GED v.2 - See the end of this document for new changes.¢¢GED is not a full featured drawing program. I have used it only for¢doing color and simple pixel cleanup. It is also the only self¢contained program right now that can display this graphic format.¢¢GED, and the code which it contains, are not public domain. It is¢freely distributable though for non-commercial applications. Please¢contact me if you wish to use this graphic format in a commercial¢product. GED is (C) 1993 by John Harris.¢¢GED OVERVIEW:¢-------------¢¢GED was designed to create the best possible flicker-free graphics¢that the Atari can display. It uses almost 10K of inline code to¢continually stuff new colors into the color registers, allowing up to¢9 playfield colors per scan line.¢¢GED can also place PMGs anywhere on the screen. You may change the¢width, color, and priorities. GED can change one graphic register per¢scan line, allowing you to reposition PMGs for multiple uses. GED¢tries to be as flexible as possible with PMG editing, so that you can¢simply position and draw wherever you wish. However there are limits¢to what the program can do, and it may be beneficial to read the¢TECH.DOC file, to get a better idea for what is going on.¢¢The bottom line of all this, is that you can get up to 14 colors per¢scan line, and 9 of those can change every line. Plus having full¢control over all of the graphic registers, and being able to change¢one per scan line.¢¢GED DRAWING:¢------------¢¢The joystick can be used to move the cursor. The movement may appear¢choppy at first, but the stick routines are designed to allow single¢pixel movements by tapping the stick in any direction. Even diagonals¢can be moved without getting horizontal or vertical 'tails' on the¢diagonal lines.¢¢The cursor can also be moved with the arrow keys. The keys by¢themselves will move 1 pixel. With Contol pressed, it will move 8¢pixels.¢¢Shift-Control-Up will take the cursor to the top of the screen. This¢will be useful for changing player/missle registers, as described¢later.¢¢Press the fire button on the joystick to draw with the active color.¢If the pixel was already the active color, at the location where the¢fire button was first pressed, then pixels will be erased with the¢background color as long as the button is held down. This allows easy¢plot and erase of a particular color without having to select colors¢from the keyboard. The tradeoff, is that you must make sure you start¢drawing on a pixel that is a different color to prevent going into¢'erase mode'.¢¢To change the active color register, use the keys 0-3, with 0 being¢the background color. You can also move the cursor onto a color you¢wish to draw with, and press 'G' to grab that color.¢¢To clear the entire screen, press the keys Shift-Control-Tab.¢¢Press Shift-X to exit to DOS.¢¢FILL MODE:¢----------¢¢Press the Spacebar to toggle between drawing mode and fill mode.¢There is an icon at the top of the screen to indicate what mode you¢are in. It will be a line in draw mode, or a filled box in fill mode.¢The cursor flash rate will also be faster in fill mode, as an¢additional visual cue.¢¢Fills may also be made in dither mode. Press the 'D' key, followed by¢a number from 0-3. A crosshatch dither will be formed between this¢number, and the active color register. The icon will show a dithered¢box when the dither option is set. Press D again to return to solid¢fill.¢¢The fill mode in GED is a simple top down fill, within the borders of¢the color register where the fill was started.¢¢Press 'U' to Undo a fill operation.¢¢The fill mode currently fills only the color register. Color palette¢settings are not carried with the fill, and these may need to be¢copied manually with the 'C' command. (Described later) This will¢likely be improved in a later release as well.¢¢PLAYER/MISSLE EDITING: (PMG)¢----------------------------¢¢Press 'P' to toggle between PMG and playfield editing. An indicator¢just to the left of the Draw/Fill icon will turn on in PMG mode.¢¢The mode will default to an auto-select of whichever PMG object is¢under the current cursor location. Just press the fire button to¢draw/erase, or enter PMG commands, and they will automatically use the¢PMG at the cursor location, if one exists. Nothing will happen if¢there is no PMG object at that location.¢¢Specific PMG objects may be selected manually, by pressing the keys¢1-4 to select players 1-4, or 5-8 to select missles 1-4. Even though¢players are technically labeled from 0-3, I use 1-4 for ease in¢keyboard selection. Manual selection will become necessary if two¢PMGs overlap, because the auto-select routine will always take the¢lower number.¢¢Both solid and dithered fills react differently with PMG objects.¢There is no function to fill to graphic borders, and fill mode will¢simply copy the current line of a PMG object to the next line. Thus¢to fill a PMG, you will need to draw a line across the top of the PMG,¢press the spacebar to turn on fill mode, and then hold the fire button¢while pulling the joystick down. Dither mode operates in the same¢way, except that when dither patterns are detected, they are bit¢shifted to maintain the pattern. To create a dithered PMG, you will¢need to plot every other pixel on the top line of the PMG. Press the¢spacebar and the 'D' key, and then hold the fire button and stick down¢in the same manner as solid filling.¢¢PMG COMMANDS:¢-------------¢¢< > Change the current PMG's width.¢M Toggle the priority bit for missles being used as a 5th player.¢O Toggle the priority bit for overlapping PMG colors.¢F Toggle four modes of playfield and PMG priority order. This¢ changes which objects appear 'in Front' of other objects.¢¢POSITIONING PMGs:¢-----------------¢¢Shift 1-8 sets the horizontal position of the corresponding PMG to the¢cursor location. This operates a bit differently whether or not the¢cursor is located on the top scan line. There is a table that stores¢the starting attributes for all PMG registers. When the cursor is on¢the top scan line, any PMG changes will be made to this table, and all¢of the PMG attributes can be configured. When the cursor is partway¢down the screen, changes are made within the DLI routine which can¢only support one register change per line. In case of conflicts, GED¢will try to find free spots to make DLI register changes, but there¢are limits to what the program can do. This is explained more fully¢in the TECH.DOC file, and I suggest you study this if you want to get¢the most out of this potentially powerful ability.¢¢Another difference occurs when changing PMGs at the top of the screen.¢The missle objects have some auto-positioning logic to place¢themselves at optimum locations. When fifth player enable is turned¢off, missles will automatically be placed at the end of their¢corresponding players, allowing a slightly larger player object.¢Changes to the player's position or size will automatically relocate¢the missle to its proper place. With fifth player enabled, all of the¢missles will be placed one after another, adjusting for any changes in¢missle size. Shift-5, which sets the location of the first missle,¢will set the starting location of the fifth player. These¢auto-placements are only valid at the top of the screen. If you¢reposition PMGs in the middle of the screen, each missle must be moved¢individually -- even with fifth player enabled.¢¢BRUSHES:¢--------¢¢GED allows a limited form of brushes, that can copy data from a PMG¢object to the playfield. The implementation is simple, but can still¢be quite useful.¢¢Draw a shape in one of the PMG objects, and then move the cursor to¢the top of the shape and press the 'B' key. This will place the¢program in Brush mode, and anytime the joystick button is pressed, GED¢will copy the shape from the PMG object into the playfield at the¢cursor location, using the active color register. The first blank¢line encountered in the PMG object will mark the end of the brush.¢¢The drawing mode icon will be a round dot when in brush mode.¢¢Press 'B' again, or the space bar to return to regular drawing mode.¢¢COLOR PALETTE CONTROLS:¢-----------------------¢¢Breifly, since the color registers are stuffed multiple times per¢line, a change in the color palette will only effect a portion of the¢line which I call a color cell. To see a visual appearance of color¢cells, start from the empty GED screen and fill it with color register¢1. Then move down several lines and fill with color 2. Repeat with¢color 3. Then press the 'T' key to put up the test palette, and look¢at the screen. The color registers in the playfield data have not¢been changed, but multiple colors are being stuffed into them,¢creating vertical bands of color. Each different colored section of a¢line is what I call a color cell. It's a color register that is only¢displayed for part of the scan line. There are eight color cells per¢line, although you would have to plot all of the color registers on¢the same line in order to see all eight color cells on the same line.¢¢The TECH.DOC file has a more complete description of color cells. If¢you're lost, try and study that file and see if it makes any more¢sense. I'm always available to answer questions as well.¢¢With that out of the way, here's how you change colors.¢¢Shift-Arrows adjust the Hue+Intensity of the color cell at the cursor¢location.¢¢When PMG mode is active, the color of the currently selected PMG¢object will be changed. Changing PMG colors works a bit differently¢than the playfield colors. Since new colors are not stuffed¢automatically each line, PMG color changes will effect all lines from¢the cursor position to the bottom of the screen, or to any other place¢where the color was previously changed further down the screen.¢¢Playfield color changes only effect one scan line, so there needs to¢be an easy way to copy color palettes to additional lines. The 'C'¢key will copy the current color cell into the same position on the¢next line down. You can hold down the C key to repeat the effect.¢Use the C function when you are changing just one color, and don't¢want to change any of the other color cells.¢¢The 'W' key will copy the entire line of color cell palettes to the¢next line down. Use this function when you have changed all of the¢color registers, and want to copy the entire palette.¢¢The 'X' key allows you to exchange two playfield color registers. One¢register should be selected with the 0-3 keys, (or the G command).¢Then position the cursor on top of the color you wish to exchange¢with, and press X. The command will effect all of the screen below,¢and to the right of the cursor location. Also, the active color¢register will be exchanged as well. Since the pixel at the cursor¢location was swapped, having the active color changed too will allow¢you to press X a second time to toggle things back the way they were.¢¢COLOR CELL BOUNDARIES:¢----------------------¢¢GED now allows the locations of the color cell boundaries to be skewed¢left or right as a group. Normally, this is the first step to perform¢when coloring a picture, to best match color cell boundaries to the¢objects in the picture. This is a global screen setting only, and¢cannot be adjusted in mid-screen.¢¢The ',' and '.' keys skew the boundaries left or right.¢¢The 'T' key changes the screen to a test palette, which will make it¢easier to see the boundaries between the color cells. This is the¢best mode to be in when using the above skew control. Press T again¢to return to the normal screen palette.¢¢DISK I/O¢--------¢¢The compression protocol has not yet been implemented, but this will¢be included in a future release. Future GED versions will be able to¢load uncompressed pictures without problems.¢¢To get a disk directory, press Esc, and then a number from 1-9. The¢directory function also sets the current default drive. Filenames for¢loading & saving will use the default drive without having to type¢'Dn:'.¢¢L - Load graphic.¢S - Save graphic. This will prompt with the last loaded filename.¢ Press return to accept it, or edit the name and press return.¢¢GED will load DOS II binary files with the load function. This can be¢used to import GR.15 raw data, PMG data, or GED format color palettes.¢Although there is no method for saving individual components like this¢from within GED, these may be saved from DOS after exiting GED. Here¢are the memory addresses for the various components:¢¢$5330-$5AFF Color palette data¢$5B00-$5FFF PMG data¢$6000-$600F Picture header¢$6010-$7F4F 320x200 screen data¢¢COLORING HINTS:¢---------------¢¢The default priority mode in GED is to draw PMG objects behind the¢playfield. In this mode, PMGs will only be visable in sections of the¢picture that are cleared to background color. This often works out¢best, since you can make the players maximum width, and mask in front¢of them with other colors at full resolution. Note that when the¢missles are combined as a fifth player, this object appears in front¢of all playfield colors, regardless of the priority settings. I'm a¢bit confused by this, since the hardware manual appears to show that¢it should be possible to have its priority below the playfield. This¢is not the way it works in the real world though.¢¢Coloring pictures in GED can be an interesting process, because of all¢the potential choices for selecting which registers or objects will¢display which colors. The boundaries where the color register changes¢occur are staggered for each register. (See the TECH.DOC file for¢more information.) What this means, is that finding the optimum¢selection of color registers often requires a lot of juggling, and¢there are no rules that say a solid colored object will be drawn¢entirely with the same color register. As an object changes shape as¢it progesses down the screen, it may cross different color boundaries,¢making it advantageous to switch to a different color register. You¢would then change the palette of the new register to match, and the¢old register will be freed to use for something else.¢¢I will be uploading some tutorial pictures in the near future, to help¢you figure out how to make the best use of available registers. I just¢didn't have time to finish these for the initial release.¢¢OTHER SAMPLE PICTURES:¢----------------------¢¢The MARTIAN.GED picture was done with an early version of GED that did¢not support PMG objects. Even still, it has a good dispersion of¢colors for a playfield only picture, showing as much as 8 colors per¢line. I also really like the anti-aliased fonts.¢¢TEST.GED shows how many colors you can display on one line using the¢new mode. By including dithering, the bars at the top show 40 colors¢per line. The boxes at the bottom show a decent flesh tone color made¢by alternating scanlines of pink and orange. The box in the middle is¢formed from the colors of the other two. The greatest thing about¢this flesh color, is that it takes only one color register since there¢are no horizontal changes.¢¢GED UPDATE HISTORY:¢-------------------¢¢** v.1 **¢¢Initial release.¢¢** v.2 **¢¢New Features:¢¢Undo command for fill operations, using the 'U' key.¢¢The 'X' key allows you to exchange two playfield color registers. One¢register should be selected with the 0-3 keys, (or the G command).¢Then position the cursor on top of the color you wish to exchange¢with, and press X. The command will effect all of the screen below,¢and to the right of the cursor location. Also, the active color¢register will be exchanged as well. Since the pixel at the cursor¢location was swapped, having the active color changed too will allow¢you to press X a second time to toggle things back the way they were.¢¢Quick reference guide included as file GEDQUICK.DOC.¢¢Bug Fixes:¢¢Several internal operations did not adjust properly to different skew¢settings, causing the wrong color cells to be selected.¢¢The C command to copy colors did not work.¢¢The position of Missle #1 was not stable.¢¢Positions of missles 2-4 did not automatically adjust to changes in¢missle #1's position, when 5th player mode is enabled. (Note, auto-¢adjustment only occurs when position is changed on the top scan line).¢¢GED has a run address appended to the file, for non-Sparta users.¢Hopefully, I will continue to remember this in the future.¢¢KEEP IN TOUCH:¢--------------¢¢I'm always interested to receive feedback on GED, or anything else.¢¢John Harris¢45346 Graceway Dr.¢Ahwahnee, CA 93601¢¢jharris@cup.portal.com¢GEnie:JHARRIS32¢
