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largento

Fun with Fan Bones

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Darkwing asked about fan bones, and especially difficulty rigging shoulders.

 

I'm by no means a rigging expert, but I thought this might be a fun topic just to demonstrate simple rigging stuff.

 

One of the tricky aspects of the shoulder is that when your arm rotates, you don't want your shoulder to rotate. You can use extra bones with constraints to gradually lessen the movement of the mesh.

 

Typically, fan bones are used to lessen the angle of a bone's movement (making the cosmetic bones fan out, hence the name), but they can also be used for roll contstraints.

 

For example, here's a tube with each bone controlling a spline ring. When I rotate the bone at the end of the chain, it twists like this:

 

Screen_shot_2011_08_23_at_3.05.47_PM.png

 

If however, I add fan bones and set constrains so that each of them rotates a percentage of the bone at the end of the chain, it twists like this:

 

Screen_shot_2011_08_23_at_3.06.08_PM.png

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Interesting, I must learn more! Cause I know my body model is modeled fairly well with the splinage being quite clean and smooth, so this must obviously be where my problems lie

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CP weighting has mostly made fan bones unnecessary.

 

Here's the classic use of fan bones:

 

You have a tube with two bones and a joint and bend it and this happens:

 

Screen_shot_2011_08_24_at_12.16.13_AM.png

 

Fan bones can be set up for every spline ring and set with an orient like constraint. These are set to percentages of enforcement (in this case, the center spline ring has 50% enforcement and the next ring has 90% enforcement):

 

Screen_shot_2011_08_24_at_12.15.16_AM.png

 

The same thing can be accomplished by changing the CP weights of the spline rings (the center spline ring's weighting is 50/50 between the two bones and the next is 10/90):

 

Screen_shot_2011_08_24_at_12.17.24_AM.png

 

The results are pretty similar

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So how does one go about using CP weighting? I remember that's how it used to be done in my old Anim8or days, but the system was pretty...archaic then with that program

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So how does one go about using CP weighting? I remember that's how it used to be done in my old Anim8or days, but the system was pretty...archaic then with that program

 

 

Quite simple, DW!

Grab some CP's... right clik in the yellow box that encircles the grabbed CP's... and a menu will appear- select 'Edit CP weights'. The dialogue is quite intuitive, the crux of it being that you can assign multiple bones by percentage to multiple or singular CPs.

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Really?! That's it? Amazing! I shall have to experiment later today when I have the chance!

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Really?! That's it? Amazing! I shall have to experiment later today when I have the chance!

 

Yup. TAoA:M definitely needs an update. I'm not sure CP weighting is mentioned in it.

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No, I don't think so, I think the best we get is the Auto Assign Bones with the ol 2001 rig on Thom

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No, I don't think so, I think the best we get is the Auto Assign Bones with the ol 2001 rig on Thom

 

Dont forget the bone fall-off and so on... here are nice things available... so I still dont understand where the hype about CP-weights comes from... that is really something totally ordinary available in most packages... SmartSkins on the other hand are really powerful if used in the right way...

 

See you

*Fuchur*

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There are TechTalk vidoes on weighting, bone falloff only, if I recall correctly.

 

[EDIT] It goes over both the bone falloff and the weighting dialogue.

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I had difficulty finding out info when I first started using A:M. I think the first time I actually saw CP weighting being demonstrated was in one of ItsJustMe's video tutorials. Then I bought Will Sutton's CDs. You can see it online for free now on his YouTube account (Zandoria.) It's specifically about weighting and smart-skinning a realistic shoulder.

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The info is certainly out there, but I'll want to make sure it gets introduced in NewTAoA:M

 

The Eggbot's knee is a case that requires CP weighting so that will be an opportunity is nowhere else.

 

 

Has CP weighting only been around since v10?

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The info is certainly out there, but I'll want to make sure it gets introduced in NewTAoA:M

 

I think that would be great.

 

I remember there were a few things that were big "aha!" things for me. One of them was seeing CP Weighting done.

 

[EDIT]

 

Thinking about this reminded me of those Wannabe Tutorials (comic-book-style) that I did a couple of years ago. A lot of those were intended to cover those "aha!" things. Sad now that I stopped doing them, but I do remember that the very first comic book style tutorial I did was about CP Weighting and it can be found here. Not to toot my own horn, but if you are just starting out with modeling, be sure and check out those tutorials. They contain a lot of the things that I wish someone had told me when I first started trying to model!

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If I find the time, I kind of want to take a stab at doing a series of video tutorials on prepping rotos, modeling a face and texturing it with one of the Red Squad characters I'm in the process of building, mainly because of that. I still kinda consider myself a newb (despite the fact I'm on my 6th year of using AM) and I think I still sorta think how a newb thinks when they approach AM :P

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Holmes' face rigging tutorial was what opened my eyes to cp weighting and I highly recommend it.

 

Chris, one further note on cp weighting that should be mentioned, is that you can lasso-select the cp's, BUT if you select them by clicking one-by-one, in the cp weighting dialog box, the cp's will be listed in the exact order you clicked them.

 

Also, note that if you select cp's with a hook between them, the hook will show up in the list as a "phantom" cp. that can get confusing if you don't know about it.

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