When converting 2d pixel point to world coordinates, why is 0.5 added

[NagabhushanSN95]

In https://github.com/jmccormac/pySceneNetRGBD/blob/master/calculate_optical_flow.py#L22-L23, why is 0.5 being added to x and y?

[ankurhanda]

to make sure the ray passes through the center of the pixel and not the top-left corner.

[NagabhushanSN95]

No here, x is in the range 0 to width i.e. 320. For x=319, adding 0.5 doesn't make it at the center, right?