light two-sided polygons

Also, remove model-default.frag; for the moment one fragment shader works for
both terrain and models.


Author: Tim Moore <timoore@redhat.com>

Effects/model-default.eff

@@ -62,7 +62,7 @@
       </texture-unit>
       <program>
         <vertex-shader>Shaders/model-default.vert</vertex-shader>
-        <fragment-shader>Shaders/model-default.frag</fragment-shader>
+        <fragment-shader>Shaders/default.frag</fragment-shader>
       </program>
       <uniform>
       <name>texture</name>

Shaders/default.frag

@@ -1,21 +1,27 @@
 // -*-C++-*-
 
-varying vec4 diffuse, ambient;
+varying vec4 diffuse, constantColor;
 varying vec3 normal, lightDir, halfVector;
 varying float fogCoord, alpha;
 
 uniform sampler2D texture;
 
+float luminance(vec3 color)
+{
+    return dot(vec3(0.212671, 0.715160, 0.072169), color);
+}
+
 void main()
 {
     vec3 n, halfV;
     float NdotL, NdotHV, fogFactor;
-    vec4 color = ambient + gl_FrontMaterial.emission;
+    vec4 color = constantColor;
     vec4 texel;
     vec4 fragColor;
     vec4 specular = vec4(0.0);
-    
     n = normalize(normal);
+    if (!gl_FrontFacing)
+        n = -n;
     NdotL = max(dot(n, lightDir), 0.0);
     if (NdotL > 0.0) {
         color += diffuse * NdotL;

Shaders/default.vert

@@ -8,7 +8,7 @@
 // Diffuse and ambient colors come from the gl_Color. This is
 // equivalent to osg::Material::AMBIENT_AND_DIFFUSE.
 
-varying vec4 diffuse, ambient;
+varying vec4 diffuse, constantColor;
 varying vec3 normal, lightDir, halfVector;
 varying float fogCoord, alpha;
 
@@ -22,7 +22,7 @@ void main()
     halfVector = normalize(gl_LightSource[0].halfVector.xyz);
     diffuse = gl_Color * gl_LightSource[0].diffuse;
     alpha = gl_Color.a;
-    ambient = gl_Color * gl_LightSource[0].ambient;
-    ambient += gl_Color * gl_LightModel.ambient;
+    constantColor =  gl_FrontLightModelProduct.sceneColor
+        + gl_FrontMaterial.ambient * gl_LightSource[0].ambient;
     fogCoord = abs(ecPosition.z);
 }

Shaders/model-default.frag

@@ -1,37 +0,0 @@
-// -*-C++-*-
-
-varying vec4 diffuse, constantColor;
-varying vec3 normal, lightDir, halfVector;
-varying float alpha, fogCoord;
-
-uniform sampler2D texture;
-
-void main()
-{
-    vec3 n, halfV;
-    float NdotL, NdotHV, fogFactor;
-    vec4 color = constantColor;
-    vec4 texel;
-    vec4 fragColor;
-    vec4 specular = vec4(0.0);
-    n = normalize(normal);
-    NdotL = max(dot(n, lightDir), 0.0);
-    if (NdotL > 0.0) {
-        color += diffuse * NdotL;
-        halfV = normalize(halfVector);
-        NdotHV = max(dot(n, halfV), 0.0);
-        if (gl_FrontMaterial.shininess > 0.0)
-            specular.rgb = (gl_FrontMaterial.specular.rgb
-                            * gl_LightSource[0].specular.rgb
-                            * pow(NdotHV, gl_FrontMaterial.shininess));
-    }
-    color.a = alpha;
-    // This shouldn't be necessary, but our lighting becomes very
-    // saturated. Clamping the color before modulating by the texture
-    // is closer to what the OpenGL fixed function pipeline does.
-    color = clamp(color, 0.0, 1.0);
-    texel = texture2D(texture, gl_TexCoord[0].st);
-    fragColor = color * texel + specular;
-    fogFactor = exp(-gl_Fog.density * gl_Fog.density * fogCoord * fogCoord);
-    gl_FragColor = mix(gl_Fog.color, fragColor, fogFactor);
-}