#version 330 core
out vec4 FragColor;
in vec3 WorldPos;

uniform sampler2D equirectangularMap;

const vec2 invAtan = vec2(0.1591, 0.3183);
vec2 SampleSphericalMap(vec3 v)
{
    vec2 uv = vec2(atan(v.z, v.x), asin(v.y));
    uv *= invAtan;
    uv += 0.5;
    return uv;
}

void main()
{		
    vec2 uv = SampleSphericalMap(normalize(WorldPos));
    vec3 color = texture(equirectangularMap, uv).rgb;

	// reinhard tone mapping
    vec3 mapped = color / (color + vec3(1.0));

    // gamma correction 
	//float gamma = 2.2;
    //mapped = pow(mapped, vec3(1.0 / gamma));
	
	color = mapped;

    FragColor = vec4(color, 1.0);
}