In this opportunity, we want to share a process that can be useful when developing video games, it is about rigging and animating a door in Blender 4.1, and its subsequent import into Unreal Engine 5.4.
To do this, we took part of the workflow learned in this tutorial: How to rig folding windows/doors with Blender, and adjusted it to our needs for the door animation.
So, let’s get started!
Workspace and modelling
Adjusting the Blender workspace
The first thing to do is to adjust our Blender workspace so that there are no proportion problems when importing our model to UE5. To do this, we open Blender and remove the default elements (the cube, the camera and the light).
Then, entering the Scene Properties section of the right side panel, we set the scale to 0.01 and change the length to centimetres (which is the unit used in Unreal Engine).
After that, we will notice that the reticle of the viewport seems to have disappeared, this is due to the change of units. To correct this, simply press the letter N, and move to the View tab. There we change the Clip Start parameter from 0.01 cm to 1 cm, and the End parameter from 1000 to 10000000000 and we will notice how the grid appears again.
Door Modelling
To start modelling the door, we press the keyboard shortcut Shift + A, in order to create a cube in the scene.
Taking into consideration the size of the characters in Unreal, which are approximately 181 cm high, we can set the size of the door to 215 cm high.
To do this, we go to Edit Mode and by pressing the number key 1; we can from the Front Orthogonal View, raise the cube so that it is just above the X axis, as well as set the height of the cube to the desired size.
Once this is done, we set the thickness of the door at 6 cm and the width of the door at approximately 125 cm. These measurements are to taste and depend on the size that is required according to the type of game that is being made.
Note: Once the dimensions have been set, if this has been done in Object Mode, press CTRL + A and apply the scale.
Subsequently, the necessary modelling details are added.
Rigging and animation en Blender
Door rigging
To start with the creation of the skeleton, we place the door pivot in the bottom left corner and match it to the origin point.
In Object Mode, press the keyboard shortcut Shift + A and select the Armature option.
Once created, we assign the value Radius: 100 cm, because due to the change of Units in Blender, it will be created by default at 1 cm.
In Edit Mode we rotate the bone in the Y axis by 90º, position it and rename it Root.
Duplicate the Root bone with Shift + D and rename this duplicate as Controller, as it will be in charge of managing Root’s movements.
It’s advisable to set the Roll of the bones to 0, in order to avoid erroneous behaviour in the animation.
We relate the Root bone to the geometry. To do this, in Object Mode select the door, and then in Pose Mode select the Root bone. And pressing CTRL + P, we select the Bone option.
In doing so, we can notice that any transformation in the Root bone directly affects the door.
In Pose Mode, select the Root bone, and add the constraint called Copy Rotation, indicating the parameters Target: Armature and Bone: Controller. For this constraint, it is important to set the Target and Owner parameters to Local Space.
Selecting the Controller bone, and accessing Bone Properties, in the Transform section we change the Mode parameter to XYZ Euler. Next, we lock all the Location axes, and in the case of Rotation only the X and Y axes.
To this same bone we add a constraint called Limit Rotation, adding the values Min: 0 and Max: 90º for the Z axis, which is precisely the one we have left unlocked in the previous step. Additionally, we change the parameter Owner to Local Space. This will allow to control the opening of the door at the set angles.
That done, our door is ready to be animated.
Door animation
We go to the workspace Animation of Blender, there we will find the section Dope Sheet, which will allow us to add the keyframes for our animation.
Once there, and being positioned at frame 1, we activate the Auto Keying option.
In Pose Mode, and with the Controller bone selected, go to the Transform -> Rotation section, set the Z axis to 0 and mark the little dot on the side called Animate Property.
We move to frame 15 and change the Z rotation value to 25º. As we had previously selected the Auto Keying option, when we set the value, the keyframe will be marked automatically.
Then, we repeat the previous action in frame 20.
We move to frame 40 and change the Z rotation value to 85º. There we can see that even if we place a value higher than 100º, the door will not rotate beyond 90º, which was the limit we set as the maximum.
Next, we move to frame 60 and change the Z Rotation value to 0º.
This will result in an animation that initially shows a partial opening, then opens fully according to the angle we set, and finally closes.
To save the animation, click on the Action Editor option and from there give a name to your animation, marking the shield icon next to it.
Export from Blender
With the elements selected in the viewport, select File -> Export -> FBX.
Note: To export the door with collisions, you can consult our previous post: Blender room with collisions for UE5.
Once the export window is displayed, select the following options:
Note: Take into consideration that in the Transform section, the axes of the bones are set (this is the way we got the animation to work correctly in Unreal).
In the Armature section, we deactivate the Add Leaf Bones option and leave Bake Animation activated.
Import into Unreal Engine
With the engine open, and having created a third person project, we go to the Content folder and from there we press right click, and then select the Import to /Game option.
Select the fbx file and click on the Open button.
In the window that appears, check the Import Animations option, and then click on the Import All button. (Although some warnings may appear during the import, they do not affect the functioning of the animation).
If we drag the file called Animation Sequence onto the scene, we will see that our animation runs smoothly.
You can see the process of animating the door and importing it into Unreal Engine here:
And that’s it, we hope that in some way this information can be useful. There are always different ways of doing things and new techniques to discover, so it would be interesting to experiment and adapt this process to different situations.
Thanks for reading, see you next time!
