# What is the meaning of cv::Point::cross()?

I noticed in the headers that `cv::Point`

has a `.cross()`

method returning a `double`

.

Had it returned a `cv::Point3d`

, it would have made sense as the cross-product of two 2D homogeneous points with the last coefficient implicitly being set to `1`

(in this case, if the 2 points were 2D points in the image plane then the results is the 2D *line* passing through them).

In fact, the result of `cv::Point::cross()`

is actually the 3rd element of the 3D cross-product above.

What is the intent and/or geometric meaning of the existing method?

More specifically, is there a projective interpretation for this value, given that 2D points *are* represented by 3-element vectors in projective space?