Stuff happening between keyframes?

Hi there

Sorry for the silly newbie question, I'm very new to poser. (I completed Ulrika's awesome tutorial just hours ago)

I've made a couple of poses, and now I'm trying to move onto animations.

I'm trying to make a 3 second 90 frame animation.

The first 30 frames are okay. I added a keyframe on frame 30 and frame 90 which are identical, with absolutely nothing going on in between. (In the keyframe editor window, it seems to confirm that there's no data between these two keyframes)

Why is my avatar doing silly stuff like poking out his head with his hand between frames 30 and 90?

Francis, it's most likely because Poser applies a bit of smoothing/blending between keyframes by default. It's intended to keep your animations from looking robotic, but it often causes problems where the motion will continue past the keyframe. The best way to troubleshoot and fix unwanted motion is to use the graph editor.

Attached is an example graph. There are only three keyframes. The horizontal axis of the graph represents time. The vertical represents amount of change. Notice in the graph on the left how the red line curves up and back down between the first two keyframes. Both keys have the same value but because of smoothing there's motion between the two keys anyway. The graph on the right shows it fixed by inserting a couple of additional keys to keep the line horizontal between the first two keys.

Hope that helps

Chip,

Thanks for the tip. I think you're right. There's some cubic spline interpolation which does really odd things, so it can lead to unpredictable results.

I got around my problem by inserting more keys, like you suggested. I'll look into seeing if I can turn off splines and go to good ol' linear interpolation later.

I think you'll find that the interpolation saves you more time than it costs. You just have to get in the habit of checking the graph. Fixing a few overshoots is preferable to manually doing ease in and out for every key

Fran, if you dont want any movement in between the keyframes, set all the keyframes at frame 30 to be linear instead of spline.

edit: oh I just noticed the last thing you said about switching to linear, is there any reason you wouldnt want to?

Yes. Because if you did, your entire animation would look like mr. roboto and you'd spend a lot of time going in and adding extra keyframes to smooth it out. Smoothing is generally a good thing, though there are certain instances that cause the interpolated spline to overshoot the keyframe. With a bit of practice you can fix these kinds of problems by simply looking at the graph and not even previewing the animation. It just becomes force of habit.

Hey guys

Thanks for your thoughts. My question: how do you turn on linear mode? I'm not very familiar with Poser UI.

Chip - gwin showed me a better solution than adding more control points. There's this button in the keyframe editor that's called "break spline" or something like that. Break the spline - no more need to add control points.

Arch - There's no particular reason that I wanted linear, other than it's more intuitive. Does poser support different types of splines? I think Poser (by default) is using cubic hermite splines which are first and second derivative continous. That second derivative continuity is the reason for the "overshooting your control points" goofyness. Is there a way to turn that off, maybe using a Catmull-Rom spline or something?

The only problem with that is you lose the "ease out" from the key where you break the spline. In the example graph I posted there's no movement between the first two keys. Movement starts at the 2nd key and continues to the 3rd. If I had broken the spline at the 2nd key, the line between the 2nd and 3rd keys would be straight, meaning that the motion would start at full speed instead of ramping up. That usually looks bad. In order to fix it you'd have to go in and add a couple more keys right after the 2nd key instead of right before it as I did in the example. It might not be problematic in SL since we rarely see anims play at full framerate, but I'm used to animating for video where going from dead stop to full speed isn't a good thing unless you're animating a robot.