diff --git a/Shaders/Wireframe/createEdgeQuad.glsl b/Shaders/Wireframe/createEdgeQuad.glsl
index ea5d47a3cbebdbab35e7c3f67bb881cea7c30ef8..c4b34093306eb4134586f558613c5f23de357336 100644
--- a/Shaders/Wireframe/createEdgeQuad.glsl
+++ b/Shaders/Wireframe/createEdgeQuad.glsl
@@ -2,6 +2,31 @@
 // declare IO mapping prototype
 void sg_MapIO(const int);
 
+void computeEdgeQuadPos(const int v0, const int v1, in vec2 screenSize, in float lineWidth, 
+                        out vec4 pos0, out vec4 pos1, out vec4 pos2, out vec4 pos3)
+{
+  vec4 p0 = gl_in[v0].gl_Position;
+  vec4 p1 = gl_in[v1].gl_Position;
+  
+  // convert to screen space
+  p0.xy = p0.xy / p0.w * screenSize;
+  p1.xy = p1.xy / p1.w * screenSize;
+  
+  
+  // compute dir and normal
+  vec2 lineDir = p1.xy - p0.xy;
+  vec2 lineNormal = normalize(vec2(-lineDir.y, lineDir.x));
+  
+  
+  // create screen-aligned quad
+  vec2 offset = lineNormal * lineWidth;
+
+  pos0 = vec4( (p0.xy + offset) * p0.w / screenSize, p0.z, p0.w);
+  pos1 = vec4( (p0.xy - offset) * p0.w / screenSize, p0.z, p0.w);
+  pos2 = vec4( (p1.xy + offset) * p1.w / screenSize, p1.z, p1.w);
+  pos3 = vec4( (p1.xy - offset) * p1.w / screenSize, p1.z, p1.w);
+}
+
 // emit a screen aligned quad along the edge v1-v2
 void createEdgeQuad(const int v0, const int v1, in vec2 screenSize, in float lineWidth)
 {
diff --git a/widgets/glWidget/QtBaseViewer.cc b/widgets/glWidget/QtBaseViewer.cc
index 7d80f732ec419bc3403cbca7fd46812673202f63..62b4971c10fc627a788c66a027b37c3fb6fed804 100644
--- a/widgets/glWidget/QtBaseViewer.cc
+++ b/widgets/glWidget/QtBaseViewer.cc
@@ -63,6 +63,7 @@
 #include <ACG/GL/gl.hh>
 #include <ACG/GL/GLError.hh>
 #include <ACG/GL/FBO.hh>
+#include <ACG/GL/IRenderer.hh>
 
 #include <iostream>
 #include <string>
@@ -639,7 +640,15 @@ void glViewer::drawScene()
   if ( renderManager().activeId( properties_.viewerId() ) == 0 ) {
     drawScene_mono();
   } else {
-    renderManager().active( properties_.viewerId() )->plugin->render(glstate_,properties_);
+    RenderInterface* renderPlugin = renderManager().active( properties_.viewerId() )->plugin;
+
+    // eventually set viewer id in IRenderer
+    ACG::IRenderer* shaderRenderPlugin = dynamic_cast<ACG::IRenderer*>(renderPlugin);
+
+    if (shaderRenderPlugin)
+      shaderRenderPlugin->setViewerID( properties_.viewerId() );
+
+    renderPlugin->render(glstate_,properties_);
   }
   checkGLError();