fragshader.glsl

vec2 invMobius(vec2 a, vec2 b, vec2 c, vec2 d, vec2 z){
    vec2 num = vec2(0,0);
    num.x = (d.x*z.x - d.y*z.y)-b.x;
    num.y = (d.x*z.y - d.y*z.x)-b.y;
    
    vec2 den;
    den.x = (c.x*z.x - c.y*z.y) + a.x;
    den.y = -(c.x*z.y + c.y*z.x) + a.y;
    
    den= den/(den.x*den.x + den.y*den.y);
    
    vec2 result;
    result.x = num.x*den.x - num.y*den.y;
    result.y = num.x*den.y + num.y*den.x;
    return result;

}


vec4 mainImage( vec2 fragCoord )
{
    vec2 uv = fragCoord.xy / iResolution.xy;
    uv = uv- vec2(0.5,0.5);
    uv = uv*3.0;
    vec2 a = vec2(1,1);
    vec2 b = vec2(0,1);
    vec2 c = vec2(0,1);
    vec2 d = vec2(1,0);
    vec2 transCoord = invMobius(a,b,c,d,uv);
    fragColor = length(transCoord)>1.0?vec4(1,1,1,1):texture(iChannel0,transCoord);
}

void main(){
    gl_FragColor = mainImage(gl_FragCoord);
}