Spinning fans on cars

You can find spinning ventilation fans all over the map. You can use one of those and incorporate it into you own mods for anything that spins, for example the cooling fan on a car engine.

Preparation & Theory

Finding a fan

• In WolvenKit's Asset Browser, search for "fan" and set the "Kind" filter to "mesh"

• choose one of the meshes that looks like, you guessed it, a fan. In this case, we'll be using base\environment\decoration\public_utility\vents\tunnel_jet_fan\tunnel_jet_fan_a.mesh.

• Right click on the file and select "Find files using this". Clear the "Kind" filter, right click on the .ent file which uses the .mesh, and choose "Open without adding to project". In this case, we'll be using base\prefabs\environment\decoration\public_utility\vents\tunnel_jet_fan\tunnel_jet_fan_a.ent . The following information will be specific to that file. You'll likely be able to adapt it to whatever file you're using because the basic setup is quite simple.

The .ent and its components

Inside the file, there are three components:

• an entMeshComponent, which points to the .mesh file of the fan we've selected earlier

• a gameTransformAnimatorComponent, which is the thing that makes the .mesh file spin

• and an entPlaceholderComponent, which dictates the position and rotation of the .mesh (rotation here doesn't mean the spinning animation, but rather the angle of the .mesh itself relative to the ground)

You're probably already familiar with entGarmentSkinnedMeshComponents from other mods you've already made, so this tutorial won't go into explaining the entMeshComponent. Related info can be found on the Wiki though. Of note is that the entMeshComponent must be parented to the gameTransformAnimatorComponent. This is done by setting the bindName of the parentTransform of the entMeshComponent to the name of the gameTransformAnimatorComponent. In our case, the bindName is TransformAnimator0567 (pictured below).

The gameTransformAnimatorComponent defines how fast the fan spins and on which axis. These settings can be found in the dropdown under animations > gameTransformAnimationDefinition > timeline > items. There, the duration sets the speed (higher numbers means faster), and under impl > axis, you can set which axis it spins on. For example, if the .mesh is parallel to the horizon, you'd want it to spin on the Z axis. The .mesh of the fan in this .ent is oriented vertically though, so it spins on the Y axis.

Another important thing about the gameTransformAnimatorComponent is that it's parented to the entPlaceholderComponent. This is done by setting the bindName of the gameTransformAnimatorComponent to the name of the entPlaceholderComponent. In our case, the bindName is simply entPlaceholderComponent.

The entPlaceholderComponent places your .mesh file including its animation relative to the world origin, or whatever component the entPlaceholderComponent is parented to. This is done via the localTransform within the entPlaceholderComponent. The entPlaceholderComponent doesn't have a localTransform in this specific .ent .

The Actual Tutorial

Adding the fan to the .app

In this case, we'll add a spinning ventilation fan to the hood of a car:

• In the .ent file of the fan from the game files, select all three components that were described earlier, right click them and select "Copy from Array/Buffer".

• Then, inside the .app file of your car, right click the components array of whichever of the car's appearances you want to add the fan to, and select "Paste selection into Array/Buffer".

• Then, inside the entMeshComponent, replace the file path of the vanilla .mesh with the path to the .mesh of the fan on your car.

Blender

The fan is likely fixed in place on the 3D model of your car. Its pivot point needs to be at world origin though, so we need to remove it from its original place and move it to world origin. Its actual position on the car as seen in-game is then set via the localTransform of the entPlaceholderComponent .

• If necessary, separate the fan from its surrounding geometry

• Select your fan in Blender and enter Edit Mode.

• Select the base of the fan, hit Shift + S on your keyboard and select "Cursor to Selected"

• Switch to Object mode, right click your fan and select "Set Origin > Origin to 3D Cursor"

• Open Blender's Sidebar by hitting N on your keyboard and take note of the "Location:" within the "Transform" field of the "Items" panel. It tells you the exact placement of the fan relative to world origin.

• In WolvenKit, copy-paste the X, Y, and Z values into the Position-array of the localTransform within the entPlaceholderComponent

• Then, back in Blender, hover your cursor above the "Location:" field and hit Backspace on your keyboard. This will move the pivot point of the fan to world origin.

• In Object Mode, rotate your fan to align it either horizontally or vertically, depending on the axis perpendicular to its rotation. In this case, we'll orient the fan horizontally.

• Set the Rotation Mode to Quaternion if it isn't already. Blender uses X, Y, Z, W while WolvenKit uses i, j, k, r. It translates as follows:

  • W → r

  • X → i

  • Y → j

  • Z → k

• Copy the X, Y, Z, and W values from Blender into the Orientation-array of the LocalTransform of the entPlaceholderComponent in WolvenKit by following the translation of each axis as described above.

• Since we've rotated the fan into the opposite direction to straighten it, the Orientation needs to be reversed. In our case, the X / i value needs to be negative instead of positive so that it sits at a slight angle on the car.

• Export your fan and import the .glb into your .mesh.

• Change the parentTransform for each of the three new components according to your car if necessary.

• If needed, set the rotational axis of the gameTransformAnimatorCompoent and adjust the duration to taste

• Test in game and see if it works!