View Full Version : Moving hip without affecting upper body?
10 October 2006, 11:33 AM
Is there a way in motionbuilder to rotate the hips without rotating the upper body with it. I need this to create the character walk without fighting the upper body. This is using keyframes, not mo cap.
10 October 2006, 11:19 AM
in Motionbuilder under character controls you can pin (the field called Effector Pinnig, pin both: T&R) the spine effector or all effectors above the hip effector. That will do what you want to achieve.
10 October 2006, 01:00 PM
Cheers, but is there a way doing it wthout pining, like making the hip bone point in the other direction, ie, instead of pointing up it points down, giving the pivot point at the begginging of the spine bones, hence rotating the hip will not move the upper body.
Thanks, I guess I need to get use to Motionbuilder a bit, all the best
10 October 2006, 03:08 PM
I don't know exactly what you want to achieve. But I guess what you are after needs to make changes in your rig. A couple of possibilites I see in customizing your rig in Motionbuilder. You could create aux pivots or aux effectors. You can create those by right clicking on the visiual repräsentations of the effectors in the character control window.
But maybe the problem is more fundamental. So that your skeleton layout needs a modification.
Here is a quote from "Inspired 3D Advanced Rigging And Deformations" by Clark, Hood and Harkins:
"Before you parent your legs to the root, there are a few ways to hook up the legs and spine to the root of the character. Each one has a different effect, but the end result is the same: separation of the upper body from the lower body.
• The first way is to just parent the spine and legs directly to the root. By default, this does not let you rotate the pelvis separate from the spine; you have to counter-animate the spine against the root for this to work. ...
•The second way is to duplicate the root to make a hip joint that will be a child of the root and be the parents of the leg. This lets you rotate the hips without affecting the spine, but the root still affects the overall pose of the character and its spine.
•The third way is to add one more spine base joint, again duplicating the root joint and making this new joint the parent of the spine. This might be a bit of overkill, but it helps your spine and leg joints from having to counter-rotate and avoid gimbal lock on root node" (page 81)
Up to now I haven't tried the second and third way but it seems interesting to me.
You also might check the following thread it deals with a very interesting way of a reverse foot set up in MB. I tried it and it works. Maybe you can transfer some of the ideas by "Headless" to the solution of your problem.
Hope that helps
10 October 2006, 02:26 AM
Thanks allot mate, helped. Doesn't seem to be lots of activity in the MB section of CGtalk, so many thanks for being nice and replying and making an effort.
All the best mate!
10 October 2006, 09:49 AM
I'm currently setting up a character that has to have the hips and upper body rotation constrained so that the upper body can be animated separately from the legs. The way I'm currently doing this is to use a relations constraint to connect the rotation of the hips and spine effector to the rotation values of a marker. By varying the weight of the constraint you can hold the control rig effectors in the orientation you want but give them a little freedom to be driven by the mocap/keyed animation so you don't get that completely locked in place 'dalek' effect.
10 October 2006, 09:49 AM
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