KEY DRAWINGS / FRAMES

17 December, 2008

KEY DRAWINGS / FRAMES  - Animation principle

We know that animation is
nothing but a combined movement of individual frames. Key drawings are
communicators of your action.

 

In the above example, notice
the main key position that can communicate the whole action. Drawings at the key
positions are know as key drawings or frames, often called as poses. As the
number of in-betweens becomes evident the numbering of the key drawings will
change.

Keyframes:

Most commercially available
computer animation systems are based on animating with keyframes. At first, this
seems like the same thing as keyframes in traditional hand-drawn animation, but
it is slightly different, and therefore, you should approach your animation
differently. In hand-drawn animation, you work on the basic poses of the scene
first, drawing poses of the entire character so the timing and acting can be
worked out with a minimum of drawings created. Once the poses are finalized,
then the inbetween drawings are created to complete the action. With computer
animation, keyframes are values at certain frames for the articulation controls
of a model, which are usually set up in a hierarchy. The computer calculates the
inbetweens values based on a spline curve connecting the keyframe values.

When I first began animating
with a computer, I was used to hand-drawn animation and thought a keyframe in
one medium was the same as the other. So I worked on one complete pose, went
ahead a few frames, and then worked on the next pose. Well, the inbetweens
produced by the computer were completely useless. I ended up having a keyframe
at every frame to get the results I desired.

With computer animation, I
learned to work down the hierarchy of the model, and as I went, created separate
keyframes for the different controls at each level of the hierarchy. I found
that controls at some levels needed only a few keyframes where some at other
levels needed keyframes on practically every frame. I also found that I used far
fewer keyframes overall and the inbetween values that the computer would
interpolate for me were far more useful. The important thing with this approach
is to have a clear idea of the action you want to achieve before you start. Plan
out the action with thumbnail sketches and plot timing ideas on an exposure
sheet. Have these next to you as you block out the basic animation. You will
find that you will always refer back to these.

Key framing: 

Classical animators such as
Walt Disney developed Keyframe systems. An expert animator would design
(choreograph) an animation by drawing certain intermediate frames, called
Keyframes. Then other animators would draw the in-between frames. The sequence of steps to
produce a full animation would be as follows:

  1. Develop a script or story
    for the animation
  2. Lay out a storyboard,
    which is a sequence of informal drawings that shows the form, structure, and
    story of the animation.
  3. Record a soundtrack
  4. Produce a detailed layout
    of the action.
  5. Correlate the layout with
    the soundtrack.
  6. Create the “keyframes” of
    the animation. The keyframes are those where the entities to be animated are
    in positions such that intermediate positions can be easily inferred.
  7. Fill in the intermediate
    frames (called “inbetweening” or “tweening”).
  8. Make a trial “film” called
    a “pencil test”
  9. Transfer the pencil test
    frames to sheets of acetate film, called “cells”. These may have multiple
    planes, e.g., a static background with an animated foreground.
  10. The cells are then
    assembled into a sequence and filmed

With computers, the animator
would specify the keyframes and the computer would draw the in-between frames
(“tweening”). Many different parameters can be interpolated but care must be
taken in such interpolations if the motion is to look “real”. For example in the
rotation of a line, the angle should be interpolated rather than the 2D position
of the line endpoint. The simplest type of
interpolation is linear, i.e., the computer interpolates points along a straight
line. A better method is to use cubic splines for interpolation. Here, the
animator can interactively construct the spline and then view the animation.


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