About Fractanimate!
Fractanimate! allows the animation of (affine) IFSs defined by a few key
points in time ("key frames"). This page explains features and interface.
Go to the applet: Fractanimate!.
In order to describe where an animation goes Fractanimate! uses "key frames". Each
key frame is it's own Fractalina window,
describing the fractal of one of the frames that the animation goes through.
An animation must have at least two key frames, the first and last frames of the
animation, and can have more in between, to give finer control over the animation.
Key frames are like check points: Fractanimate! can decide how to go between key
frames, but it must end up at each key frame in order.
The number of frames between each pair of key frames is supplied by the user
(see below). Thus Fractanimate! will satisfy another constraint: not only will
it always go through key frames, but the distance, in frames, between them is
specified.
Fractanimate! generates the frames between pairs of key frames
by linearly interpolation. That is, the change in parameters between the key
frames is equally divided among frames in between.
As an example, imagine having two key frames in which the only difference is
the placement of one transformation: in the first it's at (0,0), in the second
it's at (8,8). If one frame is between these key frames, it will have the
transformation at (4,4). Similarly, if there are three frames they will have
(2,2), (4,4), and, (6,6).
Adding and removing key frames:
When Fractanimate is started two key frames will pop up (labeled 1 and 2). For a
simple animation (which goes from one fractal directly to another) these are all
that's needed.
To add a key frame enter in the text box right of "before:" the number of the
frame just after the one to be added, then press "Add Key Frame". For instance,
if you have key frames 1, 2, and 3, to add a key frame between 2 and 3 enter "3"
in the box and press the button. a new key frame 3 will come up, and the old 3 will
be moved to 4. (Another way of looking at this: enter in the text box the number
of the new key frame.)
To remove a key frame, enter in the text box right of "number:" the number of the
key frame to be removed, then press "Remove Key Frame".
Changing the number of iterations and size:
The size of the animation (in pixels, but not always real screen pixels) can
be changed from the Options window. To get the Options window press the button
labeled "Options" in the main control panel. After you have changed values,
remember to press "Accept", or the new values won't be registered.
When setting the size of the animation, remember that the memory usage to store
each frame goes up as the square of the size (memory can be important on
some systems).
Also in the Options window is the number of iterations per frame. Since each
iteration adds a point to the fractal, the number of iterations corresponds to
how complete the image is. A few thousand iterations is usually enough, but it
depends a lot on the fractal.
Choosing the number of frames:
There are two ways to choose the number of frames in between each pair of key
frames. If you want the same number of frames between each pair (or you only have
two key frames), set the number in the text box just right of "with". The
default is 4.
If you want to specify the number of frames between pairs of key frames, press
the "set up" button, and the Set Up Animation window will pop up. Each key frame
is listed, and in between each pair is a text box. Enter into this box the number
of frames in between the two key frames enclosing it. If you open the Set Up
Animation window and then change your mind, just press "cancel".
Making an animation:
Once the animation is set up it is easy to make it. If you have a Set Up Animation
window open, press the "Make Animation" button there. Otherwise, press the
"Make Animation" button in the main window. You will see each frame as it's
generated.
The play button and scrollbar:
To play back an animation after it has been made, press the "Play" button. The
scrollbar just above "Play" corresponds to which frame is being displayed. Notice
that the scrollbar moves while the animation is being played, and that you can set
the frame shown by changing the scrollbar.
Bounces and delay:
The "number of bounces per showing", and "delay between frames" can be found in the
Options window. The number of bounces is the
number of times the animation plays backwards or forwards (it will bounce back
and forth if this is more that 1). The frame delay is the amount of time to
sleep after playing a frame.
Dumping an animation to GIF files:
If the security manager allows file access (usually in the stand alone program,
but usually not in an applet) you can dump the frames of an animation to GIF
files. When the "GIF dump" button is pressed Fractanimate! will try to dump
each frame into a file called frmn.gif, where n is the frame
number. Once you have the gif frame images you can use a utility such as
GIFMerge to combine them
into an animated gif.
The gif dump function uses the excellent
GIFEncoder
class by Addam Doppelt.
Since each frame is stored as a Java Image, the memory requirements can
rise rapidly with the size of the animation. However, there is no set way that
Images are stored, so there is no way to know the memory usage. We have had the
most trouble with Unix systems, in which Images are stored in the X manager.
Interestingly memory doesn't seem to be an issue on PCs (including Macs). When
memory runs out each system handles it in it's own way. (Unix systems tend to
force the JVM to quit without a message.)
In the Options window you have to press "Accept" or the new values won't register.
This is not actually a bug, it's here so people won't write about it.
If you find any bugs not listed here, please
email to Robert Devaney.
Back