diff --git a/shader/wallFace.frag b/shader/wallFace.frag
new file mode 100644
index 000000000..a4e0a29a7
--- /dev/null
+++ b/shader/wallFace.frag
@@ -0,0 +1,12 @@
+#version 430 core
+in vec2 tPos;
+in vec4 gColor;
+
+uniform sampler2D tex;
+
+out vec4 fColor;
+
+void main()
+{
+  fColor = gColor * texture(tex,tPos);
+}
diff --git a/shader/wallFace.geom b/shader/wallFace.geom
new file mode 100644
index 000000000..7f2cc9b7d
--- /dev/null
+++ b/shader/wallFace.geom
@@ -0,0 +1,36 @@
+#version 430 core
+layout (points) in;
+layout (triangle_strip, max_vertices = 4) out;
+
+in vec4 vColor [];
+out vec4 gColor;
+out vec2 tPos;
+
+uniform mat4 perpMat;
+
+// consider using isLHS to check if the wall is facing the center
+float isLHS (vec2 startV, vec2 testV)
+{
+    return sign( -startV.x * testV.y + startV.y * testV.x);
+}
+
+void main()
+{
+    gColor = vColor[0];
+
+vec4 p1 = vec4 (gl_in[0].gl_Position.xy,0,1);
+vec4 p2 = vec4 (gl_in[0].gl_Position.zw,0,1);
+vec4 p3 = vec4 (p1.xy,-0.5,1);
+vec4 p4 = vec4 (p2.xy,-0.5,1);
+
+vec4 a1 = perpMat * p1;
+vec4 a2 = perpMat * p2;
+vec4 a3 = perpMat * p3;
+vec4 a4 = perpMat * p4;
+
+  tPos = vec2 ( 1,-1) ; gl_Position = a1; EmitVertex();
+  tPos = vec2 ( 1, 1) ; gl_Position = a3; EmitVertex();
+  tPos = vec2 (-1,-1) ; gl_Position = a2; EmitVertex();
+  tPos = vec2 (-1, 1) ; gl_Position = a4; EmitVertex();
+  EndPrimitive();
+}
diff --git a/shader/wallFace.vert b/shader/wallFace.vert
new file mode 100644
index 000000000..0456509f9
--- /dev/null
+++ b/shader/wallFace.vert
@@ -0,0 +1,11 @@
+#version 430 core
+layout (location = 0) in vec4 poss;
+layout (location = 1) in vec4 color;
+
+out vec4 vColor;
+
+void main()
+{
+  gl_Position = poss;
+  vColor = color;
+}
diff --git a/shader/wallFace.vet b/shader/wallFace.vet
new file mode 100644
index 000000000..0456509f9
--- /dev/null
+++ b/shader/wallFace.vet
@@ -0,0 +1,11 @@
+#version 430 core
+layout (location = 0) in vec4 poss;
+layout (location = 1) in vec4 color;
+
+out vec4 vColor;
+
+void main()
+{
+  gl_Position = poss;
+  vColor = color;
+}
diff --git a/src/Picture/Render.hs b/src/Picture/Render.hs
index e1b8caf8b..5fd2ea0be 100644
--- a/src/Picture/Render.hs
+++ b/src/Picture/Render.hs
@@ -53,8 +53,11 @@ renderPicture' :: RenderData -> Float -> Float -> (Float,Float) -> (Float,Float)
                     (Float,Float) -> Picture -> IO (Word32,Word32)
 renderPicture' pdata rot zoom trans wins wallPoints lightPoints
                     viewFroms pic = do
+    startTicks <- SDL.ticks
     setCommonUniforms pdata rot zoom trans wins
     renderPicture pdata rot zoom trans wins wallPoints lightPoints viewFroms pic
+    endTicks <- SDL.ticks
+    return (startTicks, endTicks - startTicks)
 
 renderPicture :: RenderData -> Float -> Float -> (Float,Float) -> (Float,Float) ->
                     [(Point2,Point2)] -> [Point4] ->