binding joints to a robot

# 1 18-02-2007 , 11:21 PM

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how do i bind joints to a robot guy without getting deformation on the balls acting as joints?

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# 2 18-02-2007 , 11:33 PM

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Hello Roger,

you need to use rigid bind and do each moving part seperately, ensuring that the joints are central to the sphere that you are using as a hinge. For example when binding the forearm, select the forearm and elbow geometry then the elbow joint and rigid bind them, then for the shoulder select the upper arm and the shoulder geometry then the shoulder joint and bind them and so on.

I used the forearm and shoulder as they are simple to explain, you should start at the end of each limb then work your way to the torso when rigid binding so in reality you would start with the finger tip and work your way to the shoulder.

Hope that helps you out,

Mat.

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# 3 19-02-2007 , 02:25 AM

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ok, i have it all good and stuff, but i have another question: i want the wrists and ankles to be able to rotate, but when i ik them they cant, but when i dont ik them they cant be used to move the forearm around.

Last edited by roger_squawk; 19-02-2007 at 02:52 AM.

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# 4 19-02-2007 , 03:06 AM

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If you have finger joints then you would need to bind them too, you don't need to do the last joint in the chain as it wouldn't be moving anything. I've attached an image of a hand that I made and rigid bound a while back, hopefully it'll explain a little better than my words. I've marked the geometry and the joint that I'd bind together in the same colours.

Sorry if I confused things,

Mat.

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# 5 19-02-2007 , 10:03 AM

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for not getting deformation in your model i would recommend just parenting all your parts... hand to forearm, forearm to elbow, elbow to upper-arm, upper-arm to main body, etc... and then just using rotates and keying said rotates. this ensures absolutely no deformation in body parts and still moves the lower parts according to how you move the upper parts... most people try to use some sort of rig with bones, but i don't think it's necessary for your method of animating.

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# 6 20-02-2007 , 02:41 AM

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ok. thanks. i think ill stay to bones, because isnt parenting fk?

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# 7 20-02-2007 , 07:48 AM

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yup, it is.

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# 8 21-02-2007 , 09:59 PM

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yeh ok. i prefer ik, but ill keep the parenting idea in mind.

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# 9 23-02-2007 , 02:56 AM

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yes, parenting is fk, and any skin bind will give you deformation.
So what you really would want is a composite rig. that is, create your skeleton, but instead of rigid binding things to it, place the pieces into the skeleton heirachy itself (or parent constraint it). This means that your ik will still work, and nothing deforms (unless its supposed to, and then you bind it). This works at all levels of the heirarchy; although it can get a little tedious to put all the pieces where they're supposed to go.

Oh, and if you don't have them, I reccommend creating controls - just curves that the ik handles are parented to. makes them a little easier to grab and otherwise control.

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# 10 23-02-2007 , 04:09 AM

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Xander-O,

not all skin binding will create deformations, the method that I have illustrated, using rigid bind, produces no deformation.

Here's an example..... CLICK ME

Cheers,

Mat.

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# 11 23-02-2007 , 04:18 PM

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i am still getting deformation. is it because i bound the fingertips to the finger? im confused about this stuff (ive only done modeling before). also, should i revise the skeleton at all? now that i think about it, i need to stick the parent joint in his hips rather than his middle so he can bend down and stuff.

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# 12 23-02-2007 , 11:30 PM

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Hello Roger.

Firstly, the skeleton that you've made looks fine from the front, I can only assume that it's ok around the smaller joints too (hands etc.).

Regarding the deformation that you're getting, I'm not exactly sure which joints that we're looking at in your image but I think that it's the elbow and waist, it looks as though you've bound the limbs above and below the joint.

Using the elbow as an example...

You have bound the upper arm, the elbow sphere and the forearm to the elbow joint on the rig. You only need to bind the elbow sphere and the forearm to your rig. It works in very much the same way as parenting the geometry (as Neostrider sugested), but as it's bound to the skeleton you can use IK also.

Remember, you need to bind each moving part seperately. In the image that I posted previously the red parts were selected and bound, then the blue, then the yellow Note that it's the rig joint, the geometry joint and the geometry that follows the joint that is selected each time. Work your way, in this fashion, through your robot and it'll be fine.

I hope that helps,

Mat.

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binding joints to a robot

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