diff --git a/Effects/urban.eff b/Effects/urban.eff
index 611178d41..4bc2932f2 100644
--- a/Effects/urban.eff
+++ b/Effects/urban.eff
@@ -29,7 +29,7 @@
 			<use>/environment/terminator-relative-position-m</use>
 		</terminator>
 		<fogtype>
-			<use>/sim/rendering/shaders/skydome</use>
+			<use>/sim/rendering/scattering-shader</use>
 		</fogtype>
 		<!-- 	END fog include -->
 
@@ -60,8 +60,9 @@
 					</and>
 				</or>
 				<or>
-					<extension-supported>GL_ATI_shader_texture_lod</extension-supported>
-					<extension-supported>GL_ARB_shader_texture_lod</extension-supported>
+					<extension-supported>GL_ATI_shader_texture_lod</extension-supported> <!-- not available in NVidia driver -->
+					<extension-supported>GL_ARB_shader_texture_lod</extension-supported> <!-- not available in NVidia driver -->
+					<extension-supported>GL_EXT_gpu_shader4</extension-supported>
 				</or>
 			</and>
 		</predicate>
@@ -288,7 +289,7 @@
 			<and>
 				<property>/sim/rendering/shaders/urban</property>
 				<less-equal>
-					<value type="float">2.0</value>
+					<value type="float">1.0</value>
 					<float-property>/sim/rendering/shaders/urban</float-property>
 				</less-equal>
 				<or>
diff --git a/Shaders/urban.frag b/Shaders/urban.frag
index b82d4a19a..a63e52116 100644
--- a/Shaders/urban.frag
+++ b/Shaders/urban.frag
@@ -28,8 +28,8 @@ uniform sampler2D NormalTex;
 uniform sampler2D QDMTex;
 uniform float depth_factor;
 uniform float tile_size;
-uniform float quality_level; // From /sim/rendering/quality-level
-uniform float snowlevel; // From /sim/rendering/snow-level-m
+uniform float quality_level;
+uniform float snowlevel;
 uniform vec3 night_color;
 
 const float scale = 1.0;
@@ -172,7 +172,7 @@ float ray_intersect(vec2 dp, vec2 ds)
 
 void main (void)
 {
-    if ( quality_level >= 3.5 ) {
+    if ( quality_level >= 3.0 ) {
         linear_search_steps = 20;
     }
     vec3 ecPos3 = ecPosition.xyz / ecPosition.w;
@@ -196,7 +196,7 @@ void main (void)
     float shadow_factor = 1.0;
 
     // Shadow
-    if ( quality_level >= 3.0 ) {
+    if ( quality_level >= 2.0 ) {
         dp += ds * d;
         vec3 sl = normalize( vec3( dot( l, VTangent ), dot( l, VBinormal ), dot( -l, VNormal ) ) );
         ds = sl.xy * depth_factor / sl.z;