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yevlar
03-26-2005, 10:47 PM
I'm in the process of setting up my first fully boned character (and after 9 years playing with Lightwave, it's about friggin time!) and I'm having a few issues with the IK on my character's legs.

The IK is working beautifully, and I'm happy with the deformations. However, when I was starting to set up a walk cycle, I noticed that, when moving the legs' IK goals along the Z-axis, instead of the foot staying locked to the ground (and the goal) the foot raises up away from the goal. "Match Goal Orientation" is activated.

I turned on "Keep Goal within Reach," which just locked the goal to the rising foot, which isn't exactly what I want.

Also, when I move the character's center-of-gravity down, I notice that the Goal moves with it for about a meter, then pops back to its proper position (which, naturally, plays hell with the deformations.) Moving the center of gravity up pulls the goal up with it, which I don't think is supposed to happen (the goal is not parented to anything.)

Increasing the goal strength does nothing to stop these issues.

The character, just so you know, is a Penguin, so the legs are very short and stubby. I used the bone structure of a human character as a basis for this, just because I want the penguin to have some more human-like movements. Could this be part of some of my problems?

I'm also using Lightwave 6.5 (can't afford the upgrade to 8 yet.)

Dodgy
03-27-2005, 09:07 AM
Did you put a little bend in the leg (before setting up IK) to tell the Ik which way it should bend?

yevlar
03-28-2005, 06:21 PM
I tried putting a bend in the leg, but it doesn't seem to do anything. The bones for the thigh and shin appear to be locked in the same plane- they aren't bending independent of eachother.

Celshader
03-29-2005, 11:15 AM
I'm in the process of setting up my first fully boned character (and after 9 years playing with Lightwave, it's about friggin time!) and I'm having a few issues with the IK on my character's legs.

The IK is working beautifully, and I'm happy with the deformations. However, when I was starting to set up a walk cycle, I noticed that, when moving the legs' IK goals along the Z-axis, instead of the foot staying locked to the ground (and the goal) the foot raises up away from the goal. "Match Goal Orientation" is activated.

I turned on "Keep Goal within Reach," which just locked the goal to the rising foot, which isn't exactly what I want.

Also, when I move the character's center-of-gravity down, I notice that the Goal moves with it for about a meter, then pops back to its proper position (which, naturally, plays hell with the deformations.) Moving the center of gravity up pulls the goal up with it, which I don't think is supposed to happen (the goal is not parented to anything.)

Increasing the goal strength does nothing to stop these issues.

The character, just so you know, is a Penguin, so the legs are very short and stubby. I used the bone structure of a human character as a basis for this, just because I want the penguin to have some more human-like movements. Could this be part of some of my problems?


IK is a big game of "tag" for the computer. LightWave tries to make the pivot point of the end of the IK chain touch the pivot point of the goal object, using the IK-controlled channels of that chain.

If you pull the penguin far away enough so that the distance between the IK goal and the start of the leg's IK chain is greater than the length of the leg, the foot will pull away. It must pull away, because the leg's not long enough to touch the goal.

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It sounds like the IK still needs to be "programmed" to bend. IK tries its hardest to stay close to the initial value of each IK-controlled channel. In other words, it will maintain the character's earliest keyed pose if it can. If a leg is ramrod-straight on frame -100 and bent completely from frames -99-and-up, IK will note that the leg is ramrod-straight on the earliest possible frame and do its best to maintain that pose for the entire animation. Make sure the legs are bent on the earliest keyed frame of the entire scene. It doesn't have to be a key for the entire body -- just the IK-controlled channels.

"Keep Goal Within Reach" does not affect IK solving at all. It's an interface option for IK. "Keep Goal Within Reach" will automatically move the goal object to the end of the IK chain if the IK chain runs out of length. It can sometimes make the IK goal easier to grab, but I usually leave it turned off.

yevlar
03-29-2005, 12:06 PM
YEEEEESSSS!

That was exactly the issue. As soon as I set those bends on Frame 0, everything started working properly.

Thank you!

Celshader
03-29-2005, 05:18 PM
YEEEEESSSS!

That was exactly the issue. As soon as I set those bends on Frame 0, everything started working properly.

Thank you!

Cool. Glad to help. :)