Pole Vector Causing Rotations On Joint Chain

[sz200]

I need some help with Pole Vectors. I've setup a FK/IK switch arm and I am trying to add in the Pole Vector on the IK arm now that I have finished it. What I have noticed is as soon as I throw the PV in, it causes rotations on my shoulder and forearm joints, along with the arm moving slightly.

Here are the before and afters on the shoulder joint rotations:

BEFORE AFTER

Here is the layout of the joint chain in case it helps......

FRONT

TOP

Any ideas or help as to what am I doing wrong? Is this always expected and is there anyway I can position that Pole Vector to the 'magic' spot where it wont cause rotations on any joints? Thanks.

[tirumalaimuttu-shanmugam]

create polygon tool is a better option.
keep three points(vertex) on joints using point snap tool to form a triangle.
select the middle point(ie the vertex in the elbow joint) n go to move tool options n change the move settings to normal.
now move the u coordiante far away to extend the plane.now make the surface live n snap ur control on the extended plane. do polevector constraint now.u r joints wont change its orientation.hope this ll help u......

[sz200]

QUOTE(tirumalai @ 04/13/07, 12:49 AM) [snapback]264009[/snapback]
create polygon tool is a better option.
keep three points(vertex) on joints using point snap tool to form a triangle.
select the middle point(ie the vertex in the elbow joint) n go to move tool options n change the move settings to normal.
now move the u coordiante far away to extend the plane.now make the surface live n snap ur control on the extended plane. do polevector constraint now.u r joints wont change its orientation.hope this ll help u......

Huh??? What does create polygon tool have to do with pole vector constraint. You got me all confused...

Are you saying make a flat plane with the create polygon tool and snap that to the elbow, to use for the pole vector? How would that fix the problem of rotation issues. There is no difference whether you use a piece of geometry or a curve as the pole vector object.

[joojaa]

Well,

theres some truuth to the idea. Wehn you make the triangle you create a plane at wich the pole vector should lie after you switch back. Offourse you could probably do a mel scrit that does this instead but otherwise its sane.

THis saidits one of those things you often think you want to do but dont. See its nt a good solution to have a fk ik switcher that is on and then off. Why? Well the heart of the matter in animation is ithe time derivates. and now if you just switch over your not going to have any controll of the way the transitional speeds match eachother.

So if you instead animate the ik and then the fk and blend in the solution it does not matter much. As long as you can capture the correct ik position offcourse.

[sz200]

QUOTE(Joojaa @ 04/13/07, 06:46 AM) [snapback]264029[/snapback]
Well,

theres some truuth to the idea. Wehn you make the triangle you create a plane at wich the pole vector should lie after you switch back. Offourse you could probably do a mel scrit that does this instead but otherwise its sane.
THis saidits one of those things you often think you want to do but dont. See its nt a good solution to have a fk ik switcher that is on and then off. Why? Well the heart of the matter in animation is ithe time derivates. and now if you just switch over your not going to have any controll of the way the transitional speeds match eachother.

So if you instead animate the ik and then the fk and blend in the solution it does not matter much. As long as you can capture the correct ik position offcourse.

This is nice and all.. but could anyone clarify or help me with the pole vector problem? Because from reading the 2 above posts I am not understanding what I should be doing to fix the problem.

[tirumalaimuttu-shanmugam]

QUOTE(sz200 @ 04/12/07, 11:32 PM) [snapback]264018[/snapback]
Huh??? What does create polygon tool have to do with pole vector constraint. You got me all confused...

Are you saying make a flat plane with the create polygon tool and snap that to the elbow, to use for the pole vector? How would that fix the problem of rotation issues. There is no difference whether you use a piece of geometry or a curve as the pole vector object.

i m not asking u 2 use the flat plane as pole vector. i m asking u to create a plane similar as RP of the IK n extend it then snap ur pole vector ctrl over the plane to get a non rotation value of the sholder bone.

[joojaa]

Oh by the way before you continue be sure you set the prefeered angle for the bone in any other state than straight.

[sz200]

QUOTE(tirumalai @ 04/18/07, 06:15 AM) [snapback]264312[/snapback]
i m not asking u 2 use the flat plane as pole vector. i m asking u to create a plane similar as RP of the IK n extend it then snap ur pole vector ctrl over the plane to get a non rotation value of the sholder bone.

Sorry I don't quite understand.

I wound up just creating the pole vector by playing trial and error with the pole vector controls placement until I got some rotation values on the shoulder that were as close to 0 as possible.

If you could simplify what you suggested so that I understand it a little better, that would be great... otherwise, thanks for at least trying.

[telene]

I think I understand what Tirumalai was originally saying:

In order to ensure your joints keep their 0, 0, 0 rotations, you need to essentially make a "guide" that will create an exact coordinate where your pole vector shape needs to be placed.

Here's how:

Use the "Create Polygon Tool" to create a triangular polygon using the joints in your arm (or leg, depending on what limb you're making a pole vector for. I'll use the example of an arm here.). Create the poly by ctrl+V snapping to each of the 3 joints in your arm that comprise the IK handle (eg. Shoulder, Elbow, Wrist).

Go into component mode to see the vertices of this new polygon. The easiest way (imho) to do so is R-clicking on the poly and selecting "Vertex" from the menu that pops up. Now, select only the vertex that lies in the middle joint (ie. the Elbow).

Use the move tool, but first in Tool Settings, switch move settings to "Normal".

Now, move the vertex along it's normal in whatever direction (horizontal) pulls the vertex naturally "away" from the joints. See an example here. Once the vertex is moved to the location you want your pole vector shape to be, go back into object mode.

You can either make the object live (as Tirumalai suggested), or, while having the triangle selected, choose to show it's vertices. Do so under Display > Polygon Components > Vertices

Now, you can take whatever object you plan on using for your pole vector (I use a nurbs cone), and just ctrl+V snap it to the vertex you moved. (See pic)

Simply create your pole vector as you normally would now, et voila! No unwanted joint rotations.

Hope that helped.

Of course, the best way to prevent joints rotating incorrectly while creating a Pole Vector is to ensure that your arm/leg joints are in an absolutely straight line (flat plane) in the Front orthographic view (See pic). However, if somehow that gets messed up, the above solution will work.

And, of course, don't forget that from the Side orthographic view (for the leg), and Top orthographic view (for the arm), there has to be a noticable "bend" in the joints so the IK handle will know which way to make the elbow/knee bend.