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[SOLVED]Questions: Third Person Rig, what do these extra bones do?

So I downloaded the .zip of the ThirdPerson FBX https://wiki.unrealengine.com/File:ThirdPerson_FBX.zip
I’m looking at the rig, and I have some questions.

  1. What’s with the Twist bones for the thigh/calf and arms; which don’t control anything and nothing is rigged to? Why are these there if they don’t influence anything?

  2. Foot and Hand IK roots, then child bones for “L” and “R” IK of each, (I know what IK is, but again they don’t seem to influence anything, do these have a purpose or use case in a TP shooter?)

  3. Toe is called “ball”?

  4. IK gun bone? What is this, and should I make one for my character (making a TP shooter) and how are these use in UE4?

  5. Should feet bones be perfectly parallel to the ground for proper in-game IK placement? Does this even matter?

I’m no stranger to rigging, but apparently there’s something I missed because I see a lot of extra bones with curious placement, and I want to know what functional purpose these have for games, and if should I include these things in my rig.

Thank you to anyone who can answer any questions :slight_smile:

1: Twist bones would normally influence the upper portion of the thigh and forearms. This is a quick sample video:https://www.youtube.com/watch?v=0H5DIDZcGVU
It makes things look better. It may just not be influencing anything in the sample mesh you’re working with but a real character would have upper thigh, upper arm, lower forearm, and lower shins rigged to the corresponding twist bones. That’s how I’ve done it at least.

2: I’m not entirely sure what the IK thing does since it’s not really documented but I ended up finding a use for them myself. I think I only remember seeing these in the UT3 models that came with UDK and haven’t seen them recently in UE4. I actually took them out in my UE4 game since I found better ways to do this with the anim event graph.

I was setting the positions of the IK control bones to some world position using some skeletal control that sets their absolute transform. Then the hands would try to IK to the transform of those bones if that makes sense. In UE4 I just get the transform directly from code in the anim graph and find basically no use for these IK bones.

If anyone else has a better explanation I’d be interested in hearing it.

3: Toe is called ball because it’s the ball of the foot. Heh, yeah… I think it’s actually not the toe but the part right before the toe which is the ball of the foot.

4: IK Gun Bone might be an offset from the hand where to actually place the gun relative to the hand. I think this is what you’re talking about?

5: Not sure I completely understand the question. I think they need to be in whatever placement you want them to be relative to the ground. When the foot IK kicks in it should move the feet to the right height so they stand properly on stairs. And then I think you want to rotate them to align with the slope. Whatever pose they are in will be preserved but rotated and repositioned relative to the ground if you set it up right.

I’ve seen in assassins creed for example, the character starts posing the foot a little differently to make it look more like its standing on tip toes. That probably takes extra code if it happens automatically somehow.

  1. Put out your left or right arm palm down. Wave bye bye. Now focusing on your hand “try” to rotate “only” the hand to the palm up position. Can’t be done with out the full rotation migrating up the full length of the arm up to the shoulder. The twist is there to offset the rotation progression starting with the hand as part of the IK solution. With out the twist your wrist will crush.

  2. In general they don’t do anything in engine ( by default) until you wire something to them with purpose in mind. The Mixamo package for example has no IK effectors.

  3. Legacy. Have yet to meet a rigger that did not have their preferred naming convention.

  4. It’s just a bone by any other name and a better name would have been AUX-gun. When animating for prop use is handy for doing simple stuff like changing a knife from one hand to the other.

  5. Bit fuzzy. If by setting your rig and zero out the transform then no it’s not a good idea to set your IK rotation at 90 degree angles as to world space. If setting up an IK chain the solution wants a preferred angle upon creation and if the chain is 90 from hip to toe then you can run into a bad case of gimble lock or the chain pulling into the opposite direction.

Thanks for the answers guys! I understand now, you’ve both been immensely helpful :slight_smile:

These questions only came up because I was ready to export my character’s rig into UE4 for the first time, but I wanted to look at the sample character that ships with UE4 first just to make sure I constructed my rig right for games, looking over their set-up is what produced these questions.

Sorry my 5th question wasn’t very clear, but you guys managed to give me the answer I was looking for anyway. :slight_smile:

Thanks again!