glproj = `
x /= ${projection.coefficient().toFixed(10)};
float rho = sqrt(x * x + y * y);
if (rho > ${Math.sqrt(2)}) {
transparent = true;
} else {
float c = 2.0 * asin(rho / 2.0);
float sinc = sin(c);
float cosc = cos(c);
lambda = atan(x * sinc, rho * cosc);
phi = asin(y * sinc / rho);
}
lambda *= ${projection.coefficient().toFixed(10)};
`