I am looking for an explanation how to get the screen coordinates at which some 3D point will be displayed. (A more abstract description is: I have some imaginary 3D line, which is not displayed. Think of the screen representation of this line. I want to find the point on this line which is closest to the mouse pointer, assuming it was displayed.)
In the thread http://www.opencascade.org/org/forum/thread_2785/ I found the function ConvertToPlane that projects mouse coordinates into 3D space, and there into a specific plane to be more precise. For this purpose the View class offers the methods Convert() and Proj().
But how can I go the other direction? How do I project a 3D point onto the view plane and then convert it into mouse/screen coordinates? Are some methods available for this calculation?