#version 330

// Input vertex attributes
in vec3 fragPosition;
in vec2 fragTexCoord;
in vec4 fragColor;
in vec3 fragNormal;

// Input uniform values
uniform sampler2D texture0;
uniform vec4 colDiffuse;

// Fog uniforms
uniform vec3 viewPos;
uniform float fogDensity;
uniform float fogStart; // <--- New Uniform: Distance where fog begins

// Output fragment color
out vec4 finalColor;

void main()
{
    // 1. Get the base color
    vec4 texelColor = texture(texture0, fragTexCoord);
    vec4 baseColor = texelColor * colDiffuse * fragColor;

    // 2. Calculate distance from camera to fragment
    float dist = length(viewPos - fragPosition);

    // 3. Calculate effective distance (distance minus the clear zone)
    // We use max() to ensure we don't get negative distance inside the fogStart radius
    float effectiveDist = max(0.0, dist - fogStart);

    // 4. Calculate fog factor using Exponential Squared formula
    // We use effectiveDist so fog only begins accumulating after fogStart
    float fogFactor = exp(-pow(effectiveDist * fogDensity, 2.0));
    fogFactor = clamp(fogFactor, 0.0, 1.0);

    // 5. Define fog color
    vec3 fogColor = vec3(0.47, 0.7, 0.70);

    // 6. Final Mix
    finalColor = vec4(mix(fogColor, baseColor.rgb, fogFactor), baseColor.a);
}