How do I create a pocket in an irregular shaped object?

How do I make a pocket in a face that is irregular shaped?

I tried what I thought was the obvious, since the surface that I wanted to do it in wasn’t flat I figured that I would draw it in a separate space and push it through the model and then intersect… since I wanted to trace an existing shape in the model, I tried drawing a rectangle in front of it to draw on, set it to a parallel projection made turned x-ray mode on so I could see the shape of the I wanted to make through it and tried to draw it, but no matter what I tried it would try to draw the lines in the original model.

Longer version: I’m trying to 3D print a sword (possibly just the hilt) for my kid’s halloween costume. I haven’t quite found what I wanted, but I found one with a hilt that I really like (actually for the most part the whole sword is OK, but I really don’t like how it was broken up for printing and some other details). I decided that I’d load up the STL, got that cleaned up, deleted the blade which made a hole in the front of the hilt. Since the front of the hilt is a faceted curved surface I can’t just connect the lines for the hole and I would like to make the blade profile hole (or something really close to it) a pocket in the front of the hilt, but i can’t seem to do it:

I included the skp just in case it helps:
PirateSword.skp (1.5 MB)

Draw the section of the blade out in front of the hilt

Extrude the blade section into the hilt.

Select the blade extrusion and the front surfaces of the hilt. Right click. Choose Intersect Faces>With Selection.

Erase what isn’t the socket and correct the face orientation.

Due to the size of the blade and the hilt, I expect you’ll need to add a tang to the end of the blade to extend into the handle for strength.


@DaveR , it seems like you skipped by a few crucial steps!

  • How did you draw the profile of the blade to match the hole in the original model (which was a major part of @Silverback 's question)? He was having trouble tracing the shape onto a plane in front of the hilt.
  • How did you close over the hole in the front of @Silverback 's model so that you could do the intersection?

I was working from the probably erroneous assumption that the original hilt didn’t have the hole. Since I only had his SKP file to work with, I didn’t know.

So I created the section of the blade using Didier Bur’s Projection extension from SCF to project the edges of the hole onto a face in front of the hilt. Then I extended all those lines on the surfaces of the hilt to the centerline using the Line tool.

I would have put a vertical face in front of the hilt and “projected” the edges on it by simply clicking on the corners of the hole in the hilt with the Pen tool with “on face” inference locked. No need for a plugin.

Yes. That would be another way. The extension was faster. :wink:

This is what I tried to do with no luck, how do you lock the “on face” inference? I’m assuming that once you do you use xray so you can see through the face?

Ding, ding ding… we have a winner. Lol.

Yea, I had no idea how to approach that.

Dave, I’m not sure I’m following you.

The skp that I posted had a hole in the front face of the hilt, so it “had a hole,” unless that’s not what you meant by that.

The original design gave me 2 choices, a sectioned STL that was sectioned in weird places (the hilt is in 2 parts, with the blade sticking out about an inch out of the front of the front part which didn’t make any sense to me at all since if I was going to print the blade I would print it out of different plastic), or a full model.

In this example I used the full model so I wouldn’t have to reassemble the hilt and then deleted the blade leaving the hole.

I’m going to have to load the extension and see if this makes sense trying to do it…

and now I’m even more confused by your “since I only had his SKP file to work with, I didn’t know,” since mine has a hole in the front of the hilt. I have no idea how you closed a hole in the front face of a curved and creased surface.

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That’s why I asked! I managed to close the hole by drawing edges, but it was a quite tedious process and revealed some quirky out-of-plane issues and small edges. So I wondered if there was a better/faster way.

To recreate the shape for the slot without using a plugin, I drew guide lines parallel to green axis through the main vertices of the hole. Then I drew a rectangle in the red-blue plane in front of the hilt. Finally, I drew lines to connect the places where the guide lines pierced the plane. That process is actually easier and faster than it might sound!

Yes. I could very clearly see the hole. I assumed you had made it in the face so I figured I was working backward a bit to get to the point where I could put the socket in. Apparently I was wrong.

Yes. I know your SKP file had the hole in it. I had no idea whether the STL file you started with had a hole or not.

You can use the Projection extension or not. It’s up to you. This is how it looks.


Apologies for getting involved with this. I didn’t mean to create so much trouble.

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Nice solution, DaveR. Very elegant and well explained.

I’m hoping that’s sarcasm, if it’s not I’m sorry for giving you the impression that you’re being a problem. Honestly, I really appreciate when you get involved because you always have good answers. I’ve mentioned this before, but on the 3D printing forums people are repeatedly shocked how I can whip these things up, but any time I hit something a little bit different I end up here and a few of you guys here, especially you make it look really simple and usually get me understanding pretty quickly. In this case, I truly didn’t understand how you got from point A to point B even though you answered my question.

(and I fully believe that I might be off in my writing, the highlights of my last few weeks, especially this weekend are that my dog died, my FIL died and it looks like the coroner will be involved, my truck broke, my 5y/o twins… well needed all the things 5y/o need constantly while the rest of this was going on, and it’s 2 days before Halloween and I have nothing done I promised besides the hook that I asked about designing a couple of weeks ago and I’m just finishing up my kid’s parrot for his shoulder. I’m a little stressed)

how do you do this? I’m googling through some stuff but I’m not finding it.

Well, I’m getting there.

I have not figured out the on face inference thing but I did figure it out with the plugin. While I was at it I slightly oversized the socket so everything should fit well:

I am sorry I haven’t yet got to making those cool GIF animations others here do so I just have to try to explain:

  • make a face for the “projection”
  • Turn on X-ray mode or switch to a viewpoint where you can see both the “original” and the “target”.
  • pick the Line tool. Place it on the “target” face. Don’t click.
  • when the “on face” inference label appears, press and hold down Shift
  • now, still holding down Shift, click on endpoints in the “original”. The edges created will be projected on the face.

This is a technique I use when, for instance, modelling from imported DWG plans or elevations, especially if they are not drawn by myself. It is often quicker to re-draw the thing this way than to try to troubleshoot slight misalignments and nonplanar lines in the original.

You could also make a rectangle while inferencing the points on the sword.
Select rectangle tool, hoover over a startpoint, move to front of sword and press left arrow to draw it in one plane (Green), for the second click, hoover over the opposite point on the sword.

Sounds to me like you need a couple of things:

  1. Make the object a Group. Make your other object a Group. Check info on both, to make sure Sketchup recognizes them as a Solid. Then, when you push one in to the other, geometry will not get messed up.

  2. Get Sketchup Pro. One of the few things that are unique about Pro is the ability to subtract one shape from another, using the Eneroth tools, which cannot be added to Sketchup Make.

Here, I made a box, and made it a Group. I made a rod, and made it a Group. Shoved the rod halfway into the box. Used Subtract…

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