Rembrandt: Create an effect for the fog stage. Duplicates the C++ code for now.

Effects/fog.eff

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+<?xml version="1.0" encoding="utf-8"?>
+<PropertyList>
+	<name>Effects/sunlight</name>
+	<technique n="11">
+		<pass>
+			<lighting>false</lighting>
+			<depth>
+				<enabled>false</enabled>
+			</depth>
+			<blend>
+				<source>src-alpha</source>
+				<destination>one-minus-src-alpha</destination>
+			</blend>
+			<render-bin>
+				<bin-number>10000</bin-number>
+				<bin-name>RenderBin</bin-name>
+			</render-bin>
+			<texture-unit>
+				<unit>0</unit>
+				<type>depth-buffer</type>
+			</texture-unit>
+			<texture-unit>
+				<unit>1</unit>
+				<type>normal-buffer</type>
+			</texture-unit>
+			<texture-unit>
+				<unit>2</unit>
+				<type>diffuse-buffer</type>
+			</texture-unit>
+			<texture-unit>
+				<unit>3</unit>
+				<type>spec-emis-buffer</type>
+			</texture-unit>
+			<program>
+				<vertex-shader>Shaders/fog.vert</vertex-shader>
+				<fragment-shader>Shaders/fog.frag</fragment-shader>
+			</program>
+			<uniform>
+				<name>depth_tex</name>
+				<type>sampler-2d</type>
+				<value type="int">0</value>
+			</uniform>
+			<uniform>
+				<name>normal_tex</name>
+				<type>sampler-2d</type>
+				<value type="int">1</value>
+			</uniform>
+			<uniform>
+				<name>color_tex</name>
+				<type>sampler-2d</type>
+				<value type="int">2</value>
+			</uniform>
+			<uniform>
+				<name>spec_emis_tex</name>
+				<type>sampler-2d</type>
+				<value type="int">3</value>
+			</uniform>
+			<!-- The following uniforms are automatically defined and initialized :
+				- fg_SunAmbientColor
+				- fg_SunDiffuseColor
+				- fg_SunSpecularColor
+				- fg_SunDirection
+				- fg_ProjectionMatrixInverse
+				- fg_ViewMatrixInverse
+				- fg_ViewMatrix
+				- fg_Planes
+				- fg_FogColor
+				- fg_FogDensity
+			-->
+		</pass>
+	</technique>
+</PropertyList>
+

Shaders/fog.frag

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+uniform sampler2D depth_tex;
+uniform sampler2D normal_tex;
+uniform sampler2D color_tex;
+uniform sampler2D spec_emis_tex;
+uniform vec4 fg_FogColor;
+uniform float fg_FogDensity;
+uniform vec3 fg_Planes;
+varying vec3 ray;
+void main() {
+    vec2 coords = gl_TexCoord[0].xy;
+    float initialized = texture2D( spec_emis_tex, coords ).a;
+    if ( initialized < 0.1 )
+        discard;
+    vec3 normal;
+    normal.xy = texture2D( normal_tex, coords ).rg * 2.0 - vec2(1.0,1.0);
+    normal.z = sqrt( 1.0 - dot( normal.xy, normal.xy ) );
+    float len = length(normal);
+    normal /= len;
+    vec3 viewDir = normalize(ray);
+    float depth = texture2D( depth_tex, coords ).r;
+    vec3 pos;
+    pos.z = - fg_Planes.y / (fg_Planes.x + depth * fg_Planes.z);
+    pos.xy = viewDir.xy / viewDir.z * pos.z;
+
+    float fogFactor = 0.0;
+    const float LOG2 = 1.442695;
+    fogFactor = exp2(-fg_FogDensity * fg_FogDensity * pos.z * pos.z * LOG2);
+    fogFactor = clamp(fogFactor, 0.0, 1.0);
+
+    gl_FragColor = vec4(fg_FogColor.rgb, 1.0 - fogFactor);
+}

Shaders/fog.vert

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+uniform mat4 fg_ProjectionMatrixInverse;
+varying vec3 ray;
+void main() {
+    gl_Position = gl_Vertex;
+    gl_TexCoord[0] = gl_MultiTexCoord0;
+    ray = (fg_ProjectionMatrixInverse * gl_Vertex).xyz;
+}