After intersecting (knife) two surfaces that didn't exactly match, I'm left with a vertical wall where the cut was made (circled in red). What can I do to "remove" the wall? Concretely, I would like the vertices of one "lip", say the upper one, to be projected on the lower lip, so that the vertical faces can be safely removed.

What I tried (and why I'd rather not go that way)

Bridge edge loops: it wouldn't work because the vertices don't match. As you can see, the upper lip has more vertices.

Resizing along edge orientation: I could select a pair of vertices that defines an edge in the lower lip, define a transform orientation, select vertices in the upper lip that are above the edge and resize their transform Z (or another fitting axis) to zero. While it would surely work (I don't need adjacent faces to share every vertex, I think), it would be long and tedious, and error prone too. In this case I have four edges, but what if I had a similar case along 50 edges?

enter image description here


Here is a Blender file with a scenario similar to mine.


To avoid the XY problem, I'd better describe in more detail how I came to the problem. Maybe I can work in a different way.

I have two lines - say they're the border of two converging roads. I wish to join them with a smooth surface (but I want to be able to model it, i.e., it should not be "the mathematically smooth" surface).

My approach was to extrude from those edges, along the edge normal, so to "continue" the road surface, then I would intersect knife them. However, one of the roads is the main one, and its extrusion must have a minimum width. In the screenshot above, the green quads are the road side extrusions, and the one in the lower part of the image is the main one.

Look at the following picture: the highlighted line is the main road border. The z axis is exaggerated.

enter image description here

I extrude the road sides:

enter image description here

Now I need to join the two inner edge loops. What I did above is extruding the secondary one towards the first, then knife it using the main border's extrusion along Z. However, this gave me bad topology. Nxdhin2005's process gives me a good mesh, but it would be hard to match the other border just by adjusting the extruded one.

Maybe I'm overthinking this, and I should just bridge the two edge loops, then add detail on the new faces, maybe by sculpting?

  • $\begingroup$ Have you tried merging the vertices $\endgroup$
    – Nxdhin
    Commented Aug 4, 2020 at 10:16
  • $\begingroup$ @Nxdhin2005 Sure, but not all the vertices of the upper lip have a matching vertex in the lower lip, and I would like to retain the quad formation if possible. $\endgroup$
    – Simone
    Commented Aug 4, 2020 at 10:37
  • $\begingroup$ @Nxdhin2005 No :) But I can share a similar, minimal file. See the edit in the question. $\endgroup$
    – Simone
    Commented Aug 4, 2020 at 12:57
  • $\begingroup$ I saw you .blend file.. Your topology of the mesh is pretty screwed up .I guess you have knife projected the edges of the mesh onto the vertical wall .I can assure you that it is not the right way to join two mismatching mesh. You have overlapping edges and the mesh lacks continuity of vertices. I don't even have the slightest idea on how to clean it up. : ( . I hope some other community member can help you :) $\endgroup$
    – Nxdhin
    Commented Aug 4, 2020 at 13:32
  • $\begingroup$ @Nxdhin2005 Exactly, I did exactly that, followed by a remove doubles (or knife mode "Merge"). What should I do instead? My goal is to join the two surfaces along a certain vertical line (hence the intersection knife), with one of the two surfaces imposing its profile to the other one. What are other ways to achieve that? $\endgroup$
    – Simone
    Commented Aug 4, 2020 at 13:44

1 Answer 1


Here we go :

Before anything, I used your .blend file as the reference. Start off by adding in a plane and add in about 10 loopcuts.enter image description here

Select the bottom edges and extrude it along the X-axis and select the end edges and use the shear tool to make that slanting edge.Tweak it a little bit(I didnt select the last vertex before extruding, to match your mesh.) enter image description here Select any vertex in the subdivide portion of the mesh and Use the proportional editing tool to match the mesh to imperfect one.Do a some tweaking and you'll get this: enter image description here Select the edges as shown in this image...

enter image description here Extrude it downwards and scale in it on the z-axis by S +Z and 0 enter image description here Now extrude it on the x-axis again to make the base. Now you have the mesh with perfect topology. However you might have to flip the normals of certain faces with Alt+N >and flip Normals. enter image description here Don't delete your previous mesh. Use it as the reference to make this mesh (just like retopologizing)

  • $\begingroup$ First of all, thank you for all your work - great explanation! However, this still gives me a step with a vertical wall, which I want to get rid of. Besides, I can't freely place the vertices as you did in picture 2 and 3, because they have to match another existing line. I'll clarify my needs in the question - sorry if I wasn't clear. $\endgroup$
    – Simone
    Commented Aug 4, 2020 at 20:44
  • $\begingroup$ You are welcome : ) . I still quite don't understand what you want to merge.I thought wanted to make a similar mesh like that but with a good topology. If you are referring to the plane that we started with as the ' vertical wall ' just select those faces and delete it. $\endgroup$
    – Nxdhin
    Commented Aug 5, 2020 at 5:30
  • $\begingroup$ If I delete those faces, I'll be left with the wavy part and the flat part having a matching topology when looked from above, but they're actually discontinuous, and the step would remain. I wish for one of the two parts (say, the flat one) to follow along the other's edge. $\endgroup$
    – Simone
    Commented Aug 5, 2020 at 6:54

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .