View Full Version : adjusting speed

04-28-2007, 04:05 PM
Ok, maybe I'm missing something really basic here, and if so, I apologize in advance. How do I animate/adjust the speed of a moving object without also affecting it's motion path?

I've tried making a simple bouncing ball, with 3 keyframes, one at the top of the bounce, another at the point of contact, and one more back up in the air.

I can adjust the tension and continuity of the middle key and get a nice looking motion path, and along with that comes an adjustment in the speed of the ball. (Starts slow, speeds up on the way down, then slows down on the way up again) Ok, so I like my motion path, now how to adjust the speed along that path without affecting the path the ball takes?

I can turn "show speed" on in the graph editor, but I can't make any meaningful change to my speed that doesn't also affect the motion of the ball, since as far as I can tell, I can't directly touch the speed/velocity channel, I can only affect the speed by adjusting my X or Y keyframes. And I don't want to adjust X or Y, because that also changes my motion path.

What am I missing here?

David R

04-30-2007, 08:41 AM
If you want the ball to arrive at a keyframe faster you'll have to move the keyframe itself. Example: I have a ball that is at 2m on the Y axis at keyframe 1 and falls to 0m on the Y at frame 12 (approximately half a second at 24fps). No matter how I tween my curves, those are the Y values of the ball at those frames for that half second. If I want the ball to get to the second Y value faster, the keyframe needs to be moved to a frame sooner than frame 12.


04-30-2007, 01:30 PM
Yes. And you can also scale all keys or a range of keys to shorten or lengthen the animation. Look in the manual or press F1 and search for "scale keys".

04-30-2007, 02:09 PM
I seem to recal Proton demoing a 'velocity' curve function somewhere- this allowed the sort of control you want (I think). It was a vid so it's probably archived in the tutorial section.

05-15-2007, 12:51 PM
So wait... are you telling me that Lightwave has no way to do a simple ease in/out to gradually change speed? I find that incomprehensible. I wasn't able to find anything in the manual, so I guess it doesn't. I use this function all the time when I'm animating in Flash or After Effects. I don't understand why Newtek could over look something so basic.

05-16-2007, 01:47 PM
That video is here (ftp://ftp.newtek.com/pub/LightWave/Tutorials/Vidz/Speed_Velocity.mov).

It is just another way to look at the curves from the perspective of speed and velocity.

As to whether or not you can ease in and ease out. In layout go to Help/Contents and in the search function type in "ease in ease out" and you will find a list of topics to study. For this to work you will have to load the help contents from disc. I am not sire how you do it for a trial. But the Graph Editor Curves Tab is a good place to start.

Any curve can be eased in and out. There are some advanced techniques to link many motions to one curve though expressions and so on. Just depends on what you want to do.

05-16-2007, 05:42 PM
One approach you can take to seperate an object's path from its speed is to use a motion modifier such as cyclist. You can set the path for an object and then use a second null to control the progress through that path. I generally will work to get the motion path to a constant speed and then can control speed entirely with the null. The trick is you have to get both sets of keys to be smooth using the graph editor for clean motion... so the techniques above are still very valid.

05-16-2007, 07:30 PM
Thanks for that. A perfect example. :)