opencv - Explanation of rho and theta parameters in HoughLines -

can give me quick definition of rho , theta parameters in opencv's houghlines function

void cv::houghlines (   inputarray  image,     outputarray     lines,     double  rho,     double  theta,     int     threshold,     double  srn = 0,     double  stn = 0,     double  min_theta = 0,     double  max_theta = cv_pi  ) 

the thing found in doc is:

rho: distance resolution of accumulator in pixels.

theta: angle resolution of accumulator in radians.

do mean if set rho=2 1/2 of image's pixels ignored ... kind of stride=2 ?

to detect lines hough transform, best way represents lines equation of 2 parameters rho , theta shown on image. equation following :

x cos⁡(θ)+y sin⁡(θ)=ρ

where (x,y) line parameters.

this writing in (θ,ρ) parameters allow detection less position-depending writing y=a*x+b

(θ,ρ) in context give discretization these 2 parameters