Beer glass scene creation
This course contains a little bit of everything with modeling, UVing, texturing and dynamics in Maya, as well as compositing multilayered EXR's in Photoshop.
# 1 22-09-2011 , 06:31 AM
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Quad Hind leg rigging = grr for beginners

Hey guys, I'm gonna give a little backdrop to my issue to get the best response possible, so I apologize in advance if I seem a little long-winded. I'm basically a beginner, or rather I used to animate with maya many years ago (2003). I left the 3D game (heh, see what I did there?) for awhile, and now I've found myself suddenly back into it, helping with a big indie game project, armed to the teeth with... outdated, obsolete, VERY rusty knowledge. The short version... I'm a beginner again. :O

So rigging. I've been assigned to rig a quadruped. The only thing I remember about rigging these guys is keeping in mind it's like a human leg but standing on the tippy toes. I'm gonna be honest, there's not a lot of free info out there when it comes to specifics. I've been following this tutorial here https://www.peachpit.com/articles/art...02262&seqNum=3 but it seems a little outdated and my rig doesn't seem to be achieving the same results it's intending to give me. I can't seem to find any better ones for the moment. I think the only way I can describe my multiple issues is to put it in pictures... and again I apologize for my newniness. user added image

So here's the rig. From what I gather my issues seem to stem from the joint orientation... but I'm not quite sure:
user added image

I'm at the point where I'm to orient constrain the IK controller at the top of the shin, to the bottom ankle joint. I'm guessing this is to give rotational control over the foot. But I then this happens:
user added image
What I notice is that the Y axis is facing forward when it should be up. After the orient constrain, the axis for the foot joint follows suit. I get that, but what I don't get is, why was the the Y axis in the upper shin not facing up like I had it do when I first oriented all the joints when i completed building the skeleton?

So there was that. I decided to trudge on, keeping that problem in mind and hoping maybe an epiphany would hit me. Besides, it seems without that constrain, I can bend the leg relatively normal, and perhaps I could build a separate control for the foot later. However if I pull the leg up to a certain level (like say a pose where the cat is sitting, this happens:
user added image

Okay, well the next step is to add a pole vector. So I create a pole vector and follow the instructions on the tut. Oops!:
user added image

But wait! Everything seems to be aiming at this pole vector, so what if I move it to the front like I would a biped?:
user added image
You are Eka!

... not really...
user added image

But, wait, what if I parent the pole vector to the IK?:
user added image

Boom? Iunno man, it just seems to me like it's there's gonna be chaos when it comes to animatin' time. I mean I still have to add controls to the foot, but I only seem to have sideways rotation, but not up and down.

Oh and I can't seem to zero out the IK handles, freezing transformations just makes them go weird.

Constructive thoughts please. user added image

# 2 22-09-2011 , 09:43 AM
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Join Date: Feb 2003
Location: UK
Posts: 6,287
Kaiem

no answers yet??? Jeez!!

I dont think its too big a problem to be honest. Looking at the images, your IK is in the wrong place. You have it placed from the 'hip joint' to what is known as or what would be the 'hock' on this type of leg. You need to have it start at the hip and end on the ankle. You cant freeze the the transforms either on an IK handle, it just doesnt work. To control the knee you have to place either a locator or a control curve of your making at the back of the front leg (its elbow), and at the front of the knees on the back legs - our knees point forward not backward, then simply select it and the IK handle and hit pole vector, job done! Also make sure for this joint set up that you have selected the IK RPSOLVER.

As a note, you can group the knee control to itself, rename it and parent it to say the root node, this way the knee control will move along with the rest of the rig when you animate. Then is just a case for you to place a controler to move the leg around


Also I notice the leg joints are linked to a single joint coming down from the back bone, I would take them off of that single joint and create another joint per leg either side and connect them up that way, almost like a pelvis. You'll most likely have better control over the rig. Also check your joint placement as the knee joint on the front leg looks too high above 3 edge loops where the actual knee is on the model, also check the back leg too, the joints look too shallow in their placements to the mesh

Ive done a small diagram for you. Hope it helps, I think I drew the elbow pole vector ctrol at the front on the front legs - ignore that and place them behind, at essentially the IK handle 'runs' at the front of the legs from the hip to the ankle

Jay

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# 3 22-09-2011 , 03:22 PM
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Awesome, I'll try those things out. Meantime I've found another tut to follow, guess we'll see how this one goes.

Thanks a bunch!

# 4 23-09-2011 , 04:14 AM
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k so follow up to this problem. Once I add the pole vector, this happens:
user added image

I checked my orientation and everything seem to be right. The only way I can get it to be normal with the pole vector in the position it is is by turning the IK's twist to 180. Which I'm pretty sure no good will come of that.
user added image

But it matters little due to the fact that it's still not behaving like a leg. user added image
user added image

Am I missing something in that knee joint?

# 5 23-09-2011 , 07:43 AM
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Lead Modeler - Framestore
Join Date: Feb 2003
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Posts: 6,287
did you set preferred angle on the knee joint before adding the ikhandle?

J

# 6 23-09-2011 , 01:56 PM
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Lead Modeler - Framestore
Join Date: Feb 2003
Location: UK
Posts: 6,287
mmm, I have no idea what you are doing your end, so out of the goodness of my darkest soul I have done you a quick movie that I hope you can follow as it works for me when I do it.

https://outlaws3d.com/OutlawsImages/LegSetup.avi right click 'save target as' it should work

anyone else can feel free to download it, I'll leave it there for for a bit then it will be gone as I dont want my server being bashed LOL

cheers
Jay

# 7 23-09-2011 , 03:34 PM
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Oh wow. Sorry to make your darkest soul just a smidge brighter but you are my hero. lol
Huh. The tut made it seem so much more complex than that.
but I figured out the problem with the wonky bending, I didn't have the knee joint far enough forward so the IK was crossing over it before it even moved. So now what should I parent the pole vector to so it moves with the model? Does it matter?

# 8 23-09-2011 , 05:04 PM
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Lead Modeler - Framestore
Join Date: Feb 2003
Location: UK
Posts: 6,287
no you dont parent pole vectors. You parent the knee control. Group the knee control or locator to itself and parent the group node on the rig somewhere you can get to it like the root node

J

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