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View Full Version : Basic FK set-up problem / questions.



medicalart
02-03-2008, 02:37 PM
Sadly, I've been working on this for many, many days and can't get things to work. (See attached sketch). I'm trying to get a loop in the middle of a hierarchy to form using FK. I started to adjust in the middle (bone 7) at frame 1 and worked one frame at a time and one bone at a time. Because the curve reverses, everything I work on gets undone.

I'm trying to figure out the best approach.
To use all FK, it seems like I'll need to start with the last frame (frame 50) and then work my way back to frame 1 --AND-- start with the parent bone in the hierarchy and then adjust each child bone.
Is this correct?

I've tried some plug-ins and IK over the past few weeks and can't seem to control things which is why I'm back to FK. Any suggestions?

The actual hierarchy has 60 bones. The sample is a simplified version. Thanks.

pooby
02-03-2008, 02:53 PM
have you tried the plg curve bone plugin.. you could do this with ease in a matter of minutes. what's more, the transition would look nice. An FK one will look awful without tons of work.

Dodgy
02-03-2008, 04:14 PM
Definitely the PLG Curve is the way to go here:
http://homepage2.nifty.com/nif-hp/index2_english.htm

medicalart
02-03-2008, 05:21 PM
PLG curve has been recommended and I've looked into it but didn't readily see any advantage before. Will try to set something up on your recommendations.

BUT back to the original question. What's the proper approach if someone were to try and do this with FK? Lock and unlock bones? Do frames in reverse order? Any suggestions?

medicalart
02-03-2008, 10:10 PM
It's taken quite a while to set this us using PLG curve. The plug-in works ok, but not for tight curves and the tiny loop I'm trying to form. I'll try a few more things, but if anyone has any other ideas on how to maintain tight control of a hierarchy, let me know. Or an approach to using FK. Thanks.

pooby
02-04-2008, 02:02 AM
There is no approach with simple FK that will work well- Its just innapropriate for this.
The reason being that you need a control that will conform the bones to a shape on every frame, like Curve bone.. without that you are limited to a parental chain which will have an additive movement down it.

Curve bone WILL work. If you're having problems with tight corners, just use more bones.

pooby
02-04-2008, 02:08 AM
There is no approach with simple FK that will work well- Its just innapropriate for this.
The reason being that you need a control that will conform the bones to a shape on every frame, like Curve bone.. without that you are limited to a parental chain which will have an additive movement down it.

Curve bone WILL work. If you're having problems with tight corners, just use more bones.

druitre
02-04-2008, 03:54 AM
what's more, with PLG you can split bones (with LW's split bones command) in a chain and in that way create more bones to fit tighter corners without the whole thing breaking apart. You could start with a rough setup, animate that and not worry about the corners being too coarse, then split bones and refine after. Same thing with the control nulls - if you run into some unwanted behavior, you can add controllers quite easily. The whole PLG plugin is very stable and will retain whatever you've done so far.

medicalart
02-08-2008, 07:49 PM
Thanks. Good suggestions but I'm still having PLG problems. Can I use PLG_curve plugin in a rig which has base-to-base bones? (see photo) or do all of the bones have to be oriented in one direction? If I can use them in 2 directions, do I need to set up two separate PLG curve chains? Or can I just do one (even if it means only going half-way.) I'm getting weird effects and I don't know if I'm making mistakes or if it's not meant to function this way.
Thanks.

medicalart
02-08-2008, 07:56 PM
what's more, with PLG you can split bones (with LW's split bones command) in a chain and in that way create more bones to fit tighter corners without the whole thing breaking apart. You could start with a rough setup, animate that and not worry about the corners being too coarse, then split bones and refine after. Same thing with the control nulls - if you run into some unwanted behavior, you can add controllers quite easily. The whole PLG plugin is very stable and will retain whatever you've done so far.

Druitre, (or anyone) would you happen to know how to go about creating more bones the way you described? The first half of my animation was fine but I needed more bones for the second half. At frame 0, I used bone split but that changed everything in the animation. (I split one bone into 3 small bones.) Is there a good way to do this? I tried to adjust bone strength to compensate for the former bone. Do I need to rest the bones again? And I couldn't get PLG plugin to compensate. Thanks.

druitre
02-09-2008, 10:08 AM
Here's a quick test, I'm not sure though if this replicates your issue.

I set up a chain with four bones, added three nulls and then added plg-curve bone to each bone in the chain and plg-curvebone-top to the first bone, added the first two nulls as controllers. The last bone on 'goal' to the third null, fulltime IK. Rest all bones, make sure IK is on.

I animated the three nulls, the chain folows along, trying to match the nulls' positions but because it's only four bones this is not very precise. That's in scene setup_4_bones.lws.

Then I split each bone into two, added plg-curve to all the new bones, switched the goal/fulltime IK from the first-to-last to the last bone and then deleted the control entries in the first bones' plg-curvebone-top interface and then re-added them (this seems necessary to reset plg). Rest all bones, activate IK. That's setup_8_bones.lws

Once again I split every bone, now I end up with 16 bones. Scene setup_16_bones.lws.

Each time, the animation on the nulls remains the same and so does the response of the bonechain, except the more bones there are, the more exact it can follow the positions of the nulls.

54588

Let me know if this doesn't answer your question!

Jasper

medicalart
02-09-2008, 10:30 AM
Jasper, Thanks for posting the scenes and doing the tests. I used your suggestion to delete and re-add controllers to reset PLG and that worked. I also looked at your scenes and will try to improved my rig based on what you've done. Steve

druitre
02-09-2008, 11:30 AM
A thing that might be useful to keep in mind is that whenever two controllers get too close to each other plg will start to jitter, twitch, or flip. I did a little animation with the 16-bone chain to illustrate; I took care to add some keys to the controllernulls so that they wouldnt cross paths and would maintain more or less equal distance all the time.

Now that I write this, it would probably be a good idea if you'd add a motion modifier to the nulls (relativity maybe?) to automate this.

54589

medicalart
02-09-2008, 12:11 PM
YES, I had that problems yesterday. Today things are even worse. I can't seem to get PLG to affect the rig at all. I'm not sure why this is happening at this point. I reloaded the controller nulls but still doesn't work. Your suggestions are great so I'll implement them--once I get things working again. Thanks.

medicalart
02-10-2008, 11:06 AM
Another question: I'm currently using PLG curve to steer the rig--thanks to this thread!-- now I'm wondering if it interferes with IK goals? (I posted this elsewhere about goals).

I have two rigs parented to the null, but the tail of the top one slides around when the null moves. (The lower rig is ok.) I tried making the null a "goal" for the last bone in the top rig with a goal strength of 1000, but it still won't stay stuck to the null. I want to be able to move that top rig around but still have the tail stick to the null. Any ideas?

medicalart
02-10-2008, 01:24 PM
I may have figured this out. PLG controller nulls need to be parented to that junction null, and not to the object they control, in order to have things work properly. At least that's the way it looks right now.