View Full Version : Character Roots

02 February 2006, 05:00 PM
This is a pretty general (yet probably highly specific question) about the direction / orientation of the root joint of your characters.

I use Maya (and have used Max previously) and in order to have the ability to control the hips independly of the spine I have the root just above the 'pelvis' of the character (ie the spine goes up form my root and the pelvis goes down one joint before branching out to form the legs)

However, we have recently moved on to applying motion capture to our rigs and it seems that Motion Builder prefers to have the joints going straight up from the pelvis (so the pelvis is the root... and so when rotated, the whole upper body follows)

So my question is this... Have I picked up a bad habit along the way in the drawing of my skeletal structure? And if the answer to this is "No no... you are going about things the right way" then does this adversly affect Motion Builder and give me odd results? (as it seems to right now)

Thanks in advance - sorry for the ramble ;)

02 February 2006, 10:49 PM
I am guessing that motion builder is taking you root joint, and thinking its the pelvis joint yeah? If this is the case, can you not just add in another joint?!?!

02 February 2006, 06:37 AM
The key is the rig.

Motion capture data relies of accurate rigs, and proabably motion builder does too. Where as previous to this you were build animation rigs, controlled by the animator and not motion capture data. So your right in both cases the two are different.

In this the keys is motion builder and how it interporates, motion capture data, a lot of house have custom tool which transform motion capture data onto an animation rig, like the one you first stated. My rigs are like this to, the hip control is in the center so i can move the hips independantly.

Most mocap rigs rely on an standard fk bone heirachy, and some ik. It how this data is handled back on to the rig - so motionbuilder relies on a rig/skeleton more intuned with a mocap skeleton. This makes sence though because this is what motion builder generally uses.

02 February 2006, 04:16 PM
Thanks for the reply guys.

Vyntax - I'm not sure it's quite as simple as that, though I think you have the got to the nub of the problem. I'm still not 100% convinced that the actual direction of the root is important though.

Eek - Thanks for putting my mind at rest a little (at least I know I'm not doing something fundamentally stupid!) I guess you rig for the 'job in hand' so to speak - but I wanted the ability to switch between mocap and control rather than having two seperate rigs; and to achieve that the mocap rig is basically a barebones copy of the control rig (with the mesh on a 3rd barebones rig linked between the two).

I've since played around with this today and I think it is more to do with actual placement of the root (ie I think I'm putting the thing too high) - but I'm still kinda second guessing myself since I am new to MotionBuilder and MoCap, so any more thoughts or info (or random comments hehe) would be welcome :)

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02 February 2006, 04:16 PM
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