Determining slopes of lines in perspective projection Suppose I have parallel lines running along the ground (into the horizon). If I have a camera and I know its tilt angle, is there a way to calculate the slopes of the lines as projected to the 2D image plane? That is, the green angles:



However, the distance from the lines are not known. What parameters of the camera are used in the calculation?
You definitely need to know distances and angle of view of the camera.  For example, if you add lines that are slightly further apart, they will be at different angles.  Like a multi-lane highway.