#version 110

#define PI 3.141592653589793238462643383279
#define HALF_PI 1.5707963267948966192313216916398

uniform samplerCube cubeMap;

//whether or not to flip the image
uniform int flip;

//direction correction in radiants
uniform float yawCorrection;
uniform float pitchCorrection;

void main() {
    float x = gl_TexCoord[0].x;
    float y = gl_TexCoord[0].y;

    if (flip == 0) {
        y = 1.0 - gl_TexCoord[0].y; //image is flipped by default. unflip it.
    }

    vec2 textureCoordinates = vec2(x, y);
    vec2 thetaphi = ((textureCoordinates * 2.0) - vec2(1.0)) * vec2(PI, HALF_PI);
    vec3 rayDirection = vec3(cos(thetaphi.y) * cos(thetaphi.x), sin(thetaphi.y), cos(thetaphi.y) * sin(thetaphi.x));

    gl_FragColor = textureCube(cubeMap, rayDirection);
}