Basics - How to import a Mixamo animation in UE4
The following are basic and generic instructions to correctly import an animation from the Mixamo website into an Unreal Engine 4 project. Playing with the options in Mixamo and Unreal Engine 4, more advanced workflows are possible.
- in the Mixamo website, select the same exact Character you imported in your UE4 project (IMPORTANT - Mixamo fits the animations over the selected character, so it's important to select the correct character first)
select the animation you want to download. The preview will update showing the animation applied to the selected character.
- press the Download button
- in the Download Settings dialog, set:
- Format to FBX Binary;
- Skin to Without Skin.
- press the Download button and download the FBX file;
- import in Unreal Engine 4 the downloaded FBX file (you can drag & drop the file in the Content Browser, or use the Add/Import > Import to option);
- in the FBX Import Options dialog:
- use the Default settings, if in doubt press the Reset To Default button;
- set the Skeleton option to the skeleton asset of the matching Mixamo character (IMPORTANT - this we'll associate the animation to the specified character skeleton);
- press the Import or Import All button.
Done :) You'll find the Mixamo animation in the Content Browser.
Now you are ready to retarget this Mixamo animation to character using the UE4 Mannequin.
Import failed. Mesh contains root bone as root but animation doesn't contain the root track.
If the skeleton of your Mixamo character has been already processed by the plugin, when you later import a new associated Mixamo animation you'll probably get the following error message:
FBXImport: Error: Mesh contains root bone as root but animation doesn't contain the root track. Import failed.
The is a known behavior/limitation of the UE4 Editor: when importing an animation, it fails if the bones hierarchy is not equal to the one of the specified skeleton. When applied, the plugin modifies the skeleton and all the connected animations and skeletal meshes stored in the project, adding the root bone to them. This causes this sort of issue.
While the suggestion is to import both the character and its animations before applying the plugin to the skeleton, you can follow the below instructions to workaround the above issue.
- Ensure to import in the project, in a dedicated folder, a brand new version of the Mixamo character skeleton. The simplest way to do it is to simply make a new import of the Mixamo FBX file of your Mixamo Character, following the documentation;
- following the documentation, import the animation, setting the Skeleton option to skeleton imported in Step 1;
- Save all the imported assets (IMPORTANT otherwise Step 5 will fail)
- Run the "Retarget Mixamo Skeleton Asset" action on the imported skeleton, following the documentation
- When asked, select the "UE4 Mannequin" in the UI (the imported animation from Step 2 will be updated accordingly)
- Right click on the imported skeleton from Step 1, and run the "Retarget to another skeleton" action
Select your original Mixamo character's skeleton when asked (NOT the one imported in Step 1), and press the Retarget button
Done :) Now the new Mixamo animation can be used with your original Mixamo character's skeleton and you can delete all the other imported files from Step 1 (including the imported skeleton).