Featured image of post Cutting Circles Into Geometry

Cutting Circles Into Geometry

One method for cutting circles into geometry in Blender (will work in other 3D apps)

Today we are going to take a look at how you might cut a circle into geometry. Specifically a cube. I will be showing how to do so in Blender but the general idea should work in any 3D Application. Why a cube? This is the easiest, in my opinion, way to learn how to do this before transferring the skill to more complex geometry.

Be Aware This is aimed at those starting out with geometry and Blender. It is probably not the best method to do this but it works. The resulting geometry is decent and works well with subdivision surface.

Starting with a Cube

First up let’s grab our friendly neigbourhood default cube. If you don’t have one (because you customized your start-up file) then grab a cube with shift + A -> Mesh -> Cube. As mentioned we are going to use a cube because it is easy to setup the geometry to cut the circle out.

Subdivide your cube twice: Enter edit mode Tab. Select all geometry A. Subdivide Right click -> Subdivide twice.

While still in edit mode add a circle Shift + A -> Mesh -> Circle immediately change Vertices to 16 via the menu in the lower left of the viewport.

Turn on snapping, select vertex and center.

Rotate and snap the circle to the center vertex of the cube.

Scale the circle so there is enough space to put two more circles outside your current one.

Turn off snapping. Switch to face select mode 3. Delete the faces behind the circle.

Turn on x-ray and delete the back half of the cube.

Add a mirror modifier and turn on clipping.

Go back to vertex select mode 1. Select the entire circle by double clicking a vertex (sometime this is assigned to alt clicking).

Extrude E, right-click to cancel then scale S. Do these steps twice to end up with two extra loops with about equal distance between them. These are supporting loops for subdivision surface.

Join up the geometry of the circle to the verts of the cube. Do this by selecting 4 verts at a time and filling with F.

Select the inner ring of verts again and extrude E backward until it joins.

Add a Subdivision Surface modifier

For Your Information
If you have an issue with black areas around your circle try recalculating normals. To do this press `Alt + N` then select `recalculate outside`.

You can now sharpen edges in places by selecting the edges in edit mode and turning up mean crease.

Alternatively, and my favorite method, is to use a bevel modifier (placed before subdivison). After adding one you can select weight and use the mean bevel weight instead of mean crease.

That’s it. You now have a potentially useless cube with a hole cut into it.

What use it this? As mentioned I think this is useful to newbies wanting to learn how to cut a hole into geometry without using a boolean. Sure, there are other methods, but I think this one is fairly simple and covers a wide range of tools that are useful to know about in Blender.

Ignoring the preperation of the cube, you should be able to used similar steps to add a hole into any geometry. The difficulty will depend on how complex the geometry is.

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