Starting to Bone

[bubba]

I have finished roughing out the bottom portion of my BattleMech and now I want to start adding bones. I believe I should start in the middle portion of the "lower body." Should the "root" bone be perpendicular from a line drawn between the centers of rotation for the two legs? Do I need to add another bone pointing down? From the first (or root) bone I believe that I should draw bones out to the leg joints. Then down each leg, then through the foot pedestal and out to each "claw." All bones should be children of the previous bone - except of course the two in the pelvic region.

 

Here is my model.

 

legs0.tga

 

 

Thanks.

[robcat2075]

A lot of this depends on what "rig" you are installing. For the moment I'll presume you are rolling your own.

 

I have finished roughing out the bottom portion of my BattleMech and now I want to start adding bones. I believe I should start in the middle portion of the "lower body." Should the "root" bone be perpendicular from a line drawn between the centers of rotation for the two legs?

 

I like it that way. In your case i think that's best. Make it a horizontal bone with the roll handle pointing up so +x will be "up" and -x will be "down".

 

 

Do I need to add another bone pointing down? From the first (or root) bone I believe that I should draw bones out to the leg joints. Then down each leg, then through the foot pedestal and out to each "claw."

I recall in some programs a "child" bone MUST be connected to its parent. In A:M that is not necessary, it only needs to appear as a child in the hierarchy as shown in the PWS.

 

 

 

 

 

All bones should be children of the previous bone - except of course the two in the pelvic region.

 

Watch my "Simplest IK Leg" video for a quick explanation of why heirarchy isn't that simple and why you dont' want it to be that simple. It's in the screencam link in my sig.

 

Holmes has some videos that explain these sort of rigging ideas in greater depth.

[bubba]

This is my rigging. I did roll my own. All the parts of the model are separate. The only thing holding them together is the bones. Is there more I have to - constraints etc. - to make sure my model holds together?

 

 

Thanks.

[robcat2075]

Are the claws on the feet really supposed to be animatable?

[robcat2075]

Presuming those claws don't animate, that they move with the feet as a solid unit, then they don't need bones in them. Just attach their CPs to the same bone the foot is attached to.

[bubba]

Are the claws on the feet really supposed to be animatable?

 

Presumably the do - sort of like chicken feet. But at my stage of expertise, maybe I should just deal with the obvious and leave the nuances alone.

[robcat2075]

If they do animate, then they need bones. You can put them in now and choose to not animate them at the beginning.

 

Generally then I'd say your placement of the bones looks appropriate

 

 

If any bones are part of a Kinematic constraint chain, like in my video, any child bone needs to have "attach to parent" ON, for example where the lower leg bone meets the upper leg bone ( a knee).

[bubba]

If any bones are part of a Kinematic constraint chain, like in my video, any child bone needs to have "attach to parent" ON, for example where the lower leg bone meets the upper leg bone ( a knee).

 

Is the Kinematic chain done in the bone mode or in the choreography?

 

Is there a "trick" to finding an "unattached CP" because I seem to have one (or more) somewhere in the model.

[bubba]

What is the difference between "child of" and "attach to parent" for a bone?

[robcat2075]

A child is any bone lower in the hierarchy physically attached or not.

 

 

 

"Attached to parent" (it's a property of the bone) needs to be ON for IK solving and Kinematic constraints to work their way up a chain.

 

An upper leg bone (a thigh) is usually NOT "attached to parent" since you don't want your moving of the leg bones to move the hip.

 

likewise, toes are rarely "attached to parent"

 

 

If a bone isn't positioned to be physically attached to a parent, A:M will move the origin so that it is if you turn" Attached to parent" ON

 

You may want to more carefully place your bones so that A:M isn't doing that for you.

[robcat2075]

I'll also add that only one child can be "attached" to a parent, even if several are physically placed as if they are.

 

If a hand bone has five finger bones that are children of it, only one can have the"attached to Parent" property ON.

 

In the case of fingers, it is most likely that the rigger would choose to have none of them set to ON, even though one of them could be.

[Meowx]

A note; by default, bones should attach to their parent as long as you click near the end of the previous one. For example:

AnimationMasterScreenSnapz001.mov

Here, I have some created some simple mech leg geometry. When I switch to bone mode, I add bones by hitting the "A" key. By clicking and dragging near the end of the previous bone, the new one is automatically attached to its parent. Afterwards, I can switch to a new perspective and align the bones as needed.

[bubba]

Thank you. That was very instructive.