An overview of IFF animation
AMOS Professional IFF animation files are divided into a number of separate components, the
"frames" of your animation sequence. A frame may be either a normal screen or one image in
the sequence, but it is important to understand that the first frame sets up the background
reference image for the entire animation, and this first frame is a standard IFF picture. All of the
following frames are then stored using the delta-encoding system, to be saved as a list of the
differences between the new image and the current display.
AMOS Professional offers several alternative methods of exploiting your animations, which may be displayed as an entire sequential video in a single operation, or played in any combination of frames, providing the sequence runs forwards. Maximum use is made of the double buffering system, to ensure smooth screen displays, although you are free to ignore this feature and summon up some flickering screen effects.
IFF animation can be used directly with most other AMOS Professional graphics commands, including SCREEN COPY and SCROLL, and you can experiment with any area that is not being currently animated. Obviously, if you try to draw over the area of the animation, the display will become corrupted. It should also be noted that IFF animation is not compatible with the standard Bob routines. When using Bobs, it is safe to hide the IFF animation on an invisible background screen and copy the results to the main display. Please see Chapter 7.3 for an explanation of updating objects. Of course, the easiest solution is to bypass the problem entirely and use sprites instead of Bobs!
It is important to remember that IFF animations can only be played forwards. Never attempt to run your frames in reverse order. A special function is provided for skipping over any frames you want to miss out.
You should be aware that even with delta-encoding, large, colourful and lengthy animations will still consume huge amounts of memory, but AMOS Professional can release this memory ready for re-use, as you are about to discover.
Creating an IFF animation
Many hours can be spent in the creative art of designing home-grown IFF pictures, and
adapting them for animation sequences. On the other hand, you can cheat! If a video digitiser is
beyond your budget there are plenty of public domain images to be found, but the most flexible
method is to use commercial packages like Deluxe Paint. III or IV. AMOS Professional uses
compressed" (Mode 5) animations, which should be selected from the menu of a commercially
available drawing package. Deluxe Paint uses this mode as a default, allowing you to draw your
frames one by one on the screen, and then generate the necessary ANIM files automatically.
Deluxe Paint users can produce animations using the following procedure: