diff --git a/code/3rd_party/3rd_QGLViewer/QGLViewer/qglviewer.cpp b/code/3rd_party/3rd_QGLViewer/QGLViewer/qglviewer.cpp
index 0e0d713..ab8343b 100644
--- a/code/3rd_party/3rd_QGLViewer/QGLViewer/qglviewer.cpp
+++ b/code/3rd_party/3rd_QGLViewer/QGLViewer/qglviewer.cpp
@@ -270,15 +270,6 @@ void QGLViewer::initializeGL() {
   setForegroundColor(QColor(180, 180, 180));
   setBackgroundColor(QColor(51, 51, 51));
 
-  // Clear the buffer where we're going to draw
-  if (format().stereo()) {
-    glDrawBuffer(GL_BACK_RIGHT);
-    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
-    glDrawBuffer(GL_BACK_LEFT);
-    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
-  } else
-    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
-
   // Calls user defined method. Default emits a signal.
   init();
 
@@ -295,6 +286,15 @@ camera in the world coordinate system. \arg draw() (or fastDraw() when the
 camera is manipulated) : main drawing method. Should be overloaded. \arg
 postDraw() : display of visual hints (world axis, FPS...) */
 void QGLViewer::paintGL() {
+      // Clear the buffer where we're going to draw
+  if (format().stereo()) {
+    glDrawBuffer(GL_BACK_RIGHT);
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+    glDrawBuffer(GL_BACK_LEFT);
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+  } else
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
   if (displaysInStereo()) {
     for (int view = 1; view >= 0; --view) {
       // Clears screen, set model view matrix with shifted matrix for ith buffer
diff --git a/code/City3D/paint_canvas.cpp b/code/City3D/paint_canvas.cpp
index 8fd9476..1ec0220 100755
--- a/code/City3D/paint_canvas.cpp
+++ b/code/City3D/paint_canvas.cpp
@@ -181,6 +181,8 @@ void PaintCanvas::init()
 
 
 void PaintCanvas::draw() {
+    ogf_check_gl;
+
 	if (point_set_ && show_point_set_ && point_set_render_)
 		point_set_render_->draw(point_set_);