To IK or not to IK?

Development Character & Animation
1

I have a skeleton and several animations in Blender that I want to port over to UE4. But I wan to know a few things:

Should my skeleton be IK or FK before exporting? Which does UE4 like more?
Do IK skeletons perform rag-doll physics in a normal manner?
Any quirks that I should know about (besides blenders scaling issues with export, and buggy import of multiple animations)

Currently my skeleton has IK controls for hands and feet within blender using its IK constraints, I want to know if there are any limitations I should know about before throwing my character in.

Thank you for any help :slight_smile:

2

Perhaps I should clarify:

Does Unreal Engine 4 require my rig to be FK on import? What is the intended workflow?
Should I leave my rig as a FK, then use UE4 to create IK chains?

Thanks in advance.

3

For IK stuff, check out the docs at IK Setups | Unreal Engine Documentation maybe that will help, also for exporting check https://docs.unrealengine.com/latest/INT/Engine/Content/FBX/Animations/index.html .

4

Shouldn’t matter as the animations are all baked down anyway. So whatever you like to animate them (as long as they use a weighted skeleton for deformation).

5

Thanks for the responses :slight_smile:

So hierarchy difference doesn’t become problematic, to make IK in Blender you have to disconnect the control bone from the chain, (making hands and feet siblings with the root spine bone). I thought there would be problems since they’re only held together through constraints. Or do the constraints come with it on import to UE4.

Thanks! I’ll give this a though read :slight_smile: I appreciate the help.

6

Hmm, in 3dsmax you just setup the IK constraint and it has a dummy that does the IK and transfers it to the bones. Maybe you could do the same? I guess its a matter of “try it and see”. Theoretically anything with a bone and an associated weighting should work (basically it looks at the weight for each bone per vertex and calculates the end position of the bone. But export/import can be picky.

7

MODO experience:
I have FK and IK(both, I switch between them during process) for legs/arms + complex deformations for some muscles/mechanisms, because it’s just a tools for animation. If I need FK for particular animation - I will use FK, if IK - then IK and so on.
However to avoid any problems with importing in Unreal, I bake animation and export only pure bones without additional data.
In Unreal I recreate IK, because UE4 IK designed to solve other issues and work with baked animation to create nice effect.

8

Interesting…so you’re recreating IK inside UE4 just for “game logic” purpouses if I understand correctly, right?
Means that ( looking at the documentation for the IK hand setup ) the management of the limbs is driven by a constant tracing of the end effector towards its goal ( terrain or a specific object in the scene ).
Just wondering, other cases where the IK setup inside UE4 is needed?

9

Thank you all for your posts :slight_smile:

I understand this now thanks to everyone, I think I know what my work flow will be now.
I’ll animate using IK and bake it to the FK rig, export the FK rig to UE4 and perform any further adjustments for interactivity there (like uneven ground detection per-foot etc.)

Thanks again :slight_smile:

10

This one can probably help. I’ve did it actually, it doen’t work directly with TPP skeleton, but with some adjustments you can make it run

11

Yeah, exactly!
Well, I was thinking about using IK to solve problem with overhang jelly :slight_smile:

However due to new priorities I don’t have time to experiment with it, but just as example of another use case!