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IK Rig of a Mechanical Arm with Individual Constrained Rotations


kalotriqona

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Hey! I've been troubled by this likely small road block for a whole day now so I decided to ask for some help.

Most tutorials on mechanical IK rigs I've seen only show how to create an arm with a 'ball bearing' type of hinge however I need one where the rotation is constrained to one axis on some of the inner hinges and another axis on the other hinges. I think it's best explained by the .c4d project file itself but I'm including a screenshot of a tree as well. Hope that makes it clear!

Cinema_4D_2020-09-09_16-47-25.png

mech_arm_ik.c4d

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Wow, that is intense hehe. 
I opened the file trying to figure out what is supposed to happen, but it wasnt super clear. I can see that there is this rotational hinges in the middle and on the "hand" but are these the only moving parts? or will be the entire thing? 
can you do a quick sketch of what the movement should be? 
 

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10 hours ago, FLima said:

Wow, that is intense hehe. 
I opened the file trying to figure out what is supposed to happen, but it wasnt super clear. I can see that there is this rotational hinges in the middle and on the "hand" but are these the only moving parts? or will be the entire thing? 
can you do a quick sketch of what the movement should be? 
 


Hope this helps!
 

 

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This is not optimal, but I think it might give you some options on how to achieve what you need.
One thing I noted from your file, is that the hierchy on the object manager was reversed. The mounting plate was the very last and the robots "hand" was at the very top, and it should be the other way around if you want to use IK.

The other thing you will note from my file is that I am using a joint structure and binding the mechanical parts to those joints, but not all of them. The ones that are going to be rotated, are placed inside the hierarchy of joints, but they are independent, they dont affect the IK because of their placement.

And usually the controllers for a rig, I leave them outside of the joints, but in this case, the rotational ones, I kept them inside, so when the IK moves, the controllers will follow. There is a much nicer and tidy way to do that, but I didnt have time. Rmeember that for those rotational joints, the PSR has to be checked only for rotation, and not position, neither scale.

 

TesteRobotArm.c4d

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Thanks a lot, I learned a couple things from your rig already. Couple misunderstandings though, the hierarchy was actually correct but I didn't make it clear, sorry about that!
Now in your rig I see and tried the rotation controllers however them being independent they don't rotate the arm as well, only the joint itself rotates. Furthermore I do actually need to move the goal in all axis, which those rotational joint should allow but as you've mentioned there's some wonkiness when moving sideways in this type of IK rig.

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Ah, Im sorry, i thought the hierarchy was inverted! 
Hmm... yeah, I think there is still a possibility in doing what you want from an IK rig, if you place other joints inside the IK controlling joints, so they can follow the movement and position, but you can still make their rotation fully controllable from the outside. 
Unfortunately, I have a delivery today, and cant stop any second 😞
But this weekend, I might have some time, and will give it a proper shot. 

I can actually see already a solution for your mechanical arm, I will try it again this weekend!
 

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On 9/11/2020 at 12:41 PM, FLima said:

Ah, Im sorry, i thought the hierarchy was inverted! 
Hmm... yeah, I think there is still a possibility in doing what you want from an IK rig, if you place other joints inside the IK controlling joints, so they can follow the movement and position, but you can still make their rotation fully controllable from the outside. 
Unfortunately, I have a delivery today, and cant stop any second 😞
But this weekend, I might have some time, and will give it a proper shot. 

I can actually see already a solution for your mechanical arm, I will try it again this weekend!
 

 

Hey Flima! Have you tried the IK rig? Let me know if you need more time.

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