Learn To Use Blender - Part 4


Welcome to Part 4 of this tutorial series teaching you how to use blender. I highly recommend that you read through the entirety of the tutorial from start to finish so that you can pick up details that appear in every section.

Last time we talked about painting an aircraft white, removing decals, and also some steps to remove the previous paint scheme so we can have a base model as close to the original as possible. This blank aircraft will serve as your starting point for nearly every paint scheme you do on this particular aircraft.

Now that you have a blank aircraft it is time to discuss how to cut a paint scheme into your fuselage and also how to determine when you should use a decal or cut the paint into the fuselage.

You can check out Part 1 here.

You can check out Part 2 here.

You can check out Part 3 here.

Cutting A Mesh

When we create a paint scheme for our aircraft, there are two main ways to do so: with decals or cutting into the aircraft mesh. Creating decals is a topic for another lesson, so today we are focusing on cutting the mesh of our aircraft to create a paint scheme. In order to do this, we need to know how to cut faces and edges in blender.

I would like to start by inserting a cylinder to practice on. To do this we use the following menu path:

Press Space Bar -> Add -> Mesh -> Cylinder

This will bring up the following menu. Note that these numbers may be slightly different for you.

You can edit the values of each box by clicking on the boxes in a certain manner. If you click on the arrows on the left or right side of the box, the value displayed will go up or down 1.000 depending on which button you press. The left will reduce the value while the right arrow will increase the value.

Alternatively, for more precise or to change between value that are very far apart, very quickly, you can click directly in the middle of the box which will change it to look like below:

The bottom box that is highlighted in the above two images indicate that the cylinder will have closed ends, rather than be open like a pipe.

I would recommend setting the following values for the purposes of the cutting demonstration:

  • Vertices = 16

  • Radius = 1.00

  • Depth = 6.00

  • Non-Capped Ends

You will get a cylinder that looks something like the one below.

Now that we have a mesh to practice on, we need to know how to cut into the mesh.

  1. Be in Edit Mode

  2. Press "K"

  3. Select one of the options in the image below.


First you must know that only things that are selected can be cut. This helps you control what is being cut so that things you don’t want to cut.

The Cut Path

When using the cut/knife tool you need to create what I like to call a "cut path" this is a series of lines that indicates where you would like to cut. When you begin to define your cut path, left click on any point in the 3D window. You can drag your mouse to another position, left click and continue to define a cut path.

Note how I have ever face selected on the cylinder. This is because we can only cut what we select. Selecting everything is a great way to get mirror-image cuts on both sides of a fuselage for a paint scheme.

Notice where the corner in the cut path has been made. Now compare this cut path to the resulting cut that was made in the image below.

Here you can see that the cut did not go where we told it to go! Well, this is because the cut tools do not cut faces, but rather edges. If you look carefully, you will see that wherever the cut path intersected an edge, there is a division there in the second image. This is very important for every cut you will ever make. To finish off a cut path and create a cut, press enter or return. If you would like to cancel your cut path, simply press escape.

There are some additional features of the cut tool that will be useful for you to know:

  • To create a vertical or horizontal cut:

        • Drag the cut path a significant distance in the horizontal or vertical direction, you can click on the middle mouse button to activate blender's feature to snap the cut path line to a horizontal or vertical orientation based on the direction you dragged the cut path initially.

  • To use an existing vertex as the start point, end point or corner of the cut path:

        • Hover your cursor as close to the desired vertex as possible. Hold down control to snap the cut path to the vertex. The snapping is most noticeable when trying to define a corner or end point of the cut path. It may take a few tries to get the cut path started this way.

Let’s start with the exact knife cut, as it is 100 percent necessary to paint aircraft. I encourage you to experiment with each and every one of these options

Exact Knife Cut

With this tool, it is important to understand how the tool works in order to get what you want from it. While the name is "exact" it doesn't mean that you can simply click anywhere you like to create a cut exactly at the cut path you created. Remember the two images above? those were made using an exact cut tool.

For the most part, it is one of the most versatile cutting methods as we can create unique shapes and custom angles. The one place this fails, however is when we want precision between once or more setups.

One of the most important things to remember when using the exact cut tool is what happens on the back side of the object we are cutting. The cut path you are defining will cut straight into the object from the view you are using to look at the model. This can create unintended results if you create your cut when you are not in one of the major viewpoints (Number pad 1,3,7 and their reverse views).

Here is the original cut, but we are not in one of the major viewpoints!

Midpoint Cut

The midpoint cut does exactly what it sounds like. It cuts any line that it crosses at its midpoint. For a cylinder this will be right in the middle, however if our mesh is distorted, the midpoint cut tool can be somewhat strange. One nice thing about this cutting method is that our cut path does not have to be perpendicular to the edges we want cut. We simply have to cross the edge with our cut path. The images below demonstrate this:

As you can see we can have a simply crazy cut path result in a nice midpoint cut as long as the cut path crosses each of the edges we want to cut.


The multi-cut option is very similar to the midpoint cut in that we can have a crazy cut path. This time, instead of simply putting a single cut through the edges it will put a specific number of cuts equi-distant from each other. When you click on this tool, the a small menu will open:

By clicking on the arrows or you can indicate how many cuts you want to insert. NOTE that the number of cuts is one less than the number of sections that will be created. In the below example I set the number of cuts to 6.

As you can see the crazy cut path resulted in a 7-section cylinder.

Loop Cuts

The final (or first depending on how you look at things) option for cutting the mesh is in loops. While it can sometimes be useful I use it extremely infrequently. It might be several projects between the times I use it. Therefore I do not want to bog you down with this one as it is more complex that the other cutting methods which can also replace it for the most part. If you are interested in learning more about this, you can check out the Blender wiki page about this here.

Cutting Your First Paint Scheme

To be honest, the best thing to do for your first paint scheme is something simple and easy to do. It will get you into the rhythm of cutting and painting. For this first attempt we are going to make a slanted band around the fuselage of the aircraft.

To begin, we will cut two vertical lines into the fuselage to serve as guides. If you desire, you can merge these away at a later point like you did to clean the model up to begin with. You can place them wherever you like, or even use an existing set of vertices.

To do this I used an exact cut and used the middle mouse button method of obtaining a vertical line. You could do the same thing any number of ways:

  • Multi-cut the center portion of the fuselage. Then move the cuts into position

  • Middle-cut the center portion of the fuselage twice and move both cuts into the right position.

  • Exact cut using the vertical constraint from the middle mouse button.

  • Make a random cut at an angle and then scale the cut in the x-direction to 0.

Next we need to create the slanted lines. I used the bottom vertex of the cuts as a base to start with. I used the control modifier for the exact cut to snap the starting point of the cut path to the bottom of the fuselage.

You can see it best in this image how I tried to get the two slanted cuts to be parallel to each other by using the upper end of the vertical cuts. By angling back the same distance I can get a near-parallel cut.

If you wanted to clean up the extra cuts as I mentioned before, you could merge each vertex from the vertical cuts backwards to the slanted cut. By using the vertices on the same horizontal line, you can effectively eliminate the extra vertices from the model. While this may be more important for a higher-quality model, you do not have to do this for a lower quality model unless the lines cause shading issues (which will be discussed later).

Now I select all the faces that are in between the slanted cuts on both sides of the fuselage while still in Edit Mode. Then I switch over to Vertex Paint Mode and select a color and paint it!

I chose a sky blue for this example:

Part 5

You can move on to Part 5 here!

In this tutorial we will discuss when to paint directly into the mesh, and when to use decals. The general process of creating a decal will be covered and the idea of shrink wrapping will be introduced.

Questions or Comments?

If you have any questions or Comments, you can direct them to this topic on ysfhq.com or get in touch with me via my contacts page.