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View Full Version : AIM Constrain Vs IK/FK


Shady3D
08-21-2008, 01:09 PM
i was watching some rigging tutorials and i thought of a way i think its better for animating than the usual IK FK, it takes the both's advantages.

let me explain, the reason we use IK is because its easy to position the controls but it moves in strait line and the reason we use FK because it makes nice rotational transition between frames or makes arc while moving.

so i was thinking of using an "Aim Constrain". what i mean with this that we make the regular joints then when adding controls, make the cube cc (control curve) at the knee an make an aim constrain between the cube cc and the hip joint.

so if u want to lift the knee u just click on the cube cc then position it then if u made some keyframe and animate and then to see better let the knee joint make a motion curve then play u will find a nice arc done this way, also to control any joint make the cc on the next joint and aim constrain it.

i didn't figure out a good way of parenting and making the hierarchy yet, but that's not the issue i want to know if its really efficient or worth trying or it was a bad idea and i should stick with the regular IK FK controls, so give me ur opinion.

That's an image with aim constrain.
http://www.azoree.com/images/store40/a1882b871f.jpg

and that's another image after number of frames.
http://www.azoree.com/images/store40/b7566e6d0f.jpg

isoparmB
08-22-2008, 02:20 AM
It's not a bad idea. But test it out for rotation flipping. Skin a simple mesh (can even be a cylinder shaped around the joints), to see if there is any pinching when you hit certain poses.

colruno
08-22-2008, 04:58 AM
I looked at it for awhile but don't really see the difference between what that is and IK. I guess with the cube cc curve at the knee your just kinda controlling the end of the bone instead of rotating from the root joint. But its still rotating from the root joint in the end. I see potential in it if you could control both parts of the IK chain from the one box. I.E. moving the box around controls the bone above it, rotating the box controls the bone below it. Then you would only have to select and key the box. Not sure if it makes it any easier to animate though which would be the purpose of any rig.

scroll-lock
08-22-2008, 07:38 AM
I always like people who look outside the box :)
But some questions to think about:
1.What happens when you move the root joint ?
- if there are no properly set up vectors , etc... there will be flipping issues I think
2. What if I want to plant the foot somewhere where I want it and I move the root joint , hips or whatever ?
- Is it staying still , like in an IK solution or there is a slight movement ;)

Shady3D
08-22-2008, 08:02 AM
thx isoparmB, and about the flipping i think there is no flipping as long as u move other cubes cc in the right pose, u can try this on your own and tell me.

and colruno, the point in making this setup is to simply like positioning the angle of a line.

first the joint in Maya is simply a ball (Ball1) and connected to another ball (Ball2) so i thought of why don't we move Ball2 to pose the joint instead of rotating the connection and the pivot will be from Ball1, but that's not good because if we move Ball2 it will increase the scale of the connections and it will be stretchy and that's why we use aim constrain, we can make a box then by moving it its like moving the other ball but with no stretching.

and as i said first posing the cube is easier than posing with rotation, so is it easier to position the cube on the table and make him sit on his knees or rotate it till it get to the pose u want, give it a try and tell me.

thx scroll-lock, i am thinking of what u are saying and try to figure out a way, but i am really not that good in rigging and how to's yet, i am still learning rigging and trying to understand the hierarchy and how each joint affect the other.

Chinwagon
08-22-2008, 01:58 PM
Do you mean something like this?
http://forums.cgsociety.org/showthread.php?f=54&t=521963
It worked pretty well as you had two controls for both IK and FK but I found that posing in FK and making smooth FK arcs was trickier than using straight FK rotations.
:)

Shady3D
08-22-2008, 08:50 PM
WOW i saw the video ur amazing, i was thinking of something like this but what about taking this one step further and make the controls translate in a arc shape, i mean what if we made a hip joint and a knee joint and make IF condition to the cc (control curve) that checks if the distance between the hip joint and the knee is the same so the box will only move in a sphere and its pivot will be the hip joint.

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08-22-2008, 08:50 PM
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