First iteration of the urban effect with relief mapping. Relief map by HB-Gral.

Effects/urban.eff

@@ -0,0 +1,90 @@
+<?xml version="1.0" encoding="utf-8"?>
+<PropertyList>
+  <name>Effects/urban</name>
+  <inherits-from>Effects/terrain-default</inherits-from>
+  <parameters>
+    <texture n="2">
+      <image>Textures.high/Terrain/city1-relief.png</image>
+      <filter>linear-mipmap-linear</filter>
+      <wrap-s>repeat</wrap-s>
+      <wrap-t>repeat</wrap-t>
+      <internal-format>normalized</internal-format>
+    </texture>
+  </parameters>
+  <technique n="9">
+    <predicate>
+      <and>
+        <property>/sim/rendering/urban-shader</property>
+        <property>/sim/rendering/shader-effects</property>
+        <or>
+          <less-equal>
+            <value type="float">2.0</value>
+            <glversion/>
+          </less-equal>
+          <and>
+            <extension-supported>GL_ARB_shader_objects</extension-supported>
+            <extension-supported>GL_ARB_shading_language_100</extension-supported>
+            <extension-supported>GL_ARB_vertex_shader</extension-supported>
+            <extension-supported>GL_ARB_fragment_shader</extension-supported>
+          </and>
+        </or>
+      </and>
+    </predicate>
+    <pass>
+      <lighting>true</lighting>
+      <material>
+        <ambient><use>material/ambient</use></ambient>
+        <diffuse><use>material/diffuse</use></diffuse>
+        <specular><use>material/specular</use></specular>
+        <color-mode>ambient-and-diffuse</color-mode>
+      </material>
+      <blend><use>transparent</use></blend>
+      <alpha-test><use>transparent</use></alpha-test>
+      <shade-model>smooth</shade-model>
+      <cull-face>back</cull-face>
+      <render-bin>
+        <bin-number><use>render-bin/bin-number</use></bin-number>
+        <bin-name><use>render-bin/bin-name</use></bin-name>
+      </render-bin>
+      <texture-unit>
+        <unit>0</unit>
+          <image><use>texture[0]/image</use></image>
+          <filter><use>texture[0]/filter</use></filter>
+          <wrap-s><use>texture[0]/wrap-s</use></wrap-s>
+          <wrap-t><use>texture[0]/wrap-t</use></wrap-t>
+          <internal-format>
+            <use>texture[0]/internal-format</use>
+          </internal-format>
+      </texture-unit>
+      <texture-unit>
+        <unit>1</unit>
+          <image><use>texture[2]/image</use></image>
+          <filter><use>texture[2]/filter</use></filter>
+          <wrap-s><use>texture[2]/wrap-s</use></wrap-s>
+          <wrap-t><use>texture[2]/wrap-t</use></wrap-t>
+          <internal-format>
+            <use>texture[2]/internal-format</use>
+          </internal-format>
+      </texture-unit>
+      <program>
+        <vertex-shader>Shaders/urban.vert</vertex-shader>
+        <fragment-shader>Shaders/urban.frag</fragment-shader>
+      </program>
+      <uniform>
+        <name>BaseTex</name>
+        <type>sampler-2d</type>
+        <value type="int">0</value>
+      </uniform>
+      <uniform>
+        <name>NormalTex</name>
+        <type>sampler-2d</type>
+        <value type="int">1</value>
+      </uniform>
+      <uniform>
+        <name>depth_factor</name>
+        <type>float</type>
+        <value type="float">0.005</value>
+      </uniform>
+    </pass>
+  </technique>
+</PropertyList>

Shaders/urban.frag

@@ -0,0 +1,85 @@
+#version 120
+
+varying vec4  rawpos;
+varying vec4  ecPosition;
+varying vec3  VNormal;
+varying vec3  VTangent;
+varying vec3  VBinormal;
+varying vec3  Normal;
+varying vec4  constantColor;
+
+uniform sampler2D BaseTex;
+uniform sampler2D NormalTex;
+uniform float depth_factor;
+
+const float scale = 1.0;
+
+float ray_intersect(sampler2D reliefMap, vec2 dp, vec2 ds)
+{
+	const int linear_search_steps = 10;
+
+	float size = 1.0 / float(linear_search_steps);
+	float depth = 0.0;
+	float best_depth = 1.0;
+
+	for(int i = 0; i < linear_search_steps - 1; ++i)
+	{
+		depth += size;
+		float t = texture2D(reliefMap, dp + ds * depth).a;
+		if(best_depth > 0.996)
+			if(depth >= t)
+				best_depth = depth;
+	}
+	depth = best_depth;
+
+	const int binary_search_steps = 5;
+
+	for(int i = 0; i < binary_search_steps; ++i)
+	{
+		size *= 0.5;
+		float t = texture2D(reliefMap, dp + ds * depth).a;
+		if(depth >= t)
+		{
+			best_depth = depth;
+			depth -= 2.0 * size;
+		}
+		depth += size;
+	}
+
+	return(best_depth);
+}
+
+void main (void)
+{
+	vec3 V = normalize(ecPosition.xyz);
+	vec3 s = vec3(dot(V, VTangent), dot(V, VBinormal), dot(VNormal, V));
+	vec2 ds = s.xy * depth_factor / s.z;
+	vec2 dp = gl_TexCoord[0].st;
+	float d = ray_intersect(NormalTex, dp, ds);
+
+	vec2 uv = dp + ds * d;
+	vec3 N = texture2D(NormalTex, uv).xyz * 2.0 - 1.0;
+
+	float fogFactor;
+	float fogCoord = ecPosition.z;
+	const float LOG2 = 1.442695;
+	fogFactor = exp2(-gl_Fog.density * gl_Fog.density * fogCoord * fogCoord * LOG2);
+	fogFactor = clamp(fogFactor, 0.0, 1.0);
+
+	vec4 c1 = texture2D(BaseTex, uv);
+
+	N = normalize(N.x * VTangent + N.y * VBinormal + N.z * VNormal);
+
+	vec3 l = gl_LightSource[0].position.xyz;
+	vec3 diffuse = gl_Color.rgb * max(0.0, dot(N, l));
+
+	vec4 ambient_light = constantColor + gl_LightSource[0].diffuse * vec4(diffuse, 1.0);
+
+	c1 *= ambient_light;
+	vec4 finalColor = c1;
+
+	if(gl_Fog.density == 1.0)
+		fogFactor=1.0;
+
+	gl_FragColor = mix(gl_Fog.color ,finalColor, fogFactor);
+}

Shaders/urban.vert

@@ -0,0 +1,26 @@
+varying vec4  rawpos;
+varying vec4  ecPosition;
+varying vec3  VNormal;
+varying vec3  Normal;
+varying vec3  VTangent;
+varying vec3  VBinormal;
+varying vec4  constantColor;
+
+void main(void)
+{
+    rawpos     = gl_Vertex;
+    ecPosition = gl_ModelViewMatrix * gl_Vertex;
+    VNormal = normalize(gl_NormalMatrix * gl_Normal);
+    Normal = normalize(gl_Normal);
+
+    vec3 t = normalize(cross(gl_Normal, vec3(1.0,0.0,0.0)));
+    VTangent = gl_NormalMatrix * t;
+    vec3 b = normalize(cross(gl_Normal,t));
+    VBinormal = gl_NormalMatrix * b;
+
+    gl_FrontColor = gl_Color;
+    constantColor = gl_FrontMaterial.emission
+            + gl_Color * (gl_LightModel.ambient + gl_LightSource[0].ambient);  
+    gl_Position = ftransform();
+    gl_TexCoord[0] = gl_TextureMatrix[0] * gl_MultiTexCoord0;
+}

gui/dialogs/rendering.xml

@@ -261,6 +261,15 @@
             <command>dialog-apply</command>
           </binding>
         </checkbox>
+
+        <checkbox>
+          <halign>left</halign>
+          <label>Urban effects</label>
+          <property>/sim/rendering/urban-shader</property>
+          <binding>
+            <command>dialog-apply</command>
+          </binding>
+        </checkbox>
       </group>
     </group>
   </group>

materials.xml

@@ -871,9 +871,12 @@ Shared parameters for various materials.
  </condition>
  <name>BuiltUpCover</name>
  <name>Urban</name>
+ <effect>Effects/urban</effect>
  <texture>Terrain/city1.png</texture>
+<!-- 
  <texture>Terrain/city2.png</texture>
  <texture>Terrain/city3.png</texture>
+-->
  <xsize>1024</xsize>
  <ysize>1024</ysize>
  <light-coverage>100000.0</light-coverage>

preferences.xml

@@ -136,6 +136,7 @@ Started September 2000 by David Megginson, david@megginson.com
    <crop-shader userarchive="y">0</crop-shader>
    <landmass-shader userarchive="y">0</landmass-shader>
    <water-shader userarchive="y">0</water-shader>
+   <urban-shader userarchive="y">0</urban-shader>
   </rendering>
   <model-hz type="int">120</model-hz>
   <navdb>