I have a question about the formula in the official documentation.
You can find the formula in ink below:
This is the formula about distorted point coordinates conversion into pixel coordinates:
x' &= (\theta_d / r) a ~~~ & ~~~ (1) \\
y' &= (\theta_d / r) b ~~~ & ~~~ (2) \\
u &= f_x (x' + \alpha y') + c_x ~~~ & ~~~ (3) \\
v &= f_y y' + c_y ~~~ & ~~~ (4) \\
I found the source code in link below:
And this how the source code programed:
double scale = (r == 0) ? 1.0 : theta_d / r;
u = f*x*scale + c;
v = f*y*scale + c;
My question is:
1.what is α in formula(3)?
2.Why the calculation of formula(3) is different from source code?