Exact modeling: Reach face with edge


Is there any simple method for the above random line to reach the random plane exactly where they should meet?

Recently i’ve come across the need many times to reach a face (a certain plane) with an edge ( a certain line) . the best method i’ve found was to:

  • set up custom constraint along the axis of the line (ctrl+alt+space)
  • go into custom ortho-view of the plane where it appears as line (num 7/1)
  • roughly reach manually by the looks. (G+z)

Also tried at some point with over-lengthing the edges and using boolean but that usually doest work with something more complex than the above simplified problem.

This problem could also be solved for me, if i could do an exact slice by a plane.
Without the messy boolean stuff. I mean a straight line cut that is Exactly aligns with a plane.

Problem is, in the view where the cut would be ideal, the Bmesh Knife tool just does not seem to recognize the plane’s points… Is there something i am missing when doing this, or is it just not possible yet?

(i’ve joined the plane to the same object the cube is on)

Shrinkwrap modifier has a Project option. Might give it a try. Project Group of vertices along some Axis up to Surface sounds like it.

And +1 to missing Knife stick to vertices. Even if i add geometry to the same object, e.g.,in edit mode add 36 vertices circle to make references for Knife, these added vertices are ignored.

By snapping to faces with the closest (to that face) vertice you can achieve edge just touching the plane. On the attached .blend, Edge2 does just that and Edge1 is there to show an ideal starting position where one end of that edge is closer to the plane than the other. Hold Ctrl while moving the edge since the magnetic snapping isn’t activated by default in this file.
Snapping relies on OpenGL, as far as I can tell, so you may need to change your angle of view, or zoom in, to give Blender a better chance to detect the target. Sometimes you will need to do an approximate snap first, then snap again from there to achieve precision.It is like riding a bicycle: at one moment you stop falling all over the place but you never really know why.


TouchFaceWithEdge.blend (83.5 KB)

Shrinkwrap with projection works great for first problem, Thanks a lot!

IamInnocent: Thanks for the answer, i was aware of this method but didnt find it reliable enough, and cumbersome to work with in situations were extra precision was necessary.

In this file I’ve set a transformation orientation with the face of the quad. In front ortho, I started the knife tool, zoomed in fully on the first intersection between the plane and the icosphere, set a first cutting point there, went to the opposite intersection, set a second point, right click and voila.

Once zoomed in fully, the precision is quite enough for anything. Setting ‘Zoom to mouse position’ on and zoom style to ‘Continue’, all in the User Preferences, Interface and Input tabs respectively, helps to work fast.


knifeCuttingInThePlane.blend (87.6 KB)

Yeah, it requires some practice but it can be quite precise and allow fine positioning. I also thought that it mattered that your edge wouldn’t change length or orientation.

Tried that too, sometimes it really does not want to snap at the right place, and for some reason the angle lock also doesnt want to make a straight cut but guess its practice:)
Thanks for the help. I marked thread as solved.

Edit: Just checked the fresh version and Knife got much better than the latest beta release.
It shows what options are turned on/off, and the angle lock works as it should. :slight_smile:

Yay!.. as they say. :slight_smile: