Rusty IK skills!!

[BuzzLightyear]

 

 

It’s been ages since I needed an IK skeleton for a figure, and clearly I’ve forgotten the procedure.  I need to articulate the legs separately as usual, but also want the knees to bend automatically when the pelvis is pushed down while the feet are planted on on the ground.  Think of a simple pelvis, with two legs and feet for arguments sake, with bone order starting from the thigh down to the toes.  It’s simple to add and IK handle between the heels and hips, and the toes and heels to control them.  But the only way I can get the feet to remain planted while pushing downward on the pelvis is to reverse the bone order (i.e. starting at the toes and going up to the hip).  But I clearly remember there’s a way to do this in the normal top-down bone configuration.  An explanation of the setup would be appreciated.

 

Also, I don’t actually need a reverse foot setup, but it would be useful to know.  I’ve looked online and found several setup examples for Maya, 3DS, etc..  But I don’t believe they are applicable as shown when using EI (different procedure for bones and constraints).  But if anyone has a clear example of a reverse foot as well, that would be appreciated.  (I thought there was an example on the EI website of a full IK skeleton and reverse foot, but can’t seem to find them now.)

 

Many thanks for any input :-)

[AVTPro]

Hi Buzz, 

I have two tutorial DVDs that show how to rig characters with simple IK legs and feet as you are requesting. The DVD's sell one for $85 and both for $125. They are immediately downloadable and will serve for a great reference if you ever have a long stint without rigging. Also, I am a freelance and fix the problem or rig in a hour or so if you need.  I use paypal for the DVDs or services. I am glad to help and I can make a quick sample file if need be. 

To answer your question. There shouldn't be a problem especially if you don't need reverse foot but I can rig that too. 

1. Make effector box for pelvis
2. Make two bone chain for upper and lower legs. Joint end is ankle. stop. 
3. Select joint end. Add IK. 
4. Make effector box for foot. 
5. Parent Upper leg bone to Pelvis and IK to foot controller. Done. 

It's best to make to make a separate bone chain for the foot with an IK and parent it in to the foot null or Ankle joint end. Sometimes I forget when I haven't rigged in a while too so I have to look at my DVDs. ;-) 

[BuzzLightyear]

Hi AVT-

 

Thanks for your prompt reply :-)  I was sort of doing what you described, but tried your exact instructions as well.  But I keep getting a circular link at the last step, which was my original problem.  Here’s what I did:

 

1)  Pelvis Box Null created

2)  Thigh and calf bone created - stop.

3)  IK handle between calf joint end (ankle rotation location) and thigh.  No problem, IK works fine.

4)  Created single bone in foot from ankle to toe, added IK.  (I only need to point the toe, not bend ball of foot.  So I didn’t add a second bone at the ball of the foot.)

5)  Parented Foot bone to Joint End of calf (ankle rotation location).

6)  Parented Thigh bone to Pelvis Box - no problems.

 

Result:  As expected, IK works fine when moving ankle; knee bends and foot moves with ankle IK handle.  (However, foot does not remain level as it does when inverting the bone chain.  My goal is to have the knees flex when I depress the  Pelvis, and the foot remains level and stationary on the ground plane.)

 

However, I can’t create another IK handle between the upper leg bone (Thigh) and foot bone due to a circular link (from calf to thigh).  So when I move the Pelvis, the entire leg chain moves and the foot doesn’t remain on the ground, flexing the knee automatically.  Does that make sense?  

 

I’ve done this years ago, and it was really simple.  As you described, it’s just a matter of linking the parts correctly, and everything works.  

 

Question:  Did I misunderstand your last instruction?

 

5.  Parent Upper leg bone to Pelvis and IK to foot controller.  

 

Does that mean “Parent upper leg bone to Pelvis” and “add IK between Pelvis and foot bone”? 

 

- Or - 

 

“Parent upper leg bone to Pelvis” and “add IK between upper leg bone and foot bone”? 

 

Both result in a circular link, as expected due to the IK handle in (3) above.  So I think I’m still not quite getting it…

 

[BuzzLightyear]

Hi again ATV-

 

I think I’ve got it now, thanks.  I actually got it to work with an inverted IK chain, but it’s a bit limiting in some ways.  I’ll play some more with it, but your “normal” direction chain should work just fine.  Thanks for pointing me in the right direction - sorry for the confusion in my last posting.  It’s been ages since I played with IK bones!  ;-)

 

Buzz

[AVTPro]

Should be exactly like this. I think where you are going off is on 3. Add IK to end joint. I think you are adding it "between".  Just select the "joint end" and add IK. It will add the IK to "two bones", not one. Don't select any bones.  I actually did it earlier before I wrote it.  Sorry I didn't back sooner.  You shouldn't have to invert anything. That would be backwards and not how a rig is generally handled. 

I attached a project. 

Depending on how stable or immobile you want the foot to be while moving the pelvis, just switch the parenting from "Joint end/ankle" to foot effector/ctrl. 

I do all kind of rigs, all kinds of ways, but a reverse foot rig isn't necessary stabilizing the foot. EIAS rigging very sufficient for most jobs. It just depends on how you like animating. Here I parented the foot bone 1 to the Joint End so the foot can move with the pelvis. That means the foot will move slightly when the knee bends. That's normal. However if I didn't want the foot to move at all when the knee bends, I would parent it to the foot effector. 

I go over a lot of this in the DVDs. Check them out if you get a chance. Thanks. 

AVTPro_RR_Leg91.prj.zip

[BuzzLightyear]

MOST appreciated AVT!

 

Yes, I  definitely wasn’t getting it, because I was trying to build a rig with a _single_ connected chain.  It never occurred to me to keep the foot completely separate from the upper leg, and then select three effectors to move the whole foot, and upper leg IK handle at once.  Trying to build it with everything connected was my problem.  (I was clearly looking at human anatomy a little too literally, and not considering the flexibility of bones.)

 

Thanks for the insight.  I added a Global Mover to your example, and will re-create your rig and re-animate my character today :-)

 

Buzz

[AVTPro]

I'm not exactly sure what you mean by "three effectors". I only have two in the sample project and image. Maybe you added another for the toe, which you mentioned earlier?

Anyhow, glad it worked out fine for you. And yes, you can't exactly translate human musco-skeletal,  biomechanics kinesiology too literally into CGI rigging. ;-)  My DVDs are full of finger biting, hair saving, mind numbing tips. ;-) Rigging can be tricky to learn on your own. 

Stay tuned for a really sophisticated rigging animation David Wu and I did for Daniel Lee's Exhibit in Taiwan. 

BTW, I started this robot today i Zbrush. I'm trying to do robots in a day. This took about 8 hours...I think it could be quicker. Happy Rigging in EIAS. Enjoy!

[BuzzLightyear]

Wow AVT!

 

Your “Bot in a Day” is super!  He looks amazing, and especially for a one day(!) effort.  I know zip about Zbrush, and have to model “the old fashioned way” ;-)  My Bots take immeasurably longer, and I’ll try and attach a image of them.  But for some reason, I’ve never been successful in attaching files to my posts, and sometimes have to have Tomas upload them for me.  I can’t figure out why they won’t attach - I’m using Safari like most Mac-Heads do.  I copy and paste the image, and it appears fine.  But when I log in and look at the posing, it's gone!  (The attached Bots were Modeled in EI Modeler, Maya or MacRhino.)

 

 

And thanks again for your IK help.  The rig works great, and I’m going to fully rig the rest of the character today.  He’ll be a combination of bones and deformers, and it should work out great.

 

Thanks for the robot teaser - he’s excellent!!

 

Buzz

 

Yup... I posted it and the pasted image disappeared.  Never could figure out why...

Edited February 4, 2016 by BuzzLightyear
Pasted images don't appear! Where's the "attach file" option? The "Insert Other Media" doesn't seem to work for me either. It doesn't give me the option to search for a file on my desktop (?)

[AVTPro]

Yes, don't paste the image. Paste a link to the image file, or use the "Choose file". 

Thanks. Yes, I use ZBrush because it's more like using a paint brush and that's what I'm use to.

It use to take me a long time the older way of pulling points and polys. I'm free from polys now, per se. ;-)