Hi Peer, so for making a curve in the view plane, you can set up a script on a keyboard shortcut to set the construction plane to the view plane as described here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2599.8

Then for doing the ray projections, try the attached script. There are instructions on how to install a plug-in command here.

Select point objects before running the ViewRaysThroughPoints command and it will generate rays going from the 3D view's camera point through the selected points.

Once the rays are generated you can then select them and your target object together and run Construct > Curve > Isect to generate points where the rays intersect the object.

- Michael