Constant openhmd_rs::shader_distortion_frag

pub const shader_distortion_frag: &'static str = r#"
version 120

//per eye texture to warp for lens distortion
uniform sampler2D warpTexture;

//Position of lens center in m (usually eye_w/2, eye_h/2)
uniform vec2 LensCenter;
//Scale from texture co-ords to m (usually eye_w, eye_h)
uniform vec2 ViewportScale;
//Distortion overall scale in m (usually ~eye_w/2)
uniform float WarpScale;
//Distoriton coefficients (PanoTools model) [a,b,c,d]
uniform vec4 HmdWarpParam;

//chromatic distortion post scaling
uniform vec3 aberr;

void main()
{
    //output_loc is the fragment location on screen from [0,1]x[0,1]
    vec2 output_loc = vec2(gl_TexCoord[0].s, gl_TexCoord[0].t);
    //Compute fragment location in lens-centered co-ordinates at world scale
	vec2 r = output_loc * ViewportScale - LensCenter;
    //scale for distortion model
    //distortion model has r=1 being the largest circle inscribed (e.g. eye_w/2)
    r /= WarpScale;

    //|r|**2
    float r_mag = length(r);
    //offset for which fragment is sourced
    vec2 r_displaced = r * (HmdWarpParam.w + HmdWarpParam.z * r_mag +
		HmdWarpParam.y * r_mag * r_mag +
		HmdWarpParam.x * r_mag * r_mag * r_mag);
    //back to world scale
    r_displaced *= WarpScale;
    //back to viewport co-ord
    vec2 tc_r = (LensCenter + aberr.r * r_displaced) / ViewportScale;
    vec2 tc_g = (LensCenter + aberr.g * r_displaced) / ViewportScale;
    vec2 tc_b = (LensCenter + aberr.b * r_displaced) / ViewportScale;

    float red = texture2D(warpTexture, tc_r).r;
    float green = texture2D(warpTexture, tc_g).g;
    float blue = texture2D(warpTexture, tc_b).b;
    //Black edges off the texture
    gl_FragColor = ((tc_g.x < 0.0) || (tc_g.x > 1.0) || (tc_g.y < 0.0) || (tc_g.y > 1.0)) ? vec4(0.0, 0.0, 0.0, 1.0) : vec4(red, green, blue, 1.0);
}
"#