danini-the-panini/mittsu-opengl

#version 330

uniform vec3 color;
uniform sampler2D map;
uniform float opacity;

uniform int fogType;
uniform vec3 fogColor;
uniform float fogDensity;
uniform float fogNear;
uniform float fogFar;
uniform float alphaTest;

in vec2 vUV;
layout(location = 0) out vec4 fragColor;

void main() {
    vec4 texture = texture( map, vUV );

    if ( texture.a < alphaTest ) discard;

    fragColor = vec4( color * texture.xyz, texture.a * opacity );

    if ( fogType > 0 ) {
        float depth = gl_FragCoord.z / gl_FragCoord.w;
        float fogFactor = 0.0;

        if ( fogType == 1 ) {
            fogFactor = smoothstep( fogNear, fogFar, depth );
        } else {
            const float LOG2 = 1.442695;
            float fogFactor = exp2( - fogDensity * fogDensity * depth * depth * LOG2 );
            fogFactor = 1.0 - clamp( fogFactor, 0.0, 1.0 );
        }

        fragColor = mix( fragColor, vec4( fogColor, fragColor.w ), fogFactor );
    }
}