What is "disf" in "PerspectiveGridGenerator.lua"

[tianYue1988]

Hi, I'm trying to replicate your projection work with PyTorch. But I'm confused about the definition of "focal length" and "disf" in your code. That is:

---

focal_length = math.sqrt(3)/2 ?
dmin = 1/(focal_length + math.sqrt(3))
dmax = 1/(focal_length)
for k=1,depth do
disf = dmin + (k-1)/(depth-1) * (dmax-dmin)
baseGrid[k][i][j][1] = 1/disf

---

Please forgive my offense, I have followed your advice and read the appropriate books. I still don't understand how focal length is defined. And in the paper your point that "the minimum and maximum disparity in the camera frame are denoted as dmin and dmax", So who is a disparty, disf or 1/disf? Your help means a lot to me.