[Help] Asymmetrical hole pattern on cylinder / Shell modifier issue

[such8]

I'm trying to model a gun barrel that has holes in it. Here's how the real thing looks: 

Here's my approach to modelling it:

I have the hole pattern, which looks like this:

Then I made an editable poly object that matches this pattern:

Then I added a bend modifier with a 360 degree angle to make it a cylinder:

And finally, I've added a shell modifier to add some thickness to the barrel:

 

Looking good, right? Well for the most part, yes, but the shell modifier doesn't exactly behave the way I'd like it to. This is how it looks from the top:

The two selected loops should be on top of one another, but as you can see, that is not the case. The upper edgeloop looks like as if it were scaled up on its X axis. (However, I didn't scale it, this is the result the shell modifier produced.)

Any ideas how I might be able to fix this? Aligning the vertices by hand isn't really an option as there are way to many of these holes for that. 

I have attached a .max file (2016 version) containing this barrel section.

[Daf]

Hi,

Have you tried checking the "Straighten Corners" box at the bottom of the modifier panel? I'm not where I can try this - so not sure if that would work for you in this case.

Daf

[blakestone · Accepted solution]

I only have 3dsMax 2015 so I couldn't open your file however this is how I would do it .
I have attached my MAX file (requires 3dsMax 2012 or higher to open).

Because the model is symmetrical I only work on a small piece.

1. I take my template and bend it 360 degrees then delete half of it.

2. I then select the holes and CAP them then EXTRUDE them (I used the value 0.5)

3. I then clone my model and delete the extruded section and then apply a SHELL modifier (to create the mesh inside) and delete all other faces.

4. I position the inside mesh inside my original mesh and then SNAP the vertices to fit the original model

5. I then attach both pieces and weld all vertices so I have a single mesh again.

6. I use the MIRROR tool to MIRROR and flip the mesh

7. I then attach ARRAY to the desired length of the barrel.

Hope this helps!

[such8]

---

@daf wrote:

Hi,

Have you tried checking the "Straighten Corners" box at the bottom of the modifier panel? I'm not where I can try this - so not sure if that would work for you in this case.

Daf

---

Thanks for the tip, I've just tried it out. It helps a little, but doesn't completely solve the issue.

[such8]

---

@blakestone wrote:

I only have 3dsMax 2015 so I couldn't open your file however this is how I would do it .
I have attached my MAX file (requires 3dsMax 2012 or higher to open).

Because the model is symmetrical I only work on a small piece.

1. I take my template and bend it 360 degrees then delete half of it.

2. I then select the holes and CAP them then EXTRUDE them (I used the value 0.5)

3. I then clone my model and delete the extruded section and then apply a SHELL modifier (to create the mesh inside) and delete all other faces.

4. I position the inside mesh inside my original mesh and then SNAP the vertices to fit the original model

5. I then attach both pieces and weld all vertices so I have a single mesh again.

6. I use the MIRROR tool to MIRROR and flip the mesh

7. I then attach ARRAY to the desired length of the barrel.

Hope this helps!

---

Wow, thanks a lot, I've just loaded up the max file you've attached, and that is exactly what I was looking for. But I'm having trouble recreating it using your method :(. 

My first issue is that the model isn't symmetrical:

 

As you can see, the angle between the green and the yellow line is smaller than the angle between the red and the yellow line.

This is what it would look like if it were symmetrical (the lines are in the same position as in the previous image):

This symmetrical version is something I could probably get away with, but I'd like to make this model as accurate as possible, so I'm going to stick with the asymmetrical version.

Leaving out the cutting in half and mirroring parts, I followed your instructions, but I just can't figure out step 3.

I have capped the holes and made an extrusion:

Then I cloned the mesh and deleted the extruded parts:

And, again, it is the shell modifier I'm having problems with. When I add the shell modifier (to the cloned mesh, right?) it gives me the same result as I got when I tried modelling this using my own approach.

Shell modifier added to the cloned mesh:

But I have the same problem:

I feel so dumb for not being able to follow instructions. I have reattached the .max file, now compatible with Max 2014 and up. 

You can get the hole pattern image from imgur.

[blakestone]

I think it looks off due to the particular pattern. I have redone this and left all the Edit Poly modifiers so you can see how its created, you can see in the attached image it all aligns. Hope this helps

[such8]

Thanks a lot Blakestone, now I see what you did. Yeah, that pattern is a bit tricky, but now it's all good.