I need help with constraining 2 hands to a rake

[Jeetman]

Hello,

 

I need to create an animation of a Winkie raking grass. What's the best way to constrain a long handle (the rake) to both of the characters hands? If I constrain the handle bone to only one of the hand bones, It works fine for that hand. Which means the other hand has to be manually placed. This causes me to have to line up and create a lot of keys to make the other hand appear to be holding on to the rake. If I try to constrain the other hand (to hold the handle) to the same bone or a child bone of the rake, I get a drifted attachment to both hand bones making it impossible to work with. I think it's because the contraints of each hand are compensating for each other.

 

I need a rig setup that attaches both hands to the handle so all I need to do is move the handle and maybe tweak the rotation a little. What would be the best way to do this and should I use IK or FK?

 

I drew a quick picture illustrating what I'm trying to do. Because My computer crashed and I haven't gotten around to installing my paint program, I had to use PC Paint LOL so please excuse the crudeness of the drawing.

 

Thanks,

George

 

[heyvern]

Put two bones in the rake as children of the "main" rake bone. Now just use a constraint on each hand, one for each bone. The extra bones in the rake just needs to be a child of the main rake bone. I would use two bones so they can be moved if you want the "raker" to adjust his grip.

 

EDIT: You could just constrain both hands to the one rake bone... just use an offset for each constraint so the hands aren't in the same place. I prefer the two extra bone method because it's easier to animate.

 

-vern

[robcat2075]

I recommend Vern's plan B. Constrain both hands (IK hands) to the rake and animate the rake.

 

It's much the same situation as this animation where a character has two hands on a shovel:

 

http://www.brilliantisland.com/am/dig25.mov

[Jeetman]

Thanks for replying

 

I think I know what I was doing wrong. I had the arm is FK instead of IK. I'll try it again tonight only in IK.

 

I've been using the "translate to" and the "orient like" constraints. Is this OK to do or should I only use the "translate to"?

 

 

Thanks again for the help!

[robcat2075]

Thanks for replying

 

I think I know what I was doing wrong. I had the arm is FK instead of IK. I'll try it again tonight only in IK.

 

I've been using the "translate to" and the "orient like" constraints. Is this OK to do or should I only use the "translate to"?

 

 

Thanks again for the help!

 

YOu need both translate and orient so the hands maintain their orientation relative to the rake.

[heyvern]

Question:

 

Robcat, why would you prefer the "one rake bone" constraint, rather than having two extra bones in the rake? One bone would be simpler of course but the added benefit of just sliding the bones in the rake seems... easier than offsetting the hands (if you need to that is).

 

Just curious.

 

-vern

[robcat2075]

Robcat, why would you prefer the "one rake bone" constraint, rather than having two extra bones in the rake? One bone would be simpler of course but the added benefit of just sliding the bones in the rake seems... easier than offsetting the hands (if you need to that is).

 

Just curious.

 

your way:

 

place two bones on rake at intended position for hands

pose hands at intended position near bones

press offset button

constrain one hand

press offset button

constrain other hand

 

you still need offset constraints because the bones in the rake will never exactly match the hand bone you are constraining to it.

 

my way:

 

pose hands at intended position on rake

press offest button

constrain one hand

press offset button

constrain other hand

 

If you need to shift the hand position later, offsets are animateable like anything else.

 

 

in both cases you animate the arms by leading them around with the rake.

 

I see both methods as functionally the same.

 

If the rake were never to touch the ground and just be held inthe air by the character I'd do one FK arm , constrain the rake to that, and make the other arm IK, and constrain it to the rake.

 

But if the rake has to be moved along the ground I'd go with two IK arms constrained to the rake

[heyvern]

AHA!

 

The light bulb goes off over Vern's bald head!

 

I forgot about the "animate the hand bones" part. You can just grab those bones and animate them directly. You don't have to type in offset values right?

 

Makes sense. Thanks for clearing that up.

 

-vern