Animation Concepts: Keyframes

Okay, while the sim caches are filling back up and I can't get any work done in SL I thought I'd blab about some animation concepts to help those new to it. I'll start with the most basic of animation concepts... the keyframe.

To understand the concept of keyframes it helps to have a little history of the terminology. The word comes from traditional 2D cel animation, and the division of labor in its production. In a tradional animation shop the labor would be divided between key animators and junior animators. The key animators only draw certain important, or "key" frames in the action sequence. Let's say the scene is of a character that's suppsed to run into a room, see a mouse on the floor, shriek in terror, and jump up onto a chair. The key animator would only draw certain pivotal frames in the action such as the character stepping through the open door, the character's glance to the mouse, the climax of the shriek, the character recoiling and crouched ready to leap, the peak of the character's arc through the air, etc. These individual drawings would be marked with a time of where they should fall within the animation sequence. These would then be handed down to the junior animators whose task it would be to draw all the frames "in between" the key frames. This is known as "tweening." The term "keyframe" then has two related meanings. As a noun, a keyframe is a pivotal frame in the action. As a verb, keyframing means to create those important, or "key" frames.

In the world of computer and 3D animation, keyframes still mean the same thing. The big difference is that your animation software (in this case, Poser) is your junior animator who will take care of all the tweening for you. Creating a keyframe is simply posing your character how you would like it at specific moments in time. Time in animation is determined by the number of frames per second used. The frame rate for NTSC video is 30 frames per second and is the default for most animation apps. 35mm film has 24 frames per second. PAL, the European video standard, uses sometething like 25 frames per second. For the purposes of creating animation for SL, 30 frames per second is what you want to use (See Xenon's comments below), and is the default in Poser. So, given that, to move to one second in the animation you would advance to frame 30, two seconds would be 60, and so on.

Let's say I want to create a three second animation of my avatar smacking himself in the forehead. Before I start animating I want to identify some key moments in the animation and where they should fall in time. I'd break this down into four key moments. The first would be the avatar having a sort of "AHA!" moment with his head tipping back slightly as the epiphany enters his brain and perhaps his shoulders bending back slightly. The second would be the "I'm gonna smack myself" moment where the head would come forward and focus straight ahead. The shoulders would come back to their original position and the right arm would come forward, bending at the forearm and twisting both forearm and wrist so that the palm of his hand is facing straight up. The third would be the moment of contact between palm and forehead characterized by the arm bending up while the head tilts foreward, with the palm in contact with the head. The fourth would be the recoil from the blow with the head thrown back, a bit of backward bend at the waist, and perhaps a small step backward with one foot.

To create this animation I would move the time slider to the moment in time where I'd like that first key moment to occur. I'd want to make sure that I didn't reposition the avatar at frame 0 so that when the animation starts the avatar is posed close to the SL default pose allowing for a more seamless blend from default animation to my custom animation. I've decided I'd like that first "Aha!" moment to happen at one second into the animation so I set my time slider to frame 30. I'd then pose my avatar as described above. By changing the pose of the avatar at a frame other than 0 I've just created the beginnings of an animation.Poser automatically does the tweening between frame 0 and frame 30. I'd then advance the time slider to the moment in time I'd like my character to be in the "I'm gonna smack myself now" pose. And so on.

To understand and be able to predict what will happen in the in-between frames there's a visual analogy I like to use. Imagine that time is represented as a slope going up at a steady incline and the total length of the slope is equal to three seconds. When I create a keyframe by adjusting any part of my avatar at frame 30, it's like placing a ball on that hill one third of the way up. That ball will then roll backwards down the hill (and backwards through time) until it either reaches 0 seconds in time, or it encounters another keyframe for the same specific body part. Let's say I bend my avatar 90 degrees at the waist. The resulting animation would start at frame 0 and bend over 1 second to reach my keyframe at frame 30. Because this is the first keyframe I've created for the waist, that ball will roll all the way down the hill back to frame 0, creating the in-between frames by dividing the total change in rotation by the number of frames between the moment in time I keyframed the bend to frame 0 and then rotating the waist by that amount on each frame. Now let's say at frame 60 (or two seconds into the animation) I bend the waist backwards by 90 degrees. When I put that ball down on the hill of time, it will only roll back to frame 30 where the previous keyframe for that joint was placed. In-between frames would be created between frame 30 and 60.

Now if at frame 90 I bend the elbow by 90 degress, that ball will roll all the way back down the hill to frame 0 because it is the first keyframe I've created for that joint. Because of this, sometimes you need to plan ahead for what moment in time you want a body part to start moving. If I wanted the elbow to wait until two seconds in before it starts bending then I would have needed to first create a keyframe for that elbow at frame 60, even though the bend amount for the elbow would be no different at frame 60 than it was at frame 0. You can think of that kind of keyframe where no movement is actually taking place as if you were erecting a wall on the hill at that point in time so that when you go forward to frame 90 and bend the elbow, it's ball will only roll down the hill to frame 60 where it will hit the wall and stop tweening. Another way to think of keyframes is that they are like bookends that section off segments of time. If I want a particular motion to only occur over a specific segement of time within the animation, or I want to make sure that a part of the body doesn't move during that segment of time, then I need to create bookends at both ends of that time segment.

Okay, wow... that turned into quite the novel! hehe. I hope the above discussion helps you understand the concept of keyframing a bit better and gives you some insight into the way keyframe animation is created in an application like Poser. Happy animating!

Fantastic info, Chip -- thanks!

Only thing I would add is that I recall a Linden saying that 30fps is probably too fast for animations given lag and varying graphics cards etc and that 15fps is probably a safer bet. I've done all mine at 15fps and they seem to run nicely and, as I understand it, should perform better in laggier situations.

I'll look around for that thread...

Nic

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Edit: found it:
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Thanks Nicola The few I played around with in the preview I did at 30fps and they seemed to work fine. Glad you mentioned that though. I imagine it may take some experimentation before we figure out what the best fps rate is for dependable playback in SL.

Thanks for finding that Nicola!

Thanks, Chip. That was EXTREMELY helpful.

I tried playing with Poser last weekend and finally had to give up.

About halfway through your second paragraph, the Universe fell into place, so to speak.

There's no penalty for uploading animations created at 60 fps vs 15 fps in SL, storage- or playback performance- wise.

My suggestion to animate at 15 fps is simply to help insure that the important details of your animation come through when they are playing back at different fps on different viewers, 15 fps being about the average viewer framerate.

As an extreme example, think about animating a character doing a series of hypersonic jumping jacks. With 2 keyframes set for each jumping jack (open arms/legs and closed arms/legs), if you animate at 60 fps you could create a maximum of 30 jumping jacks in one second. But if that animation played back on a viewer running at only 15 fps, the playback would essentially skip 3 out of 4 frames and all that detail you took the time to animate would be lost.

If you re-create the same animation at 15 fps, you could animate about 7 distinct hyperjacks in one second. If that animation played back in a viewer running at 60 fps(rare, but it happens ), the viewer would interpolate the motion between those keyframes and you would see 7 very smooth, distinct jumping jacks, actually improving the quality of your animation without loosing detail.

Really, you should animate at whatever framerate you are comfortable with since you can always retime the animation later at a lower framerate to test, or even check it in SL's animation preview window. You might try animating at 24 or 30 fps, since those are standard rates for film and video. 12 fps is the bare minimum for most people to perceive the illusion of motion, and most people can't discern more detail in motion above about 60 fps.

-Xenon

Thanks for the explanation Xenon! I have a hard time getting my brain around there not being a fixed playback rate. It makes more sense to me now. I'm too used to doing stuff for video.

and thanks, Grim Glad it helped.

Thats really helpfull Chip, thanks.

One thing that I am confused on is the Frame counters at the bottom.

If I have my frames per second (FPS) at the default 30 (done on the animation details window? with all the graphs and tables) then I change the counter at the bottom from the defualt 30 to 60...

do I now have a one minute animation sequence at 30 FPS?


Oh and thanks for stopping by and explaining that Xenon.

This one I can answer.

What you have is 60 frames, not 60 seconds.

60 frames at 30 FPS is two seconds worth of animation.

What Grim said The counter at the bottom just shows you the current frame and the total number of frames in the animation. You can change the frame rate (fps) in the Animation menu under "movie output settings." The next ones I do I plan to follow Xenon's advice and animate at 15fps instead of 30fps.

Ahh i get it now thanks. I suppose I should read the manual someday.

I think I'll try out 15 FPS too tonight.

Excellent!


Thank you Chip

Can someone move this thread to the new animation forum? It belongs there now

edit: Thanks!

I've found myself setting keyframes every 10 frames in my animations, fram 1, then 10, 20, 30 and so on.
Then I tweak the frame reate to between 15-20 fps until it plays smooth and natural looking.

OMG! Ding! the light comes on! *applauds*

I have a good question for you all, is there a way to get into a keyframe to change the speed?? and another question i have fiddled with my figure in poser and tried many time to make a butt wiggle animation.. how would i go about this???


Aces

You can tweak the speed at which things happen in your animation by moving the keyframes in the animation palette (also known as the dope sheet). If a part of your animation goes too quickly then you need more frames between your keyframes that bracket that specific part of the animation.

If you look in the dope sheet you'll see two kinds of green blocks. Some will be bright green and some will be dull green. The bright green ones are your keyframes. Those are the ones you specifically created by adjusting the pose of the avatar at that frame. The dull green ones are the tweens that poser created. You can click and drag on the keyframes to move them to a different frame. Moving a keyframe will change the timing of everything that happens between the key that preceeds it and the key that comes after it, and poser will recalculate the tweens in those sections.

To do a butt wiggle you need to animate hip rotation since you can't animate the buttocks themselves. Hope that halps

edited for typo

Hugs Chip,


I will sure try what you suggested.. Ty again

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OMG Chip, thankyou. I didn't know you could move the keyframes around on the dope screen (I didn't know it was called a dope screen), I'd been wanting to move my keyframes but didn't know how. I'd been using the pose dots for the pose in the keyframes that I wanted to keep and then setting the keyframes at a different spot and the pressing the pose dots.
I'd also like to thank Lumiere Noir for telling me how to clear the pose dots as they stay there forever until you delete them, (press ALT and left click withthe mouse on the pose dot to delete).

ok, I have had the concept of keyframing down since birth, just something that made sense to me. BUT, is there any tutorials for moving things in poser, or a best way of doing it? I mean my dude gets so screwy by the end, and then the imported animation just isn't what I was expecting. Should I change from the shaded posing mode to something else? I haven't checked if there is just a bones animation method or what, but I just want to know the best method. Or maybe it just takes all kinds of practice.

thanks

spin54

I'm not a very experienced Poser user, but I find that trying to directly manipulate body parts is a bad idea. I do everything with the parameter dials.

hehe, I don't even know how to use the pose dots. I HATE Kai Kraus style interfaces. It's like he sits around trying to figure out how to make the least intuitive interface humanly possible. Give me functional over pretty any day.

Just think of using the pose dots as a camera.. select a keyframe or pose you want to keep, click an empty pose dot... then move on.. you want to recreate that pose again.. click pose dot and the poser man is back in that pose.

Yeah the Kai Krause interfaces took a while for me to get used to.. now I dont wanna change... hehe

Is there's anyway to shift the whole animation's keyframes along say 5 frames? I wanted to add frames in at the start and the only way I can figure out how to do it is to open a new file, then import or open a fileso that it gets added after the opening frames. Or something like that....

I'm not sure if you can use the retime animation feature to time shift or not, but if worse comes to worse you'll have to move all your keyframes manually. Unfortunately I don't think you can move multiple rows of keys at a time, but you can do whole horizontal rows bye shift selecting the first and last keys in the row and then dragging them (at least I think you can drag multiple keys at once). If dragging doesn't work, shift select the whole row, do edit/copy, delete the whole row, select the frame five frames after where your first key was, then do edit/paste.