           Subject: The -Color-Scroller-
                By: James Collett (Professor)
       A Member Of: VIRTUAL INFINITY
              Date: April `94
           Address: Park View Farm, Carlton, Nr Nuneaton, Warks, CV13 ODA
          Internet: s6005146@brookes.ac.uk
      Mono Account: bcc


    This Screen Is Public Domain
    ============================
        This means it may be freely copied and distributed *providing*  the 
    following four files remain TOGETHER and UNALTERED:

               scroller.txt        - this file
               scroller.gfa        - main screen
               tables\st_pal.gfa   - palette generator for 8MHz
               tables\falc_pal.gfa - palette generator for 16MHz


    Also On Disk
    ============
        The following two files should also be with the screen:

               tables\st_pal.dat   - palette data file for 8MHz
               tables\falc_pal.dat - palette data file for 16MHz

        However,  if  either of these two files are missing,  don`t  panic! 
    Programs  are included to allow palettes to be created  and  customised 
    (discussed shortly).


    Running The -Color-Scroller-
    ============================
        The  first thing that`s needed is a copy of GFA Basic  3.   If  you 
    don`t  have  it,  WHY NOT?!?   Assuming you have  GFA  3,  the  -color-
    -scroller- only runs in ST low res compatible (320 * 200 * 16 color).

        The  main program,   scroller.gfa,  has (hopefully)  been specially 
    written to run on both 8MHz machines (e.g. ST) and 16MHz machines (e.g. 
    FALCON).   As explained when the screen starts up, I`ve not yet figured 
    out  a way of determining the processor speed which works on ALL  ATARI 
    machines.  So at the minute YOU have to tell the program what speed you 
    have (by pressing '8' for 8MHz or 'space' for 16MHz).   [If you`re  not 
    sure, run both versions and see which looks best!]

        After showing the credits,  the program should load the appropriate 
    palette  data file and run the scroller.   The 8MHz  scroller  consumes 
    some 1800 colors a second, and the 16MHz version burns up no fewer than 
    3600 colors a second - not exactly environmentally friendly!!
    
        If the program reports a "File Not  Found"  error then you`ll  have 
    to create the  palette  data  files (discussed shortly) before you  can 
    run the main program.   If you don`t like the color scheme or get bored 
    of  it,  you  may like to customise the palette data  files  (discussed 
    shortly).


    Bugs / Incompatibility
    ======================
        The 8MHz version has been tested on an STe,  and the 16MHz  version 
    has  been  tested on a FALCON.   It #may# be that the timing`s  out  on 
    other  ATARIs (TT,  MegaST,  etc) despite the fact their 680x0 runs  at 
    8MHz or 16MHz.   This may be due to blitters,  co-processors,  resident 
    programs, etc.

        If a screen doesn`t work on your machine then PLEASE report the bug 
    (too fast, too slow, etc) and your setup (8MHz processor, 8MHz blitter, 
    etc) to the screen`s author!


    Creating And Customising Palette Tables
    =======================================
        Both versions of the -color-scroller- 'cycle',  or scroll, palettes 
    up the screen.   The 8MHz version uses 6 palettes (numbered 0 to 5) and 
    the 16MHz version uses 12 palettes (numbered 0 to 11).   These palettes 
    are not calculated in realtime as it`s difficult to calculate  "pretty" 
    color  schemes!!   Instead the 'palette tables' are stored in  external 
    data   files:   the   8MHz  scroller  uses  a   6-palette   data   file 
    (tables\st_pal.dat)  and the 16MHz version uses a 12-palette data  file 
    (tables\falc_pal.dat).

        Two additional GFA programs are included, in the tables\ folder, to 
    allow the respective palette data files to be created (if missing)  and 
    customised - i.e. to allow palette data files to be 'generated'.

        Each  of  the 6 (or 12) palettes consists of a  'BASE  COLOR'  (for 
    example medium red with a tinge of blue: &401) to which you add 'RANDOM 
    INTENSITY' to produce a range of shades.   For example adding a  random 
    intensity of 4 to a base of &401 will generate shades with reds between 
    4 and 7,  greens between 0 and 3 and blues between 1 and 4.   In  other 
    words shades between &401 and &734.

        The list of base colors for the palettes is contained at the end of 
    the table generator program.   Each palette`s base color  'description' 
    should be of the following form:

          DATA red_on,red_base, green_on,green_base, blue_on,blue_base

        There  should  be  as many base color  descriptions  as  there  are 
    palettes - i.e.  tables\st_pal.gfa should contain 6 data lines (one for 
    each palette) and tables\falc_pal.gfa should contain 12 data lines (one 
    for each palette).

        Each   base  color  description  should  contain  six   values   as 
    illustrated above:  the first two for the red COMPONENT, the second two 
    for the green component and the last two for the blue component.   Each 
    component_base  should be in the range from 0 to 7  (inclusive).   Each 
    component_on value acts like a "switch",  and should either be set to 0 
    if you wish the component off or 1 if you wish the component on.

        If you`re unsure about setting the base colors or random intensity, 
    the  best thing to do is EXPERIMENT!   Once you`ve set the base  colors 
    and  random intensity,  simply run to generate a palette data file  for 
    the  main  -color-scroller-  (ensuring the data file is  saved  in  the 
    tables\  folder).   You  may  also like to save  the  actual  generator 
    program, to save your base color and random intensity settings.

        Important:
        ~~~~~~~~~~
        If  the sum of any component base (for any palette) and the  random 
    intensity is greater that 8,  then it is likely you`ll have intensities 
    greater than 7 in your data file.   At best this may not look  "pretty" 
    (!), at worst in may be incompatible with your machine.  If you have an 
    STfm  compatible (3 bit) palette,  for best results always ensure  'the 
    sum' cannot exceed 8.   If you have an STe compatible (4 bit)  palette, 
    for best results always ensure 'the sum' cannot exceed 16.


    And Finally
    ===========
        Although  there  is no financial charge for  the  program,  support 
    appreciated.  You can support in two ways:

    1) by  distributing  the programs to everyone you  know,  ensuring  all 
       files remain together and unaltered,

    2) feedback:  all comments,  queries,  error / incompatibility reports, 
       ideas,  suggestions,  etc are welcome - both positive and  negative. 
       My postal and E-mail addresses are previously listed.


    ---END---
