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View Full Version : Feet slipping during walk cycle


Domarius
01-19-2007, 02:18 PM
I'm making an animation for Doom 3, which works with a bone heirachy that starts with everything parented to an "origin" bone. If you want your character to travel any distance during an animation, you have to move this origin bone, then animate the rest of the character to look like they walked there. (ie. origin is parent of hips, hips is parent of limbs...)

I'm animating a walking animation, and I have a problem with foot slipping, that I've been trying to sort out for 3 hours...

The foot makes contact with the ground. You put a key frame on it. You want it to stay there while the body moves forward. So when the hips move forward (taking the foot with it, since it's a child) you move it back where it made contact with the ground, and put a key frame on it. So it should stay on the ground in the same spot whilst the body moves forward, right? ****ing NO. It does some weird arse slide forward and backward again between the two points, still starting and finishing in the same spot, but with a wierd slip forward and backwards in between...

Adding "correctional" key frames to keep it still, winds up with you pretty much putting a key frame on every frame, and yet it still seems to wobble unsteadily, and this is a brutal, hacky, messy solution, that will be a nightmare to edit if I ever want to change the animation.

Opening the FCurves window to see if the bezier curves are causing some problems doesn't seem to help. I've set those keyframes to be flat (no curves for the movement, for translation and rotation) and they still do it!

There has got to be an easy solution to get feet to stop slipping. I've been reading about some arcane solution involving override clips or something, that I can't quite understand yet... surely there's some easy way to say "between these two keyframes, keep the foot HERE no matter what"?

(I'm using MotionBuilder 7.5)

Here are some animations showing what I mean. You'll have to take my word for it that the keyframes at the moment the foot makes contact with the ground, and leaves the ground, have the foot in the same place on the floor. The movement in between is not my doing...
http://208.49.149.118/TheDarkMod/temp/footslipping_perspective.avi
http://208.49.149.118/TheDarkMod/temp/footslipping_side.avi
(They use the xVid codec, which you can get here (http://www.xvidmovies.com/codec/))
Oh now that I've posted my anims, I should explain, its not a walking animation as much as it is a searching animation, sword drawn (will be placed in hand during gameplay), stepping forward carefully...

Sammer
01-19-2007, 11:46 PM
Hey Domarius,

It sounds like you might be combining two different workflows by keying the Master root of the character at the same time your keying the walk cycle.

I would say that 'generally' prople either key the walk cycle in place (so it looks like the character is walking on a treadmill) and then move and key the root in world space. Or they move the root to where they want the character in the shot and then leave it there and key everything else (hips, arms, legs etc.) never touching the root again.

Since your working on a game I would say it is probably more common to do the walk (run, sneak...) in place.

Good luck

Sam

Domarius
01-20-2007, 12:14 AM
Thankyou for your reply :) yes as far as I'm aware I am doing it by moving the root and then animating everything else to look like he walked there (maybe I didn't word that well enough at the start of my post there.)

That's the "origin bone". If I drag that around, the entire guy moves with it, like a statue, his limbs fixed in position until I move them directly.

So if I remove the keyframes from the origin bone, my guy will be walking on the spot.

I think what is happening is that because the feet are parented to the hips, they move around because the hips move around. So even though I have two keyframes of the foot in the one spot, the foot moves around even though there are no key frames happening because the hips are not moving at a fixed speed (they sway with weight balance, pitch forward to land on the foot, etc.)

IF this is the case (I may be wrong), then I assume there must be some sort of "lock to point in world" feature, where I can nail the damn foot to the floor on certain keyframes. :)

Sammer
01-20-2007, 01:04 AM
Gotcha,

Maybe something in this thread could help.

http://forums.cgsociety.org/showthread.php?f=85&t=388636&highlight=aux+effector

Domarius
01-20-2007, 02:50 AM
You guys have been great, thanks for attempting to solve my problem... you know what it was though... I wasn't keying the frame after I clicked the "Set discontinuity right (auto)" buttons to stop the curve interpolation from happening.

Who would have thought you need to press "Key" after making a change like that. I guess I always assumed it was directly modifying the keyframes.

Also I need to stop trying to do these sorts of things at 3am...

carlcarlson
02-07-2007, 06:07 PM
it sounds like you've got this figured out, but a solution I've found when having that problem is using the graph editor. for some reason Maya likes to insert curves between points that are the same some times. to fix that all you have to do is go into the graph editor and change that curve to a straight line. works every time for me.

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