Need help modeling a circle inset on a slanted surface


I have been stuck on trying to model this specific part of the sniper scope the hole where the bolt sits in specifically. I’m really not sure on the best way to go about this.

First enable the “Mesh: Loop Tools” in User Preferences. Do the square face and subdivide so that you have 8 vertices that will form the vertices inside into a Circle. Select those vertices and Press W (you should see Loop at the very top instead of Subdivide. Select “Circle”

Or you could just do the circle first and rotate to your desired angle and then extrude and left click to cancel to movement, and then press S to scale. select some of the extruded vertices that will form the bottom side of the square and then press S(Scale Z and 0). Do the same to the other sides.

in 2.8 you can add a circle / Cube at any face’s angle In edit mode then keep going!

happy cl

I’d do it the lazy way and use a boolean modifier first. Then merge appropriate vertices and add supporting edge loops.


Could you show me on what exactly you mean? Do you mean adding in a circle mesh and it projects it onto the angle of the object you want? It sounds like it could be a very helpful feature of 2.8

you need to set the cursor on the face then use the transform instead of global
then when you add object it should be set at proper angle

there was a video for that will try to find it

happy bl

might not be directly implemented yet in 2.8

here is another way to do it

You still can project 3D cursor to a surface.

You just have to use 3D Cursor from toolbar to have access to 3D Cursor orientation menu in Topbar.

Choose Geometry.

Just click on surface -> 3D cursor is placed and oriented.

Then, add an object. (There could be an option “align to 3D Cursor” like “align to view” but that means to control all “Add mesh” operators. Currently, there is none. Devs have other priorities.)

So, you have to go to Orientation menu in header of 3DView > Change it from Global to Cursor.

Then, you can go to Object menu > Transform > Align to Transform Orientation.

happy bl

How would you start with this? After seeing your reply I tried but it is just a mess every time. Do I subdivide the object i’m cutting into with the cylinder? I feel like i’m doing something wrong.

I usually try and work out roughly how many edges I’ll need to take the boolean cutter object reasonably cleanly. I’ve made up another quick example.

  1. Base shape and suitable cutter object (I’ve made it show wireframe only)
  2. I roughly add some edge loops in where the cutter vertices will end up on the base object.
  3. Boolean added and applied. Cutter moved or deleted.
  4. ‘Near miss’ vertices cleaned up and merged. I tend to use Alt+M (and merge at last) making sure the stray vertices are merging with the ones made from the cutout shape to keep its shape. The wee inset bottom left shows the kind of thing I mean. The ones I’ve marked red merge with the ones marked green.
  5. I tend to use the Knife tool to do things like cutting in a support loop around the outside of the hole. This leads to more joining and merging vertices. I use double GG as appropriate to even up the distance of the new loop to the hole and then add my Subdivision modifier.

It’s not the best or most efficient way to make something like this. Aligning a circle to the sloped face won’t work in this circumstance as what you actually need is an oval (as viewed perpendicular to the sloped face) :stuck_out_tongue:


And here is another way which was mentioned above by @peterblender. If not sure of what I am doing I turned the screencast keys on. The key is the inset first of the area and scale it down, the size doesn’t really matter as you can adjust the looptool circle feature after the fact. But at any rate this is the steps I used. Also as you can see there are many of ways to create in the 3d world.


There are indeed :slight_smile: Knife projecting a circle onto the slope would also work. I’ll stick to my long-winded way. It’s handy for cutting circles and other shapes into curved objects.


Thank you so much for this breakdown! It helps a lot with the thought process and the work flow which is what i’m really trying to make a good habit of.

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more then one ways in blender

also look into the Fast Carve addon and Boolean addon by Jayanam
seems to work better then internal Boolean

happy bl

Such few options mentioned while there are many

  • Model a grid, inset, make it a circle with looptools, unchecking flatten option on it
  • Model it flat and shear the surface
  • Model it flat, and cut it from the side with various available tools, then fill it
  • Model a slanted surface and project a circle on it either with face snapping or shrinkwrap modifier

Cutting a circle on a surface is not the only option.

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Thank you everyone for replying with different solutions on how to model this! I’m going to experiment with a lot of different ones to try and get the best result.