Make quad face from where two edges will meet?

Question

I can't seem to figure out the right term, but basically I have a mesh like this:

and I want to make a face, but when I press F I get a triangle like this:

When I want it to make a quad like this:

Is there some easy way to do this? My process is usually making the face, subdividing the triangle edge, manually copying the coordinates of the vertex I want to line it up with, and then moving the vertex via entering the coordinates. Is there some kind of 'make vertex where these two edges will intersect' function that I'm missing? I feel like I'm doing this the incredibly long way.

Answer 1

If you have the F2 addon enabled (comes bundled with blender), you can do exactly what you are looking for.

To enable the F2 addon, open up the user preferences with CtrlAltU or File > User preferences. Then in the Addons tab, search for f2. Enable the addon by checking the check box.

Now you can simply select the corner vertex, and press F. Done.

Do note that the addon decides which direction to make the new face based off of the mouse position.

Direction control

If there are multiple ways to create a new quad, the position of the mouse cursor is taken into account. Of the multiple new faces which are possible, the one which will be closest to the mouse cursor (in 2d screen-space) is the one which will be created.

Quoted from the wiki

Further documentation can be found on the addon's home page.

Answer 2

Messing around and Googling a little bit more I think I found maybe a better way to do this:

1. Select the vertex you want to extrude

2. Enable Vertex Snap mode like so (Shift + Tab is the default Snap hotkey)

3. Hit E to Extrude the vertex, then hit the hotkey of the axis you want to extend it along (in this case, I'm extending on the Y axis so I hit E + Y), and then hover over the vertex you want to align it to

4. Now the vertex is there, all you have to do is select the two parallel edges and hit F to create a face

This is quite a bit faster than what I was doing, but I'd still like to see if there's a faster method.

Answer 3

Here's the way I usually accomplish this (though I would love to know if there is an easier way).

1. Take one of the edges and extrude it (with E) to approximately where the end of the new face should be.
   
2. Change the pivot point to Active Element.
   
3. Select the extruded edge and then the vertex to align it with (make sure it is white), and then hit S > Y (or X or Z, depending on which way you extruded the edge) > 0.
   
4. Finally, select the overlapping vertices at that corner and hit Alt+M to merge them.

That seems like a long process in a text explanation, but it really doesn't take too long in practice, though it would be nice if someone knows a faster way. The only other downside is that the face's sides must be orthogonal to the coordinate axes.