diff --git a/extern/glow-extras b/extern/glow-extras
index b97eece2d72d68f6de7a41a6b9716e9ec5564898..bd0f9d69c2d39513f4dc990d0cfaa9512259a68b 160000
--- a/extern/glow-extras
+++ b/extern/glow-extras
@@ -1 +1 @@
-Subproject commit b97eece2d72d68f6de7a41a6b9716e9ec5564898
+Subproject commit bd0f9d69c2d39513f4dc990d0cfaa9512259a68b
diff --git a/samples/wip/viewer/main.cc b/samples/wip/viewer/main.cc
index c289fc18485db1cbd21dac4a2f9b0863d1712dc6..3bc04b41238c0ecdcfdf3fea0dba4c979a455951 100644
--- a/samples/wip/viewer/main.cc
+++ b/samples/wip/viewer/main.cc
@@ -45,6 +45,10 @@ int main()
     auto edge_lengths = m.edges().map([&](pm::edge_handle e) { return edge_length(e, pos); });
     auto ptsize = m.vertices().map([&](pm::vertex_handle v) { return v.edges().avg(edge_lengths); });
 
+    // DBG
+    {
+    }
+
     // Simplest view
     glow::viewer::view(pos);
 
@@ -119,6 +123,10 @@ int main()
             v.view(pos, scaling(tg::size3(0.5f, 1, 1.5f)), glow::colors::color(0, 1, 0));
         }
 
+        // transparencies
+        view(pos, tg::color4(0, 0.4f, 0.3f, 0.2f), "transparency with fresnel");
+        view(pos, tg::color4(0, 0.4f, 0.3f, 0.2f), glow::viewer::no_fresnel, "transparency without fresnel");
+
         // Complex material
         // TODO