Question regarding importing Mixamo animations


I’m using Mixamo as an example here, but this question is really a lot more general than that.

Mixamo lets you choose to export most animations “in-place”. This effectively eliminates root motion translations in the X and Z planes. This is fine for most cases - for example in a walk animation, we still expect the hips to move up and down a bit. But for jumping, falling, prone, and many other cases, we typically need to lock down the translation in Y as well.

Doing this in Blender (or Maya, or MilkShape, etc.) is possible, but repetitive, tedious, and somewhat error-prone. It would be really awesome if our AssetImporter had the ability to cancel root motions on given major axes, and preferable, for some specific Named Bone / subroot node (such as Hips).

How do you guys deal with eliminating unwanted root motions in animations? What do you recommend?



You can follow that, create your own workflow that you feel comfortable with, then script it out with Python. I don’t see why the engine should be responsible for cleaning up arcane workflow steps when any DCC tool does the job.



Hey, thanks for the reply!

Python (or MEL) scripting does sound like a reasonable way to fly - I’ll definitely look into it. For a handful of animations, that sounds quite reasonable. One problem I foresee is that my animation count is growing exponentially with the number of unique characters, and so it’s likely that I will at some point turn my attention to extending the AssetImporter console application, which is highly suited to batched execution :wink:



You can run Blender from the command line and auto-execute your scripts. You can also use Blender as a module:

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Here’s the list of animations for just the player character - of course we expect the list to be larger for the player than for non player characters, and this is far, far from complete…
<<?xml version=“1.0”>

<Comment> Name of character root node (for manipulation purposes) </Comment>
<RootNode Name="Adjustment" />

<Comment> Names of character's animations </Comment>
<Descriptor Name="Models/PatientZero/Idle.ani"           Looping="true"  LayerID="0"> IDLE                    </Descriptor>
<Descriptor Name="Models/PatientZero/WalkForward.ani"    Looping="true"  LayerID="0"> WALK FORWARDS           </Descriptor>
<Descriptor Name="Models/PatientZero/WalkBackwards.ani"  Looping="true"  LayerID="0"> WALK BACKWARDS          </Descriptor>
<Descriptor Name="Models/PatientZero/WalkLeft.ani"       Looping="true"  LayerID="0"> WALK LEFT               </Descriptor>
<Descriptor Name="Models/PatientZero/WalkRight.ani"      Looping="true"  LayerID="0"> WALK RIGHT              </Descriptor>
<Descriptor Name="Models/PatientZero/Jump.ani"           Looping="true"  LayerID="0"> JUMPING                 </Descriptor>
<Descriptor Name="Models/PatientZero/Falling.ani"        Looping="true"  LayerID="0"> FALLING                 </Descriptor>
<Descriptor Name="Models/PatientZero/CrouchIdle.ani"     Looping="true"  LayerID="0"> CROUCHED IDLE           </Descriptor>
<Descriptor Name="Models/PatientZero/CrouchForward.ani"  Looping="true"  LayerID="0"> CROUCHED WALK FORWARDS  </Descriptor>
<Descriptor Name="Models/PatientZero/CrouchBackward.ani" Looping="true"  LayerID="0"> CROUCHED WALK BACKWARDS </Descriptor>
<Descriptor Name="Models/PatientZero/CrouchLeft.ani"     Looping="true"  LayerID="0"> CROUCHED WALK LEFT      </Descriptor>
<Descriptor Name="Models/PatientZero/CrouchRight.ani"    Looping="true"  LayerID="0"> CROUCHED WALK RIGHT     </Descriptor>
<Descriptor Name="Models/PatientZero/CrouchJump.ani"     Looping="true"  LayerID="0"> CROUCHED JUMPING        </Descriptor>
<Descriptor Name="Models/PatientZero/MeleeAttack.ani"    Looping="false" LayerID="0"> CROWBAR OF DEATH        </Descriptor>
<Descriptor Name="Models/PatientZero/PickupItem.ani"     Looping="false" LayerID="0"> PICK THAT SHIT UP       </Descriptor>

<Comment> Names of bones for Foot-IK </Comment>
<Bone Name="Left Foot"  Value="LeftFoot" />
<Bone Name="Right Foot" Value="RightFoot" />
<Bone Name="Pelvis"     Value="Hips" />

<Comment> TODO: Add ragdoll physics descriptors here </Comment>


I’m not sure I want to execute Blender that many times for every game character, when it comes time to polish. But I guess I could live with it. The assimp-based AssetImporter app is a lot smaller, and loads and runs a lot faster (no graphic interface). It’s still looking like the better candidate for batching stuff, but I’m lazy, and doing it “your way” is certainly less work for me :slight_smile:



May I ask where you get your animations from? Some kind of (free/commercial?) mocap-library? Or are you capturing even on your own?



My question was general, but I used as an example :wink:
The animations could have come from anywhere that Assimp can support.



Basically, I want to eliminate root motion in the Y axis during a Jump animation - the reason is that I use a Dynamic Character Controller, so I expect translation in Y to come from the character’s outer physics hull, and not from the animation in question.

I fired up Blender, and tried removing the keyframes on the “Y Translation” of the “Hips”.
In Blender, the result was what I wanted, so I exported the animation to FBX, and imported the fbx into Urho (via AssetImporter app). The resulting jump animation appeared to freeze half way through playback - apparently just deleting all the keys in some channel, and so the channel itself, leads to corrupt assets.

I then tried dealing with this problem in code - at the beginning of a Jump, I note the local translation of the hips in Y axis, and during a Jump, I force the local translation of the hips to that value, effectively eliminating the unwanted root motion - it works.
I’m beginning to feel that eliminating unwanted root motions in code is more flexible than editing the assets themselves…