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Thread: problems with rig / animation

  1. #1
    Lightwaver dines's Avatar
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    problems with rig / animation

    I followed the board for a while now and it was great usefull and full of inspiration... this is one of my first posts so bear with me...

    I did some research on rigging and set up my first character.
    I put it into poses... and I thought it would work quite well.

    Then I started to do a walkcycle and on changing step the knee kind of jumping and jittering...

    Is this because I missed something in my setup or is it because I am doing something wrong with animating...

    help would be great... attached I am sending my LW scene file for better explaination...

    - dines -
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  2. #2
    Someone fixed something like this a while back. Thry a search on the forum with some key words.

    Edit: Here's the one I wasa thinking of:

    http://vbulletin.newtek.com/showthre...ght=walk+cycle
    Last edited by Surrealist.; 07-29-2005 at 02:03 PM.

  3. #3
    Lightwaver dines's Avatar
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    thanks for the quick response and thank you for finding the link because I couldn't ...

    I read the thread and find out that most of the advices are about prebending limbs. That is what I already did...

    What I also figured out is that the scene of the thread starter snaps in pitch direction... in my scene the knees jump, jitter, snap (whatever) in heading...

    dines

  4. #4
    My Guess is going to be your rest bank rotation is giving your rig the problem. It ideally should be at 0. Not familiar with how you have it all set up but the solution is to go back to the rest position (frame 0 or wherever you have it) and deactivate then rotate the leg bone bank to 0. You'll then need to adjust the other bones to get them back where they were. (deactivate first of course) You can do this with the aid of cloning the object and using those bones as a reference. Then reset with r each bone you have changed.

    You should actually go though your entire rig and correct this. It has to do with which viewport you created the skellegons.

    Also the other problem might be the rest position of the heading. It should not be above 90 degrees. This can cause gimbal lock. IK is getting confused. Either way same basic problem. Try to get all your bones as close to 0 as possible for their rest positions but definately under 90 degrees.
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  5. #5
    Lightwaver dines's Avatar
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    Hi Surrealist thanks for taking the time to look at my rig.
    Yes the rotation... I am trying to fix that. By using the reference you mean this technik which is also discibed in Timothy Albee's book...?

    I did not use Skelegons though, I tried to take advantage of the "new cool" setup tools coming with lightwave 8.
    but when I drag the bones with Joint move they get some sort of rotation ... and I wasn't aware of this.
    Can I ask you some basic questions which were bothering me and I could'nt find a descent answer.
    These rotation bones (bones in z direction on certain joints) some use them, some don't... some have the joint to z-axis... some have the tip... what is with these guys and how would they be aligned most useful?

    Another thing is "Rest Pivot Rotation" I know what it does but when do I use it approperiate? Because you said something keep your bank rotation below 90 when I place the bone and "Rest Pivot Rotation"... after that it is 0 does this cause trouble in other ways?
    I read some articles of coordination systems which one are you using for setup / animation?
    ...
    it would be great if you could give some hints... I will try to fix my scene...

    thanks again...

    dines

  6. #6
    Yea, I was refering to T. Albee. In fact all of the things I was talking about are from that book pretty much.

    As regards the rotation bones, I'll heave to leave that to a more well versed rigger. I'd say use your common sense as far as what funtion the defromation bone is going to perform as to which orientation to place the rotation bone in.

    As to the other questions, they can all be summed up under gimbal lock and IK getting confused for that reason.

    So there are two thingns:

    1) record rest rotation (Shift P) which will record the rotation and at that point make it 0.

    2)Bone active (r) makes the bone active in its current position and rotation. But will keep the rotation of the bone in it's current state as far as the coordinate system is concerned. If the bone was rotated at 180 it will stay that way. That's how your rig wound up that way.

    It all boils down to what rotaion you are going to be performing.

    If you have prebent the arm, then you have a bone that is 90 on the pitch. However you also want to rotate the bone on the heading. This is problem for gimbal lock. It is also a problem for IK. So though you can change coordinate systems while animating to get around gimbal lock, it can still be a problem for IK as you know know, you can get flipping and such.

    So what you do is you record the rest rotation, which makes it 0 on the pitch in it's prebent form. That way all things start at 0. Ik is not confused and you can edit things easily while animating.

    As far as the coordinate system. I set everything up in parent which is the default. I use the other two to get out of jams if I need to.

    In the end it is all about ease of animation. You can use any coordinate system but then there are IK issues and then just simple logic as far as what you expect to happen while you are editing. Sometimes changing the coordinate sytem makes it more predictable for certain bones.

    You basically reset the bone using r anytime you have made a change to what you want it's rest position or rotation to be.

    I'm no expert by far. Hope this helps.
    Last edited by Surrealist.; 07-30-2005 at 05:55 PM.

  7. #7
    Lightwaver dines's Avatar
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    Thanks Surrealist for your help.

    I am still trying to fix it but everytime I made some changes and put in IK to work everything screws... I also tried to rebuild everything. But I think what I wanna do is, after Record Pivot Rotation and Rest Bone Postion, I also delete the goals and set them up new. Because I think they have some kind of rotation, too. How do you place your goals. Are you using the method discribed in T. Albee's book. (Turn off Parent in place->Parent goal to Bone-> turn on auto key and Parent in place-> unparent Goal from Bone)... or are you just moving the goals to the right position with out any rotation.... still a whol bunch of question and I appriciate your help very much thanks...

    dines

  8. #8
    Quote Originally Posted by dines
    Thanks Surrealist for your help.

    I am still trying to fix it but everytime I made some changes and put in IK to work everything screws... I also tried to rebuild everything. But I think what I wanna do is, after Record Pivot Rotation and Rest Bone Postion, I also delete the goals and set them up new. Because I think they have some kind of rotation, too. How do you place your goals. Are you using the method discribed in T. Albee's book. (Turn off Parent in place->Parent goal to Bone-> turn on auto key and Parent in place-> unparent Goal from Bone)... or are you just moving the goals to the right position with out any rotation.... still a whol bunch of question and I appriciate your help very much thanks...

    dines

    Yea I'm doing it just like the book. Keep in mind I have not got a lot of experience with this. I understand the theory pretty well and I set up a rig using the book but that is about it. I am emersed in modeling right now. Sorry I can't give you too much more and not being a guru in this area, I can't expound on goals. But I will say T Ablee's book gives you a very reliable set up and method so I can recomend doing it as he does. Hope this was a help.

  9. #9
    Lightwaver dines's Avatar
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    hey anyway it was great help... if pro or not you helped me and at least pointing me in some direction was a good inspiration...
    if you are interessted?... before I posted this thread I shood a thread on cgtalk... first it seemed that nobody replied... (that is why I tried it on cgtalk )... after a while I got now some posts... also one from t4d... which trasformed my rig and used a different approach to rig and control the hip/knee.
    So if you still in ... you could take a look at

    http://forums.cgsociety.org/showthread.php?t=262876


    dines

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