Chapter 13: Robot Joint Setup and Skinning in Blender

In the previous chapter, we completed a very simple skeleton for the Alien Plant. Now, we can move on to something a bit more complex. The robot character has more independently moving parts, and it also has an arm that will need a better control system than just rotating joints when we come to the rigging and animation parts later in this book. Creating the skeleton for our robot will be very similar to what we did in the previous chapter; however, here, we need to pay a bit more attention to our joint orientations and local axes of our bones/joints. This will be explained in more detail later in this chapter.

The robot is a rigid metal body, so the way we will do the skinning will be a bit different from the previous chapter, but in some ways much simpler.

In this chapter, we will cover the following topics:

• Creating a skeleton for the robot
• Checking and editing the local joint orientations of the joints
...

Technical requirements

You need to have Blender installed, which can you get for free at https://www.blender.org/ (at the time of writing). The Blender version that's being used in this chapter is 3.1.2, but some older and newer versions will also work.

You also need to have a basic understanding of how to navigate the 3D user interface. If you've skipped ahead, then please go back to Chapter 1, An Introduction to Blender's 3D Modeling and Sculpting Tools. If you want further tutorials on how to use Blender, then https://www.blender.org/support/tutorials/ is a great resource.

Finally, you should have completed Chapter 12, Alien Plant Skinning in Blender.

The files related to this chapter are placed at https://github.com/PacktPublishing/Unreal-Engine-5-Character-Creation-Animation-and-Cinematics/tree/main/Chapter13

Creating a skeleton for the robot

To create a skeleton for the robot, we will begin where we began in the previous chapter when we worked with the Alien Plant model.

Opening, positioning, and scaling the robot

Open the Blender file of the robot you created in Chapter 2, Modeling a Robot Drone Character. If you didn't do this, open the completed robot model file that accompanies this book: https://github.com/PacktPublishing/Unreal-Engine-5-Character-Creation-Animation-and-Cinematics/blob/main/Chapter13/RobotDrone_Blender_File.blend. Check that the scale and positioning of the model are correct and that the model is in the center of the scene. We want a model that is around 40-50 cm tall for our final scene, so use the Measuring tool to check this. If you have any trouble remembering how to do this, please refer to Chapter 11, Alien Plant Joint Setup in Blender, the Positioning and scaling the Alien Plant section, as shown in the following screenshot:

...

Checking and editing the local joint orientations of the joints

We've completed our robot skeleton, just like we did for our Alien Plant in Chapter 11, Alien Plant Joint Setup in Blender. However, there's a difference between our Alien Plant and our robot. Later in this book, we will use an inverse kinematics (IK) animation controller on our robot arms. Don't worry about what exactly an IK controller is at this point. We will get to that later, in Chapter 15, Creating a Control Rig with Basic IK Controls for the Robot in UE5. All you need to know for now is that our Bone Orientations and Local axes need to be set in a certain way for our robot arm to animate correctly with an IK controller.

In general, it's good to have clean and sensible bone orientations, so this is very important to be aware of and understand. Next, we will find out what they are.

What is the local orientation of a bone?

To see the local orientation of a bone visually, we do not have...

Skinning the robot to the skeleton in a rigid way

In the previous chapter, we learned how to paint the skin weights with the Skin Weight Painting tool. However, there's also another more direct and exact way to assign specific skin weights to specific vertices on our 3D model. In the case of our robot, this is the perfect situation to try this method.

Our robot has rigid, solid, and unbendable separate moving parts. In this case, we know that every moving part will have to follow their bones 100%. Rather than weight painting each part at 100% after assigning Automatic Skin Weights, we will do so in a different way to speed up the process.

As always, let's make sure our model is ready before we skin.

Preparing the model and collapsing modifiers

If parts of the robot model have modifiers applied to them, such as Mirror, it may complicate how we select the vertices for our skinning process, we need to remove them. To find out if you have modifiers on any of the...

Summary

In this chapter, you learned how to create a more advanced skeleton and check its joint orientations. You learned how to edit those orientations in case you need to in the future. Finally, you learned a more exact and direct way to assign skin weights that is particularly useful for rigid skinning.

This is the last chapter of this book that we'll do in Blender. From now until the end, we will do almost everything in Unreal Engine 5 (UE5). In the next chapter, we will learn how to rig our models in UE5 to make them easy to animate.