Move Pole Vector Without Moving Joint Chain?

[onemoretime]

Ok, I have seen a lot of explanations of how to make a pole vector to some object, but they are pretty thick to me.

Also, I really don't need to MOVE the pole vector, ever. I am making some arms and if I can set it right I can get all the range of motion that I need, but I can't figure out how that works. Every time I touch it the joint chain moves around and it drives me crazy. Is there some simple way to deal with this?

[gmask]

my guess is that you local rotation axis aren't aligned with the world space so the immediate result of making the pole vector contraint "flips out" when you assign it.

Normally if you have and arm you'd want the pole vector locator to be behind the shoulder or if it's a knee you'd want it in front of it

if you don't need a constraint then you can sometimes get away with typing 1 or -1 into one of the x y or z vectors

[gmask]

but to explain further the rotation plane solver looks through a 2d plane for it's solution and then pole vector adjusts the angle that plane is at.

So if you will imagine that you have placed your arm flat on a table.. the pole vector can be on one of the edges of that table and tilts the table but you are still can only slide around on the table top.

the reason you need a pole vector usually for character is because it may work fine when you walk you character forward but if the character tries to turn around his elbows or knees will flip because that plane of rotation is still orientated to the world space instead of the local space of the characters rig. The constraint allows you to connect the pole vecotr tot he local space.. otehrwise it's stuck in world space.

[onemoretime]

Ok, I think I understand already how the solver works (sort of, after a lot of reading and thinking).

But, maybe I am using wrong terminology. I mean the default pole vector that comes with the IK. I have not tried to constrain it yet, but I have been wonding how it decides to put it where it puts it and how to change that. My rigging needs are sort of simple and I am using the IK more as handles than real IK.

So, I will have on the upper arm for example, one shoulder joint, a bicep joint that only rotates in x that's just for making skinning easier on me since I am a novice, and then elbow. Then I make chain from shoulder to elbow and I get a pole vector automatically that points backwards. But what I really want in my special case is for it to point into the body towards the hip. Since it's not real IK I theoretically should not have to really move it around ever because I am only doing one joint on it anyway.

So is my only way to change this using a constraint? If so, I will read up more but I was hoping to avoid this because it seems to be very confusing in its setup. Probably easy once you have done it and know how, but it seems I spend a huge amount of time figuring out some of this seemingly trivial stuff.

Also, is the 'set preferred angle' something to do with this? Since my joints are all in an exact line I don't know how setting the preferred angle would affect this. That is, the shoulder, bicep, and elbow.

Thanks for your help so far. Maybe I am more clear now.

Oh, and maybe I should go into what I am trying to achieve in general. Maybe it's just misguided. I don't really need real IK, I guess. I am just doing game animations and they are not very long or complex so I'd mostly rather use FK. But, I find actually rotating the joints to be super tedious. So, I am using the IK chains of basically two joints (sometimes with nonmobile ones between. That way I can just drag around controls instead of doing rotationg. Plus, I plan to do some aim constraints as well. I guess an odd rig, but that seems to be the style that feels natural to me. I have played with real IK rigs but they seem a bit unnatural and I seem to also get odd results as well. Probably for spine I will do something more standard, though.

I was also thinking I might use spline IK and that would be simpler. Like a spline IK that has just two points for each joint. I am not sure how it works, though, and I am planning to do this for a game engine so I am not too clear on whether spline IK is going to come through the export process unmolested so if possible I'd like to use this (admittedly goofy) method as well. I am happy with it so far, except this one issue needs to be resolved.

[gmask]

QUOTE(arandomguy @ 05/20/09, 08:15 PM) [snapback]308088[/snapback]
So is my only way to change this using a constraint?

nope.. I wasn't clear enough before but if you select the handle you'll notice three entries for Pole Vector. Try entering values or 1 or -1 into one of them until you get what you want.

QUOTE(arandomguy @ 05/20/09, 08:15 PM) [snapback]308088[/snapback]
Also, is the 'set preferred angle' something to do with this? Since my joints are all in an exact line I don't know how setting the preferred angle would affect this. That is, the shoulder, bicep, and elbow.

in order for the solver to know which way you want a knee or elbow to bend you have to have a slight bend and this is either set by default when you create the chain or when you use set preferred angle to tell it which way you want it to bend.

QUOTE
So, I will have on the upper arm for example, one shoulder joint, a bicep joint that only rotates in x that's just for making skinning easier on me since I am a novice, and then elbow.

There are times when you might actually need to do something like this (like making a reverse foot) but basically you are using the ik solver to accomplish forward kinematics when you only need to select the joints and rotate them to where you want them. This doesn't really have any effect on skinning. The joints will have the same effect wether they are driven with forward or inverse kinematics.

But if that's what feels right then that's fine.. there can be some issues with it because the joint may not always reach the handle and can cause snapping in the motion.. the other reason why you should use rotation is that arms and such will have a sweeping motion whereas if you keyframe a handle goign from point a to point b it may end up straight and linear and unnatural.

[onemoretime]

Hmm, it seems when I try that it always moves the joint. My ultimate solution was to go to SC IK instead. That seems to behave how I expect it to. The roboticness is not an issue because I just use two joint chains (well, three joints but one doesn't bend). I can do it with rotation alone but it is extremely tedious because I can't really make it move to the direction I want directly and sometimes it just acts weird.

The extra joints do help deformation. They basically are for twisting. I use an expression to make them partially follow the twist of the wrist and that makes it so that the deformation comes out better.

I guess this is very odd setup but it seems to be what works best for me. I have tried normal IK rig and it's nice for moving the hips but otherwise it just gets bad results for me and doesn't work like I expect, and when I try to use FK rotation it's very tedious.