Blender Curved Cuts

For the latest game in development called The Gap I’ve been doing lots of work in Blender. Learning new tricks and speeding up my workflow. Making a curved cut is something I had not done a lot of and in the past I’ve struggled with the knife tool or knife projects. I’ve been using this method to make curved windows and door arches.

Here is a neat way to make a curved cut in an object with considerable control and only a little bit of mucking about.

Basically we are intersecting one mesh with another and bisecting the meshes with a knife cut to make a simple train tunnel shape.

We are going to start with the default cube which has been scaled up to ten and subdivided 7 times.

A subdivided cube

Next we are going to add a Nurbs Curve as a second object. This we are going to manipulate into the shape we want and later convert it to a mesh to intersect with our cube. You could use any other object like a Bezier Curve or a Path would be very flexible. I chose a Nurbs Curve because it was reasonably simple shape.

Add a Nurbs Curve

In Edit mode manipulate the curve into the shape you want, subdividing the points if required. I find that enabling snapping is a good way to start to keep everything the same on both sides of the curve and then turning it off for fine tuning.

Snapping Enabled and Handles

Once you have the shape you want you can clean up the curve (it’s best to have everything on the same plane).

The Curve is Ready for Converting to a Mesh

Once you are happy with it it is now converted to a mesh.

Convert to Mesh

Which is then extended through our cube!

Extended Intersecting Mesh

Both Meshes are Joined (Ctrl + J). Select the one last that you want to keep the name of.

Joined Meshes into one Object

Switch to Face Select mode and then the Mesh is Intersected and cut with the knife:

Then you can simply delete the faces from the Nurbs Curve Mesh and you are left with the nice curved cut.

Select Faces on one side of the cut and Delete
Delete the Faces on the other side of the Cut

Now you can select all the faces inside your nice curve and extrude them into the cube to make a train tunnel 🙂

Face Select
Extrude into the Cube
The Completed Curved Cut

A few final notes. As I mentioned before you can do this procedure with any mesh to make cuts and hollows with intersections. It’s a bit like using the boolean modifier. It’s not great in every situation as it can make a mess of your topology if you are not neat with your cuts and you can be left with some very tiny faces or triangles. But if you line things up nicely and merge your close vector points it’s a pretty simple and handy tool in the kit.

Blender: Simple Dishes Plates and Cups

One game currently in the pipe line is called The Gap. The game is about the gap between the private internal world of personal histories and how they feed and colour perceptions of the present. Esoteric I know right. But basically it’s an exploring game in an urban setting with lots of indoor areas that need indoor props. So I’ve been doing lots of modelling and researching new methods to make life easier when using Blender (which I love).

Part of this research is reading lots and lots of books and one of them was Blender for Animation and Film-Based Production by Michelangelo Manriqu. The book is great and I’d recommend it to anyone using Blender. One method that I had not seen in any other tutorials or books was this one for making complex cone or cylinder based meshes using Bezier circles and curves. Instead of starting with the basic forms and working complex changes on their geometry this method is quick and simple to make complex (and simple) shapes really fast.

It starts like this: Open a new Scene and add a Bezier Curve and a Bezier Circle:

This is the right view (num 3) with the Bezier Curve moved over a bit on the X axis and rotated 90 degrees on the Z. (R key, −90 , Enter).

A Bezier Circle (in orange) and the black line next to it is a Bezier Curve.

Select the Bezier Circle and Click on the little green Bezier Object button from the properties tab on the right.

Open the Geometry and Bevel sections and click on the Object button. Select your Bezier Curve as the Object.

This sets your Bezier Curve as the defining object for the edges and volume of the now filled Bezier Circle.

Set the Bezier Curve as the Object

Now Select the Bezier Curve and move to Edit mode. Subdivide it as much as you want and play with the shape and angle of the curve to get your Bezier Circle to form all sorts of complex shapes.

Once you are happy with what you have you can go back to Object mode and select the Bezier Circle and go to Object -> convert to mesh (or ALT+C Mesh from Curve/Meta/Surf/Text).

Here some examples I did for this post:

Platter with Bevels

I think the Chalice up there shows the power of this method for creating complex small objects very quickly and the relationship between the Bezier Curve and the resultant mesh.

The Gap will not be released for some time yet – years – it’s still early days but I’m really enjoying the process and it’s nice to be doing something personal and meaningful with game development.