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View Full Version : Max animators please help!

Velocamonkey
05-23-2002, 09:07 AM
Right, deep breath prepare for a long one, MAX animators help please...

http://www.btinternet.com/~hull.family/Fcurve3.bmp

I've set up the simplest of tests to demonstrate my problem with F Curves. Just a small object moving across the screen using 4 keyframes.In the top picture the speed of the object is constant throughout, the red Trajectory
clearly shows that each frame is evenly spaced apart, thus equal speed throughout, simple. Okay?

Now in the bottom pic I want the object to gradually increase in speed between Keyframes 1 and 2, start to slow between 2 and 3, and then slow to a halt between 3 and 4.

So I fiddle with Custom tangents in F curves as this should give me the precise results I want. And the object definitely increases in speed, slows then slows to a stop.

But the problem lies in the interpolation between the changes in pace.

Looking at the trajectory: If you look at space A the object is moving its fastest I want it to gradually slow into this next stage but instead there is a slight jump so that what happens is :gradually speed up, slight jump in pace, slow down, slight jump in pace, slow to stop.

This slight jump in pace results from the spacing of the frames produced. Ie, A is wider because it is moving fastest, then B is smaller so it's slowing BUT then C is a larger spacing of frames than B, thus a jump before slowing.

Now I've tried for hours LITERALLY to play with this, I've adjusted the tangent handles so precisely, broken handles using shift etc... so I can get gap B to visually appear
to be the right size, but no matter what, because I guess it isn't mathematically correct the jump is still ever so slightly (and very annoyingly) still visible.

Now I know this doesn't have to be this way because I've seen smooth MAX animation but no one gives away any secrets where animation is concerned, but help if you can please!!?
:annoyed:
Iain McFadzen
05-23-2002, 10:05 AM
I don't really know why you are having problems, but I can see from the f-curve that you have a kink in it which is probably causing your woes. The second and third keys look like broken bezier keys set to slow in/ fast out, which will always make the motion "jump" a little. Change them both to smooth type keys (which will realign the bezier handles), then change them back to bezier and just rotate the handles around to horizontal (without breaking them), and adjust their length to get the ease in and out you are looking for. If I understand you correctly that will give the motion you are after.
Velocamonkey
05-23-2002, 12:43 PM
Yeah I get what you're saying, but it's not what I'm looking for. I think it's kind of hard to explain in word form.
Thanks for trying though.
Taoizm
05-23-2002, 05:11 PM
tell me if I'm wrong, but it sounds like you want to to accelerate off of Key1 and then decelerate into Key4. Why not strip out Keys 2-3 and just apply a slow out curve at key1 and a slow in on key4.

often times you have to go back and look at the curves and remove keys that make little or no difference to the animation. That's what it sounds like in this case.
Velocamonkey
05-23-2002, 05:54 PM
Taoizm, that actually made a lot of sense. The annoying thing is it's like having a bunch of points on a graph and getting a really crap line of best fit which means that rather than being a nice gradual change in speed it messes up at each point.

And the way round it does appear to be have less actual keyed frames and just get the slant right to get the desired spacing of tweens.

It's just a strange way to think, for me anyway. I had an idea of how I wanted it to work but it never did.

It just seems odd that there aren't any actual tutorials on this kind of thing, the tendency is a tutorial that's really detailed and then ends with "use the Function curves to make everything smoother". Which always leaves me thinking, wtf?

What really got on my nerves was that 3ds Max Indepth book on animation. There's a video of this skeleton walking and it's all smooth and flowing and they provide you the .max files, so I thought great I can look at how they go about F curves.

But it sux because the file that should be the "after f curves adjusted" is identical to the one where they aren't adjusted. They say that this "after f curves adjusted" is the one that they rendered to make the video, but I rendered it and it's not the same, it's stiffer and not as smooth!!

So it just lead to my paranoia that there is some great F Curve secret that no one's willing to give away.

Back to the padded cell...
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