Advanced RIG and Animation - Stretch and Squash

Hello everyone ! I’m actually doing some RIG and Animations stuff for an unannounced game.

I actually trying to improve my skill and workflow. I’ve seen lot’s of AAA Game footage, making of and GDC vidéo and i actually want to try to make some Rig that can use some Stretch and Squash feature in view to improve some mouvement !

This is what i want to try =

Well … Ok, it’s blizzard, and the rigging job seem to be trully perfect, but i’ll want to try to make some basic rigging stuff that can simulate some stuff like this.

In view to do this, i’m asking if i can use Scale on bones in view to import this in UE4. I’ve heard scalling bones can give many issues and it’s absotly not a thing to do but i’m not sure about this !

The bones scalling can create some good squash stuff like a Canon muzzle scalling up when shooting, or maybe some more complexe mecanical stuff like reactor etc…

If someone know if BoneScale can be easily import into UE4 without issues or if someone have some good tips about Rigging/animations tip for making some effect can look like Stretch and squash !

Thanks all

Hey man, I use bone scale in my stuff a lot. Stretchy limbs, spine, I also have a few helper bones that use their scale to fake large muscle movement like peces, lats and stuff around the belly. Also for things like volume management on areas like butts or breasts its pretty useful to have the scale channel at your disposal. I have worked with some complex animations involving all sorts of skeletal hierarchies and bone scaling and to this date found only one small problem involving the .segmentScaleCompensate attribute for joints in maya. You have to have that on on all bones in your hierarchy or it will mess up your animation when importing to UE4. Not quite sure what goes wrong there, but I guess UE4 bones are more simplified than maya bones. It doesnt store information like joint orient or things like that. So if you import an animation with bone scaling and child segmentScaleCompensation turned off UE4 will mess things up according to the conversion maths.

One other issue I found is that UE4 exporter DOESNT export the scale information (at least in 4.10, I pray to the gods they fixed that or planned to do so)
So if you have an animation in UE4 and want to get that back out as .fbx (maybe a retarget from an other skeleton or for whatever reason) it wont have the scale animations in it. Thats not a very big deal, but it sure sucks for the few occasions where getting stuff out of ue4 is needed.

Anyway, tl.dr. yes you can use bone scales in ue4.

You can use the Transform Bone in the AnimBP of your character and expose that value using a float, so that you can later access by casting onto that character, but the downside of the Transform Bone node is that it scale the joint and its children, so if you scale ( for example ) a hand it will also scale the fingers.

Not sure if this setup can be changed to affect only one joint rather then its entire down hierarchy, possibly by coding.

Ok !!! Well, nice news ! I was pretty sur BonesScalling was a bad thing to do … Have to try all this stuff now =) Thanks for the answers !