#import "Common/ShaderLib/GLSLCompat.glsllib"

uniform sampler2D m_Texture;
uniform sampler2D m_DepthTexture;
uniform vec4      m_FogColor;
uniform float     m_FogDensity;
uniform float     m_FogDistance;
// Kamera-Frustum (near, far) — wird jeden Frame aus der echten Kamera gesetzt
uniform vec2      m_FrustumNearFar;

in vec2 texCoord;

void main() {
    vec4  sceneColor = texture2D(m_Texture,      texCoord);
    float rawDepth   = texture2D(m_DepthTexture, texCoord).r;

    // Sky-Pixel (Depth-Buffer = 1.0) nicht nebeln
    if (rawDepth >= 1.0) {
        gl_FragColor = sceneColor;
        return;
    }

    float near = m_FrustumNearFar.x;
    float far  = m_FrustumNearFar.y;

    // Depth-Buffer [0,1] → echte Weltdistanz (Meter)
    // Herleitung: z_view = near*far / (far - rawDepth*(far-near))
    float linearDist = (near * far) / (far - rawDepth * (far - near));

    // Normiert auf FogDistance; d=1 entspricht genau der eingestellten Nebel-Distanz
    float d = linearDist / m_FogDistance;

    // Exponential-squared fog (gleiche Formel wie JME FogFilter, korrekte Tiefe)
    float fogFactor = clamp(exp2(-m_FogDensity * m_FogDensity * d * d * 1.4426950408), 0.0, 1.0);

    gl_FragColor = mix(m_FogColor, sceneColor, fogFactor);
}