Help Needed - Modeling gun barrel slots.

Need some help with modeling gun barrel slots.
I can’t think of how to do the topology.




I’m not actually modeling the YAK 3.
This is for a space ship I’m woking on.


What you want to do is make a cylinder for the gun barrel, and use the Boolean modifier to get the intersection of the the cylinder and the hull.

Unfortunately the Boolean script is noted for making a tangled mess of one’s mesh.

Check the 4th and 6th posts, it gives a wireframe view of exactly what you’re talking about.

It’s not a tutorial, but it should be enough to get you started.

experiment with this idea- take one of those faces on the side of your mesh and extrude it keeping it in the same place and (in top view) rotate it so that one side stays flush with the hull, and the other goes ‘into’ the hull. Now remove the doubles that will be present on the side that stayed flush (if you did it correctly). On the opposite side you should have a new face that you created. extrude that inwards to make the “barrel” inside the hull.

Select, e.g., these two lines:

Hit V (Rip) – not sure how to determine which side gets ripped, current loc of mouse? – and drag down/in. Add a couple quads and tris to fill int the empty space. Extrude the new quads inward to make the gun barrel. Shape the fueslage in front of that for the cutout.

here is example of it

i elongated a UVspere then put a tube and apply trhe boolean

look at pic not a bad job at all


here is the final solid model

@ HouseArrest
I don’t get it. Could you post some images
showing in steps the topology?

@ Hobo Joe
To bad the guy has a subsurf mod on with optimal draw on
or I could figure it out.

@ RickyBlender
I tried out the boolean mod and it works.
Problem is, is that it makes a mess and look horrible with smooth on.

There’s got to be a better way to make these slots.

with the quantiy of verticies due to boolean opeation it makes smooth act in a strange way
with this new feature !:evilgrin:

the only way i see is to separate this feature from the rest of the body then you end up with 2 objects independant - you can smooth the rest of the body but not the gun exit part
you can use V key to rip it apart then select and separate with P Key
subdivide will lessen the effect of the smooth but verticies goes way up so not that good!

OK just check for vertex group
use the modifier smooth - this allow you to create a vertex group whitout the gun exit part and then you smooth the vertex group only
that should work check it


I have been curious about this as well and the boolean method doesn’t work well when you want to subsurf. Here is a method that has potential. The approach is to retopo a circle onto the target mesh in a way that will yield a smooth hole that can then be extruded into the gun hole. I’ve included images of the starting mesh (created using a curve, converting to mesh and spinning), a composite of the steps, and the resulting mesh and wire.

  1. The first complication is calculating the size of the circle. The plan is to retopo the circle onto the mesh and create as few triangles as possible. You could use an 8-vertex circle and have no triangles (count the white circles) or use a 12-vertex circle and make a few triangles with the cuts shown by the white lines. Create the circle with retopo off.

  2. After creating the circle, from a side view move the circle along the axis to the front of the target object. Separate the circle mesh (PKEY), TAB to object mode, select the separated circle, TAB to edit mode. Make sure it is positioned “conveniently”, i.e., any rotating and positioning should be done before the retopo step. From the front view, turn on retopo and press Retopo All. Once retopo’d, turn off retopo.

  3. Once the circle is retopo’s onto the object, edit the object to remove the center vertex. In object mode select the circle and the target object and join them (CTRL-J).

  4. If you used an 8-vertex circle you don’t need this step. For a 12-vertex circle, more vertices are needed for the faces surrounding the hole. These are created by subdividing the edges on either side of the hole.

  5. Fill in the faces between the hole and the target mesh. Select the 12 vertices of the circle and the 12 vertices in the mesh surrounding the mesh and face them using FKEY, in the popup menu select ‘Skin Faces / Edge-Loops’. Select all vertices and recalculate normals to outside, CTRL-N.

  6. Extrude the hole. Select the circle, from a side view extrude it horizontally.

The basic hole is complete. For a smooth subsurf you will want to put an edge loop around the hole. One reason for surrounding the hole with quads is to make this part easy. Doing it correctly is interesting to explain but worth learning:

  • CTRL-R to start an edge loop creation and move the cursor until you get a loop around the hole.
  • LMB to place the edge loop. You can get a reasonable edge loop by using the percentage positioning but the following steps can sometimes give better control.
  • PKEY to switch out of percentage placement. You can now use the FKEY to switch control sides (hit FKEY a few times and watch the pink rectangle move from the circle to the surrounding squares.) Stop hitting the FKEY when the pink square is on the circle and create the circle edge loop a small distance from the hole.
  • LMB to lock in the new edge loop

The final image uses a level 2 subsurf and smooth.


g60, that is excellent!

Pretty cool.
I’ve heard of retopo, I think I tried it out like once
and nothing happened because I didn’t
know what I was doing.

The retopo tool can snap a set of verticies to another surface. Comes in real handy if you are, say, trying to cut hatches and port holes into a spaceship.

When I first started learning Blender I tried just about every tool in the box and, at first, didn’t understand retopo. Now I use it all the time, although I never edit with retopo on but prefer to create a shape that will lay over another. The ahem older folks around here might remember a toy called a VacuForm (or some similar name) that could warm a thin sheet of plastic that you have placed over a mold, pulling a lever would create a vacuum and pull the sheet onto the mold. I use retopo in the same way.

Retopo’s cool like that. I’ve used it to make some pipe fittings and stuff recently. I wish you couldn’t ctrl-z it back on after turning it off though. I kept trying to scale a platform in the middle of a room, and having my verts ZYGLOM over to the walls … then I turn retopo off and hit undo … and retopo goes on again. :slight_smile:

Clever technique, G60, retopo is the way to go and produce clean geometry.

I don’t understand what you to say. This picture is not giving full information.

Wide Circles