Game Engine Export¶
2 type of rig can be exported: Humanoid, Universal.
Shape keys are exported, all types are supported in Unity and Unreal Engine, and probably other game engines supporting the Fbx format as well.
New bones created in the rig are not exported by default. To export them:
Their name must starts with ‘cc_’ (stands for custom controller, e.g. ‘cc_sword’).
Or tag them with a ‘cc’ or ‘custom_bone’ property, by adding a custom property to the bone
Stretch - Scale¶
Extra stretch/length of the arms and legs is not properly handled by the Fbx format, since the children bones always inherit the scale from their parent bones. Also, it can lead to incorrect bones rotations. For this reason, set to zero the “auto-stretch” and “stretch length” values of the arms and legs, and do not move the “c_stretch” controllers (elbows, knees). Also bone scaling is not supported properly as well. The best approach is to scale bones in Unreal/Unity directly.
In game engines, dual quaternions skinning is generally not supported, unlike Blender does with the “Preserve Volume” feature in the armature modifier. So make sure to uncheck Preserve Volume in the armature modifier in Blender to see the right deformations.
It may be best to use multiple twist bones for the arms and legs, see Arms Options
Animations of shape keys are exported automatically. They are baked for each actions then injected in the Fbx file.
However, shape keys won’t export if there are topology-changing modifiers such as Subsurf in the mesh modifiers stack. If you really need to export these topology changes, consider using this addon to apply modifiers before exporting (modifiers can’t be applied by default with shape keys).
Exporting animations with or without root motion is easy in Unity: the root motion is automatically computed by Unity that is looking for the center of mass, regardless of the bone hierarchy/animated bones nodes. It’s a different matter with Unreal: to make it work, the Blender armature object itself must be animated. Auto-Rig Pro also includes an option to transfer the “c_traj” bone controller animation to the armature object at export time only, to avoid animating the armature object.
By default, the IK feet and hips (“c_root_master.x”) controllers are parented to the “c_traj” bone. Animators may prefer to disable it, so that the “c_traj” controller does not influence other bones. To do that:
Select the IK feet bones (“c_foot_ik”) and set their Child Of constraint influence to 0
Select the “c_root_master.x” bone, enter Edit Mode (Tab key) and clear its parent bone
In Blender, animations are called “actions” and multiple actions can be created for a character. However, when exporting to Fbx, all actions contained in the file are exported by default, no matter if they’ve been created to animate the rig or other objects. Exporting actions that are not linked to the rig may potentially corrupt the character animation. To see why, open the Action window of Blender, and try to link other actions to the character. It may get distorted, scaled weirdly, depending on the keyframes stored in the action.
To fix it, in the export options, you can click the eye button to display the exported actions. In the following example, only “soldier_rigAction” is the right action to export with the rig. So, it’s either possible to delete the other actions by clicking the X button, or check the the Only Containing option, and enter “soldier” in the text field to export only the soldier action.
These tools are useful to identify and fix quickly possible problems with the rig, that would make it not compatible with export, especially bones stretch issues.
The Check Rig buttons only reports issues in a pop-up window, while the Fix Rig button will apply the following changes:
Disable all possible arms and legs stretches (c_stretch controller set to location 0, disable auto-stretch, set stretch length to 0…)
Disable the Preserve Volume option of the armature modifiers of skinned meshes, to show the actual exported deformations in Blender.
This may change somehow the result, then it’s recommended to check that animations still look good in the scene, and you can correct them if necessary.
Universal exports a simplified bone hierarchy for any creature: bipeds, quadrupeds, spiders, centaurs…
Humanoid is for bipeds only. It exports a simplified bones hierarchy like Universal, plus supports the Unreal Mannequin bones orientation as an option and humanoid naming convention. It’s useful for retargetting, root motion… The drawback of this type is the bone restriction: in Unity to setup more facial bones than the jaw and the eyes, extra steps are required.
Ensure the character is not too small, otherwise it may lead to issues, such as bad retargetting. Try to consider one meter = one grid unit, ideally it has to be approximately this big compared to the grid floor (see screenshot below). Scale the mesh and armature (S key otherwise).
Once the character is rigged and skinned, select its armature and go to File > Export > Auto-Rig Pro FBX
Choose the engine to export to (Unity, Unreal).
By default, all skinned objects are exported. To export only the selected ones, click Selection Only.
Custom bones: if you added your own custom bones to the armature, make sure they are named with the ‘cc_’ prefix, thus they will be included in the export. If they are parented to an FK bone, they will be parented to the deforming bone automatically. E.g, if “cc_watch” is parented to “c_forearm_fk”, it will be parented to “forearm_stretch” which is the final deforming bone in the exported armature. If “cc_hat” is parented to “c_head.x”, it will be parented to “head.x”. Make sure to parent them directly to the “_stretch” bones when using an IK chain which has no direct controllers, such as “forearm_stretch”.
Check Advanced if you need to export the bend/secondary bones (especially useful for cartoon characters to curve the arms, legs).
Arms and legs secondary controllers are automatically exported if they’re set to Twist (see Secondary Controllers)
Check Push Additive if secondary controllers are set in Additive mode, to compensate the weight loss of the additive bend bones, since the additive armature is not exported.
Check Export Twist to export the twist bone. When checked, a percentage can be defined to set the amount of twist. Generally 0.5 gives best results.
Enable No Parents to support stretchy animated bones. Caution though: to achieve this, the bones are unparented, the rig hierarchy will be exported broken.
Enable Units x100 to export internally with 0.01 unit scale. This allows retargetting in Unreal and initialized scale transform in Unity as well (1.0).
Bake Actions to export the actions (animations)
Export Baked Actions Only to export only the baked actions.
Check Only Containing and enter a word on the right to export only the actions including this word in their name. E.g. setting “soldier” will export the action “soldier_walk” but won’t export “john_walk”. Useful when dealing with multiple actions in the scene.
A Simplification Factor can be adjusted to lower the file size at the expense of the quality. Lower values are recommended to fix “floating” feet effects when exporting.
A Global Scale can be applied, but this is generally not recommended. Better scale the armature and meshes before exporting.
The Fix Bones Rotation and Fix Bones Matrix feature should get rid of animation issues when exporting (bones weirdly rotated at some frame)
Enable Initialize Fbx Armature Rotation to export the rig with rotation values set to 0 (warning, it’s experimental, does not work with root motion yet)
The bones axes can be changed using the Primary and Secondary parameters
Humanoid covers the same features as Universal plus the following ones. Note that Unity internally handles the wrist twist, so twist bones are not allowed there.
Full Facial exports all facial bones, otherwise only the main ones are exported (jaw, eyes…)
[Unreal Only] Check Rename for UE to rename the bones according to the Unreal Engine’s humanoid naming. Unity will handle the default names properly so this checkbox is not visible when Unity is chosen.
[Unreal Only] Check Mannequin Axes to match the bones orientations with the Unreal Mannequin. This allows to directly import the skeleton as the Mannequin skeleton in Unreal. It requires 4 spine bones. It’s also best to export the character in A-Pose when exporting to UE, see Changing the Rest Pose.
[Unreal Only] Check Root Motion to transfer the “c_traj” bone animation to the armature object animation when exporting, to support root motion in UE
[Unreal Only] Check Add IK Bones to add the Unreal Mannequin IK bones: “ik_foot_root”, “ik_foot_l”,…
Export by Script¶
Here is a little code snippet as example to export a character by script:
import bpy import os # set the file path output here file_output = "F:\\MyExportFbx.fbx" # set some settings... bpy.context.scene.arp_export_rig_type = 'mped' # types: 'humanoid', 'mped' bpy.context.scene.arp_engine_type = 'unreal' # other useful options # bpy.context.scene.arp_keep_bend_bones = True # bpy.context.scene.arp_units_x100 = True # bpy.context.scene.arp_bake_actions = True # bpy.context.scene.arp_export_name_actions = True # bpy.context.scene.arp_export_name_string = "test" # bpy.context.scene.arp_mesh_smooth_type = 'EDGE' # bpy.context.scene.arp_ue_root_motion = True # bpy.context.scene.arp_export_noparent = True # bpy.context.scene.arp_export_twist = True # export it bpy.ops.id.arp_export_fbx_panel(filepath= file_output)
Unreal Engine Tips¶
If the mesh have shape keys, importing with Use TOAs Ref Pose enabled may lead to incorrect blend shapes in Unreal. If this happens, make sure to turn it off.
The Unreal humanoid rig features 4 spine bones (root + 3 spine bones). So it’s possible to set the Auto-Rig Pro spine count to 4 too in the Rig tab of the Auto-Rig Pro panel. Otherwise, when assigning the regtargetted bones, just map the spine_03 slot to the spine_02.
Make sure the ‘advanced’ bones are properly mapped (click Show Advanced to display the facial and fingers bones). If you don’t use them, click the X button to unassign.
For better results, pose your character as the target rig rest pose
To avoid strange arm/legs rotations after retargetting, set their translation type to Skeleton. Display the retargetting options by clicking this in the bones tree:
Then set to Skeleton this property:
Sometime, because of differences in the rest position of the source and target rig, or because the animation itself contains artefacts, it’s necessary to apply rotation offset over the retargetted animation for better results.
It’s especially true for the fingers. Here is how to fix wrong fingers rotations of the ThirdPersonRun included in UE:
Select and rotate the bones in the 3d viewport (animation window)
Select all the bones you’ve modified in the Skeleton Tree:
Click the Key cross button then the Apply button.
Save your asset and you’re done!