#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;

        FragColor = vec4(color, 1.0);
    }