add fog on skybox

cw 6/shaders/shader_cube.frag

@@ -4,7 +4,26 @@ out vec4 FragColor;
 in vec3 TexCoords;
 
 uniform samplerCube skybox;
+
+
+float near = 0.1f;
+float far = 70.0f;
+
+float linearizeDepth(float depth)
+{
+    return (2.0 * near * far) / (far + near - (depth * 2.0 - 1.0) * (far - near));
+}
+
+
+float logisticDepth(float depth, float steepness, float offset)
+{
+    float zVal = linearizeDepth(depth);
+    return (1 / (1 + exp(-steepness * (zVal - offset))));
+}
+
 void main()
 {
+    float depth = logisticDepth(gl_FragCoord.z, 0.5f, 5.0f);
+	//FragColor = texture(skybox,TexCoords) * (1.0f - depth) + vec4(depth * vec3(5.0f/255.0f, 35.0f/255.0f, 95.0f/255.0f), 1.0f);
 	FragColor = texture(skybox,TexCoords);
 }