danini-the-panini/mittsu-opengl

#ifdef USE_FOG

    #ifdef USE_LOGDEPTHBUF_EXT

        float depth = gl_FragDepthEXT / gl_FragCoord.w;

    #else

        float depth = gl_FragCoord.z / gl_FragCoord.w;

    #endif

    #ifdef FOG_EXP2

        float fogFactor = exp2( - square( fogDensity ) * square( depth ) * LOG2 );
        fogFactor = whiteCompliment( fogFactor );

    #else

        float fogFactor = smoothstep( fogNear, fogFar, depth );

    #endif
    
    outgoingLight = mix( outgoingLight, fogColor, fogFactor );

#endif