Exporting Bones for UE4

[Anonymous]

Hello @all,

currently I am working with a purchased model with built-in bones (as seen in the screenshot). However, the import of this model to UE4 does not work as UE4 says the model has "multiple root bones". As you can see, the bones are integrated into the model.

My question now is: how can I export or at least separate the bones from the model? If this is not possible, let me explain what I want to have in the end.

As you can see in the second screenshot, the model has special parts which should be moving/bending with the parts attached to them some kind of a hosepipe). Can you give me some advice to achieve this?

Thanks in advance

[J450NP13]

Are you sure you don't want to just export the animation?

[Anonymous]

No, it is not a fixed animation. The movement of the hosepipe should be generated automatically, if the parent parts are moving.

[J450NP13]

Last time I checked that's not how that works.  But I haven't worked in the UDK for years.

[Anonymous]

So how can I achieve this in another way?

[J450NP13]

In a game there is only going to be so many different positions that the hose would be in...you will have to animate it into each pose.

Show us what you want it to do.

[Anonymous]

It should just behave like a real hosepipe, if you can imagine that. I thought the built-in engine physics could handle this.

[J450NP13]

So you think that the engine would just take a model and add physics to it automatically...knowing how you want it to react?

A box that you kick...or something falling or breaking is one thing....taking a model that is connected between two other objects and making it react to the positions of those separate objects would take some serious 3D math that would make your head explode.

Is this on a character?

[Anonymous]

Here is a video of what I want to achieve:

https://www.youtube.com/watch?v=PT83a_7IxYw

Do you see the black hosepipe? It bends according to the movement of the attached parts. Thats what I want to achieve and I thought it would be possible with bones, joints or whatever and the built-in physics. The model I use has already those bones defined and I just wanted to know how I can use them in UE4 as they won't be imported properly, with UE4 complaining about multiple root bones.

My question is: is it possible at all to use those defined bones? Or is there a way to just import the model (without bones) and define them in UE4?

[J450NP13]

I haven't worked in UDK for some time...so I don't know if they added any features that would do this...but I would use the bones that are in it now and deform the hose depending on what position the model is in.  Using physics is only going to make your rig more expensive as far as draw calls and functions.  You would have to program the bones to react the way you want...which I am gathering you don't know how to do and could be very pricy for someone else to do.

animate the rig in maya and export it like a regular animation.

[Anonymous]

Thanks for your help.

Maybe someone who has worked with UE4 recently may help me further.

[J450NP13]

I'm telling you by experence that you do not want to use physics to drive the movement of this hose.  It will be overkill to say the least.

That's why the bones are already there to keyframe them with the armatures....

[Anonymous]

Are keyframe animations really an option if I want the robot to move freely in all possible directions? I thought that would be just useful for fixed animation sequences.

[J450NP13]

If you are controlling it then no...you would program it....thats why I asked what it was for and you didn't answer me.

[s_ehrenhaus]

Oy, in UE 4.11  they added a new anim dynamics node. Have a look at this stream.

https://www.youtube.com/watch?v=5h5CvZEBBWo

Not sure if you fixed the multiple root bones issue but you basically need all bones to be under one main bone, no broken/open hierarcheis.

In regards of that animation you want to achieve: Have a splineIk rig in maya. Skin the driving curve to the main machine arm bones so you have the base animation baked. For additional dynamics you could either set an nHair sim in maya. This is better if the machine function arms cant be controlled by the user to create jagged motion that wasnt accounted for within a maya sim.

Otherwise add a chain animDynamic node in UE4 as shown in the video. Or if you work on priveous versions of UE4, you can also use the springBone node which is a somewhat different thing but does similar dynamic behaviors. The big difference between animDynamic and springBone is that animDynamics is relative to the character movement component. So it doesnt react to world transforms. The springBone does, but its slightly less stable and will jitter if you move too fast.