How to detect line intersection by object using opencv?

Question

C++ / C#

The camera is located perpendicular to the ground at a height of 8 meters. In the frame you can see passing cars (mostly trucks). It is required to determine the appearance of the car in the frame by crossing the line. I am not strong in programming, so I ask you to help not with an algorithm, but with examples, pieces of code.
I don't need to determine if it's a car or not, as it might not fit completely into the frame (very long trucks). You just need to determine that a large object (more than n in perimeter) crossed the line. And that's it.

Answer 1

It is unlikely that OpenCV is needed, it is enough to set up motion .

Answer 2

Since I have been dealing with similar tasks for 7 years, I can say the following with confidence:
The task is specific - the objects are too large, so the usual motion detector from OpenCV with a tracker is most likely not suitable. Therefore, there is most likely no ready-made solution with open access sources. It is quite possible that such problems have already been solved, and more than once in commercial projects. For obvious reasons, the developers most likely will not give it to you for free.
The task seems to be quite solvable. However, there are a lot of nuances that will have to be taken into account in order for the detection of cars to be reliable: they are mainly related to the variability in illumination and the size of cars. To solve these problems, it is desirable to have experience in computer vision, which implies a good knowledge of programming, mathematics and algorithms.