How is it possible for OpenCV to do Epipolar Geometry calculations without the focal length of a camera?

Thanks a lot @lpea

Nevertheless I’m asking for monocular camera. The goal is to draw epilines (thus variable Z). And my main concern was since I need to know the distance Camera-ImagePlane which f to use.

Would be possible to apply the same principle to obtain the triangle sizes and angles between the camera-imagePlane-imagePixelXY.? Using fx for pixel x coordinates and fy for y pixel coordinates and them sum up the angles with the hypothenusas?

Getting closer, thanks a lot!