fog shader is fixed for the polygon type: it mixes with background co…

…lor instead of decreasing alpha channel

src/cherish/Shaders/Polygon.frag

@@ -4,26 +4,30 @@ uniform bool IsFogged;
 uniform float FogMin;
 uniform float FogMax;
 uniform vec4 CameraEye;
+uniform vec4 FogColor;
 
 in VertexData{
     vec4 mColor;
     vec4 mVertex; // to calculate distance to camera eye
 } VertexIn;
 
-float getFogFactor(float d, float a)
+float getFogFactor(float d)
 {
-    if (d>=FogMax) return 0;
-    if (d<=FogMin) return a;
+    if (d>=FogMax) return 1;
+    if (d<=FogMin) return 0;
 
-    return (FogMax - d) / (FogMax - FogMin) * a;
+    return 1 - (FogMax - d) / (FogMax - FogMin);
 }
 
 void main(void)
 {
-    float alpha = VertexIn.mColor.a;
+    vec4 color = VertexIn.mColor;
     if (IsFogged){
         float d = distance(CameraEye, VertexIn.mVertex);
-        alpha = getFogFactor(d, alpha);
+        float alpha = getFogFactor(d);
+        color = mix(color, FogColor, alpha);
     }
-    gl_FragColor = vec4(VertexIn.mColor.rgb, alpha);
+
+    gl_FragColor = color;
+            //vec4(VertexIn.mColor.rgb, alpha);
 }

src/libSGControls/ProgramPolygon.cpp

@@ -111,6 +111,10 @@ bool ProgramPolygon::addPresetUniforms()
         qCritical("Could not initialize fog min factor");
         return false;
     }
+    if (!this->addUniform<osg::Vec4f>("FogColor", osg::Uniform::FLOAT_VEC4, cher::BACKGROUND_CLR)){
+        qCritical("Could not initialize fog color uniform");
+        return false;
+    }
 
     return true;
 }