When you select two vertices, you have the option to type “j” (mesh>vertices>connect vertex) or “f” (mesh>faces>make edge face); in my experience the result of both operation is similar: an edge is created between the two selected vertices; however, similar but not identical: “f” creates the edge, but doesn’t seem to cut the polygon. Does anybody know the difference between the two and how to use them properly? When to use one and when the other?
F will create non-manifold(bad) geometry. In practice, if J cuts the edge you want, use it. Use F to fill in new geometry. Use J to modify existing geometry.
However, I’d love to learn more about these features. I wonder why J doesn’t work sometimes, and F always seems to work, but F doesn’t actually cut the face, while creating the edge, whatever that means.
To the point, I am trying to cut a stairwell from a preexisting ground plane; I created the vertices in the relevant locations, but when I tried to J them, no edges were created; F worked, but the edges didn’t cut the geometry (I didn’t know that was possible), almost as if F created some kind of “virtual edges”; and I cannot understand why sometimes J doesn’t work at all. Is that a bug?
Of course I realize I can do the hole in several ways (boolean, knife project, …), so that’s not the issue; I am just curious about these elusive J versus F features.
If someone could clarify further the concept behind both tools (or direct me to useful information) I’d greatly appreciate it.
Yes, wondering and asking questions outside the actual problem without providing support files is a common bug, just not in the program.
You’ve already spelled out the difference in the first post. F fills and J cuts. If it doesn’t for you, show what doesn’t and post a .blend and someone might be able to point out why before the 20th post of guessing and pondering. And if it’s a program error, others can use the file to help testing it on their system and comment on your bug report you link to.
When you say F fills and J cuts, that’s exactly what the documentation says, but I don’t quite understand; like the previous comment that J is manifold; it all sounds really interesting and I wish someone could explain that in detail; I couldn’t find information about it anywhere.
Concerning the problem, I wasn’t trying to turn this into a never ending troubleshooting thread at all; but rather, as I explained in my previous post, the problem was only a trigger to make me wonder about these two features, and its purpose was merely learning more about them; I thought the “Modelling” section was suitable for my question; is there any other section to place this kind of question? Please let me know.
Blue: vertices connected with fill (F)
Green: vertices connected with vertex connect path (J)
Fill doesn’t cut, it makes a new edge between two selected vertices without cutting existing geometry (1), even when the vertices share a face (2). The faces are intact, as shown by the small face indicator dots. But, now there are overlapping edges that are connected but not part of the surface that describes a solid, which makes the whole non-manifold. There are mesh errors, which the overlapping and connected edges create.
Doing the same with vertex connect path finds a straight line on the connected geometry between the vertices, cutting any faces and edges between them (3), or just the shared face (4). The mesh is still manifold, because the new edges are part of the surface that describe a solid, it’s just now done with more faces.
Thanks a million for your response and clear illustration of the issue: exactly the information I was looking for; which, by the way, still I cannot find anywhere other than here in your response (the info about it in Blender Manual and elsewhere is at least spotty).
