#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);
}