Join two plane surfaces


is there anyone who knows how join these surfaces

thank you so much by advance !!


join two surfaces.3dm (2.7 MB)

Hi wskad - do you really want these joined to a zero-thickness line there,

or do you want the purple object to hit the larger one at its full thickness?


You can use ExtractSrf to extract the 2 surfaces and then use join command.
The question is why would you want to do this? Building self-intersecting geometry can lead to problems and isn’t like anything that exists in the real world.

Also some of your surfaces are not quite planar. They have a very small amount of twist which is also likely to trip you up if you if you plan to do more with this.

Hi Pascal,

I want the purple object to hit the larger one at its full thickness


Hi wskad - assuming that you want the purple object, then, to be a sort of continuation of the larger one, I’d go about this a little differently - the big box is slightly tapered to the bottom- that is, the sides are not vertical as the sides of the purple object are - this is going to make the join there a little messy. There are a couple of ways to get at this, if I see what you are after-

  1. ExtractSrf the large face of the larger box.
  2. Make a rectangle on that face that represents the base of the new extension.(red in my file)
  3. Trim the face with that rectyange and join it back to the box.
  4. Make 2 lines that are extensions (Line > Extension) of the edges of the large box (green lines in my file) I’d make them a little longer than you want.
  5. Sweep2, the rectangle on the lines with maintain Height checked.
  6. Trim the object with a plane at the depth you want for it. CutPlane in Right is a good way to get the trimming plane)
  7. Join to the box
  8. Cap to close off the trimmed end.
    (You might want to MergeAllFaces when done to clean up.
    join two surfaces_PG.3dm (178.0 KB)


thank you very much Pascal

I’m trying it tomorrow

Hi Pascal,

I am trying your way and it’s ok. Thank you

So I found too another way (like you have said in your message) and I would like to share on this forum

  1. Solid Tools
  2. ExtrudeCrv > AlongCrv and follow instructions

select surface and

and select curve rail for guide of extrusion

and that’s all

Yep, that works as well - I thought it looked like you wanted the surface to extend the existing edges of the box at the top - if your way looks like you want it to, then perfect!