent(fileinfo.dir().absolutePath());
 	}
 
@@ -773,7 +775,7 @@ void MainWindow::compileCSG(bool procevents)
 void MainWindow::actionNew()
 {
 #ifdef ENABLE_MDI
-	new MainWindow;
+	new MainWindow(QString());
 #else
 	setFileName("");
 	editor->setPlainText("");
diff --git a/src/openscad.cc b/src/openscad.cc
index f23848b0..71d0297e 100644
--- a/src/openscad.cc
+++ b/src/openscad.cc
@@ -59,6 +59,7 @@ static void help(const char *progname)
 QString commandline_commands;
 const char *make_command = NULL;
 QSet<QString> dependencies;
+QString currentdir;
 QString examplesdir;
 QString librarydir;
 
@@ -101,6 +102,7 @@ int main(int argc, char **argv)
 #ifdef Q_WS_MAC
 	app.installEventFilter(new EventFilter(&app));
 #endif
+	QDir original_path = QDir::current();
 
   // set up groups for QSettings
   QCoreApplication::setOrganizationName("OpenSCAD");
@@ -161,6 +163,8 @@ int main(int argc, char **argv)
 		help(argv[0]);
 #endif
 
+	currentdir = QDir::currentPath();
+
 	QDir exdir(QApplication::instance()->applicationDirPath());
 #ifdef Q_WS_MAC
 	exdir.cd("../Resources"); // Examples can be bundled
@@ -232,7 +236,6 @@ int main(int argc, char **argv)
 			root_module = parse((text+commandline_commands).toAscii().data(), fileInfo.absolutePath().toLocal8Bit(), false);
 		}
 
-		QString original_path = QDir::currentPath();
 		QDir::setCurrent(fileInfo.absolutePath());
 
 		AbstractNode::resetIndexCounter();
@@ -241,7 +244,7 @@ int main(int argc, char **argv)
 		CGAL_Nef_polyhedron *root_N;
 		root_N = new CGAL_Nef_polyhedron(root_node->render_cgal_nef_polyhedron());
 
-		QDir::setCurrent(original_path);
+		QDir::setCurrent(original_path.absolutePath());
 
 		if (deps_output_file) {
 			fp = fopen(deps_output_file, "wt");
@@ -279,6 +282,8 @@ int main(int argc, char **argv)
 		installAppleEventHandlers();
 #endif		
 
+		QString qfilename = QFileInfo(original_path, filename).absoluteFilePath();
+
 #if 0 /*** disabled by clifford wolf: adds rendering artefacts with OpenCSG ***/
 		// turn on anti-aliasing
 		QGLFormat f;
@@ -287,12 +292,12 @@ int main(int argc, char **argv)
 		QGLFormat::setDefaultFormat(f);
 #endif
 #ifdef ENABLE_MDI
-		new MainWindow(filename);
+		new MainWindow(qfilename);
 		while (optind < argc)
-			new MainWindow(argv[optind++]);
+			new MainWindow(QFileInfo(original_path, argv[optind++]).absoluteFilePath());
 		app.connect(&app, SIGNAL(lastWindowClosed()), &app, SLOT(quit()));
 #else
-		MainWindow *m = new MainWindow(filename);
+		MainWindow *m = new MainWindow(qfilename);
 		app.connect(m, SIGNAL(destroyed()), &app, SLOT(quit()));
 #endif
 		rc = app.exec();
diff --git a/src/openscad.h b/src/openscad.h
index 125cc0c0..5a1e7939 100644
--- a/src/openscad.h
+++ b/src/openscad.h
@@ -46,6 +46,10 @@ extern int parser_error_pos;
 
 extern void handle_dep(QString filename);
 
+// The CWD when application started. We shouldn't change CWD, but until we stop
+// doing this, use currentdir to get the original CWD.
+extern QString currentdir;
+
 extern QString examplesdir;
 extern QString librarydir;
 
diff --git a/src/surface.cc b/src/surface.cc
index b2abbed4..ddcd3a67 100644
--- a/src/surface.cc
+++ b/src/surface.cc
@@ -64,7 +64,7 @@ AbstractNode *SurfaceModule::evaluate(const Context *ctx, const ModuleInstantiat
 	Context c(ctx);
 	c.args(argnames, argexpr, inst->argnames, inst->argvalues);
 
-	node->filename = c.lookup_variable("file").text;
+	node->filename = c.get_absolute_path(c.lookup_variable("file").text);
 
 	Value center = c.lookup_variable("center", true);
 	if (center.type == Value::BOOL) {