varying vec3 vColor;
varying vec2 uv;

uniform sampler2D tex;
uniform vec2 resolution;
vec4 HmdWarpParam = vec4(1.4, 0.22, 0.24, 80);

void main(void)
{
    float x;
    float y;

    float rSq;

    vec2 theta = vec2(x,y);

    theta.x = gl_FragCoord.x / resolution.x * 1.7;
    theta.y = gl_FragCoord.y / resolution.y;

    if(gl_FragCoord.x > resolution.x / 2.0)
      theta.x -= 0.7;

    theta.x -= 0.5;
    theta.y -= 0.5;

    rSq = theta.x*theta.x + theta.y*theta.y;

    vec2 rvector;
    rvector = theta * (HmdWarpParam.x + HmdWarpParam.y*rSq + HmdWarpParam.z * rSq * rSq  + HmdWarpParam.w * rSq * rSq * rSq);

    x = rvector.x;
    y = rvector.y;

    rvector.x+=0.5;
    rvector.y+=0.5;

    rvector.y = 1.0-rvector.y;

    if(rvector.x >= 0.0 && rvector.y >= 0.0 && rvector.x <= 1.0 && rvector.y <= 1.0) {
        gl_FragColor = texture2D(tex, rvector);
    }
    else {
        // red
        gl_FragColor = vec4(0.0,0.0,0.0,1.0);
    }
}