IK definitions_ semi Long

[AdamT]

> 1. what exactly is the role of an effector?
> and what is the difference between a goal and a constraint?

> 2. Are all goals (root goal and tip goal) effectors? seems so from the manual.
> So are effectors goals or are goas just one type of effector?

Effectors and goals are two different things. In IK, an effector is attached to a bone chain and it attempts to reach the goal. So you animate the goal and the effector will follow along. It affects the bone chain insofar as the bone chain follows the effector. So, the effector follows the goal, and the bones follow the effector.

> 3. Do I understand correctly that you use the root goal to animate the position of bone ,
> and the upvector to rotate the bone?

See above regarding the goals/effectors. And yep, the up vector is used to orient a bone in a particular direction. It's most commonly used to keep leg bones from spinning out of control.

> Manual = "upvector constraints let you orient the axis of a bone towards a control object."
> So what does the tip goal do?

Honestly I'm not sure what the difference is between putting a tip effector on a bone vs. putting a root effector on the next bone down the chain.

> 4. What is the rule to determine whcih bones need a root and tip goal (is it every bone). Which of the above constraints /goals do you typically animate?

In IK you only want to animate the goals, so you need a goal for every bone that needs independent movement. For a typical leg rig you would have an effector at the end of the shin bone, an effector at the ball of the foot, and an effector at the end of the toe. I normally group all of these effectors under a null and then animate the null for general movement. Then you can separately animate the toe and foot goals to achieve foot roll.

> 5. Its been said often " softIK is not the best solution all the time". I thought softIK was pretty much the old IK with new constraints /calculations. to prevent dead spaces (whatever that is).

It is that, but it's also a sort of dynamic system. Because SIK is calculating some movement on its own, you give up a certain amount of control. Sometimes that's a good thing, e.g., it will give you secondary motion without having to keyframe everything, and sometimes it's a bad thing, e.g., you don't always want exactly what SIK gives you.

So there's my non-expert 2 cents. hth

[bcbarnes]

Here's a go at answering some of your questions as I understand them (which is also somewhat incomplete):

1. An "effector" is a "dummy" object placed at the tip of a bone or limb and is a child of that bone or limb. This "dummy" can then be given a "root goal" to allow you to move the tip of the parent object.

I spent a long time with the MOCCA manual trying to understand tip goals until I realized something: You see, there really aren't "tip goals". There are only root goal and up vectors. To create a "tip goal", you actually create a dummy object as a child of the object that you want to control, and position that dummy object at the tip of its parent. Then, you can create a "root goal" on the dummy object. Now - moving this root goal moves the dummy object, which in effect moves the tip of the parent object (in IK setups). Add a TIP goal, and notice that it has in fact created a new dummy object, and put a ROOT goal on it in the attributes manager.


2. Effectors are the "dummy" objects I talked about in #1. Goals are different. There are root goals, and up vector goals, and by the use of effectors, you can "fake" tip goals. See #1 above.

3. Root goals animate the position of a bone/limb, up vectors control where the bone/limbs "Y" axis points (i.e. it controls rotation around the "Z" axis) (this is configurable in the AM). Tip goals (root goals on an effector) control where the Z axis of the bone/limb points (i.e. rotates around the "X" and "Y" axis).

4. Tip goals go on bones/limbs when you want to be able to point the tip of the chain at something. This would be like maybe the head of a snake or something. Root goals go on things you want to actually move - such as a foot bone or hand bone. Typically, on human characters anyway, I've used no tip goals at all, root goals on the toe and foot, and root goals on the hands. This allows me to move the foot (through the foot root goal), and control its up/down angle (through the toe root goal) while keeping the toes pointing forward.

5. SoftIK is only one animation means. There is also normal IK, and FK. Fingers are often done with straight FK because of the extra control you get. With normal IK and SoftIK, you have less direct control, but then you have to fiddle with less joints too.

As for which ones are C4D specific, beats me. I haven't used any other apps except MotionBuilder, and while that app talks about IK and FK, and it uses the term "effectors" for the joints that you can control with the IK/FK rig, it has its own rigs and you don't really create goals or effectors, so I'm not sure if it's the same thing.

Hope this helps, and that I'm not TOO far off base.

[Zoogie]

Adam,
Thanks , this is exactly the kind of simplified explanation I am looking for , I will digest it and see if I come up with any more questions.


It helps a whole lot.,
:bounce:

Zoogie

[Wilson-3d]

Hi. It has been a few months and I don't have time to check the docks but I will tell you what I can remember.

You can make the null (effector) object a shape and size. Make sure and set up the orientation under the object tab in the Attributes manger. This way you can make it encompass say the foot and click on the null (effector) object. The Effector will be the goal for bones. They will point toward the effector. So once the rig is set up you have certain bones that have the effector as a goal. In teh end you could say raise the effector that surrounds the right foot and the foot raises and the knee bends. The goals tell the bones where to point and constraints only let the bone rotate a specified amount.

Basically goals are effectors. They are both null objects. Just that a goal is an effector(null) that has been specified as a goal for a bone.

An up vector keeps your bone rotated in that basic direction. So say the upvector for the knee is in front of the knee. Now when you raise the effector-goal that surrounds the foot the upvector helps the knee bend toward the front as a knee would adn not bend backward like it is broken. This happens in cg animation and is known as gimble lock. When you raise the foot and the knee bends the wronge way. This is a large part of what upvectors do.

I usually use a root and tip goal.

Have you gone through the mime tutorial? things will get more clear from repition.

I hope that helps I have to get back to work. I noticed others have replied since I started tyoing but I may as well post now that I have typed this much:wavey:

[Zoogie]

Thanks fellas I feel like I can finally begin to learn this thing. With all your help. I should have asked this sooner. Maybe I wouldnt have struggled so much.

I notice I posted at the exact same time you did BCbarnes, Hence I didnt get to read that post before my previous post.
I also notice you are in Austin., I am in Houston. Maybe, one day when I am in your area we can get together..

Thanks again.
Zoogie

[That Adrian Guy]

:beer: :beer: two for Adam and one for me! :beer:

[bcbarnes]

Zoogie - Gotta love texas!

I actually live up in Round Rock, which is about 30 miles north of Austin, but who ever heard of "Round Rock"...

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