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markw

COG's

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Sometimes when dissecting and otherwise looking through models I come across a bone named COG in capital letters. But I can find no documentation as to what COG's are.

Are they relics from an earlier time in A:M's history?

Can anyone enlighten me?

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Sometimes when dissecting and otherwise looking through models I come across a bone named COG in capital letters. But I can find no documentation as to what COG's are.

Are they relics from an earlier time in A:M's history?

Can anyone enlighten me?

 

I assume that refers to the "center of gravity" of a rig or an aspect of a rig.

 

I think that I've sen a few rigs that have had nulls or bones with the label "COG" in auto-balance type set-ups etc.

 

The rigger would not have to name it as COG specifically but it is easy to understand the purpose of the bone at a glance when viewing a long list of bones.

 

I believe that Mike Fitz (3DArtz) used to sell a tutorial for using his COG rig years ago but I don't know if that rig had any kind of auto-balance system or not.

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Mike Fitz's COG is another term for fan bones. I think he called it that because it resembled a gear.

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Ah, so it is something left over from A:M's past then.

They also pop up in, for me at any rate, unexpected places. For example here's the Cube Primitive model as shipped with A:M and it too has a COG bone but it has no moving parts?

After some further digging around in the ever interesting Extras DVD, I found a PDF by Mike Fitz entitled "CogRig (PS'3dartz')" unfortunately it's password protected, so it seems its secrets must remain hidden!

Screen_Shot_2013_08_05_at_10.39.18.png

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They also pop up in, for me at any rate, unexpected places. For example here's the Cube Primitive model as shipped with A:M and it too has a COG bone but it has no moving parts?

 

On the primitives Yves made the COG probably does stand for "center of gravity" :rolleyes:

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to the OP,

My COG joint setup cd that I use to sell was a (as Robcat mentioned) setup that I used to animate and control my models.

Its nothing more than an extensive setup of fan bones that handoff / pass along motion to the nearby fan bones of other joints to control the bending and stretching of a models joints.

For example, the cog in the shoulder had its base bones connected to the bones that emulated the top of the rib cage and the bottom of the rib cage would hand off to the stomach and so forth and so on.

 

the pdf that you have in the extras cd does not cover any of the cog setup, it just covers the steps to install a stripped down version of the hash 2001 rig.

I took out the Auto Center of Gravity system as it more handcuff than helper in the rig. I can't really remember for sure what the password is as the server and backup drives I had all that on was flooded away in hurricane sandy... but try "3dartz" in the password field. that should open it.

 

Just for the record I have modified and improved the system since the CD. But other things have kept me from being as busy with A:M as I used to be.

 

If you have any questions about it, let me know

 

Mike Fitz

www.3dartz.com (server is currently offline.)

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Good to have you stop in, Mike!

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Mike's Cog setup is an extremely usable system of fan bones that works well for shoulders, but also for all knuckle, elbow, knee joints, etc. I purchased this from Mike years ago and learning it was a very helpful exercise. There are lots of alternative systems of course, and I *think* Mike's system predates cp weighting, but it's one of many alternative methods for deforming joints in a believable way.

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Mike's Cog setup is an extremely usable system of fan bones that works well for shoulders, but also for all knuckle, elbow, knee joints, etc. I purchased this from Mike years ago and learning it was a very helpful exercise. There are lots of alternative systems of course, and I *think* Mike's system predates cp weighting, but it's one of many alternative methods for deforming joints in a believable way.

 

thanks for the words Gerry. I think cp weighting was a couple years after the cd. But I've never been interested in using cp weighting on model other than for small precise areas. I think using bones is the best way to go for controlling the models joints and body... there are exceptions though.

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Martin argued against adding CP weighting for a while but said he decided to add it when he saw some people were having to use a separate bone for almost every CP to get the gradual deformations they wanted.

 

There's an elephant in one of the old stock collections that has a blizzard of bones in it for that reason.

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Martin argued against adding CP weighting for a while but said he decided to add it when he saw some people were having to use a separate bone for almost every CP to get the gradual deformations they wanted.

 

There's an elephant in one of the old stock collections that has a blizzard of bones in it for that reason.

 

Its my experience that bones offer more control than control point weighting ever could. The one thing I will say about the "cogs" setup I made is that I have not come across any setup that handles every position of the human hips better.

Also, I don't think there is any drawback from a computing standpoint to have a huge number of bones in a model, as opposed to having a huge number

of control point weight "data containers".

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It comes down to a matter of preference and what you're comfortable with. It's just nice to have more than one solution for these things. I often mix-n-match a number of approaches to get where I want to go.

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When I was a boy we didn't have that fancy fan-boning stuff or CP weighting or smartskin... we had to make do with a diagonal spline ring at every joint... and we liked it! th_old.gif

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