No Fragments Archive 10: Diskmags/nf_archive_10.iso/MAGS/POWERMAG/POWER16.MSA/POWER_16/MISSMAKE.PWR

Text File | 1985-11-20 | 12KB | 257 lines

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                     THE MISSING LINK MAKE PROGRAM

                           ARTICLE BY DEANO
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   The  missing link doc file talks about different kinds of  banks  for
   things such as bobs,  joeys,  blocks,  etc.  But how do we make those
   banks in the first place?  The answer is simple.  On the missing link
   disk is a file called MAKE.BAS. Note that only so much source appears
   with  the giveaway version of the package like this file,  so if  you
   have'nt registered then this file may be stored in PRG format on your
   copy of the package. Anyway let's have a look into it shall we?

   As  you may or may not know.....the missing link uses a new  type  of
   sprites known as bobs.  This are actually called pre-shifted sprites.
   The normal STOS sprites work like this......in order to get past  the
   problem of the ST's sixteen pixel boundary the sprite has to be  pre-
   shifted.  This means so many copies of the sprite have to be made and
   each  one  is  scrolled by one pixel to the  right  until  there  are
   sixteen copies of one sprite image made before it goes on screen.

   This  all has to be done before the sprite can be moved or placed  on
   screen in order to postion it anywhere on screen.  This takes a  fair
   bit of processor time which explains why sprites are often jerky  and
   slow. So the routine goes....make sixteen copies, place it on screen,
   make another sixteen copies, place it on screen at the next pixel and
   so on. But there is a better faster way of doing this.

   The difference with STOS sprites and pre-shifted sprites is that pre-
   shifted  sprites are pre-shifted once and held in memory whilst  STOS
   sprites  are pre-shifted as they move across screen which means  they
   take up less memory than pre-shifted sprites.

   Even  though  STOS sprites make sixteen images of themselves  we  can
   actually decided how many images of pre-shifted sprites are made.  We
   can make either 16,  8,  4,  2, or 1 image. Might you the less images
   you  use the more they jerk when moved.  This can be fixed by  moving
   them at different steps.  So we need to calculate how many pixels  to
   move  an image.  So if we wanted our sprite to move in steps  of  one
   pixel  we  would need to make sixteen images,  one for  each  of  the
   sixteen pixels of the boundary. This is worked out like this.

   16/1=16

   So we want to move the sprite at one pixel at a time so we divide  it
   by sixteen and we get the answer sixteen.  This means we have to make
   sixteen images of the sprite in order for it to be moved by one pixel
   at a time. Now lets suppose we wanted to move it by two pixels.

   16/2=8

   This  has now halved the size of the image because we're  now  moving
   the image at two pixels at a time so only halve of the images have to
   be made. Look at these other examples.

   16/4=4 : Move sprite at 4 pixels so make 4 images of each sprite.

   16/8=2 : Move sprite at 8 pixels so make 2 images of each sprite.

   So all we are doing is simply taking the number of pixels we want the
   sprite  to  scroll and dividing it by sixteen to found out  how  many
   images  we need to make.  Note that if your sprite is to move up  and
   down  the  screen  only then we only need to make one  image  as  the
   sixteen pixel boundary only applies to moving across the screen.

   But how do we make these images in the first place?  Well thats where
   the  MAKE program comes in.  First load it up and you  are  presented
   with  menus  covering  different convert  options.  The  one  we  are
   interested in at the moment is the one to convert our STOS sprites to
   pre-shifted sprites...in other words bobs.  From the LOAD menu  click
   on SPRITES and load your sprites.  Next go to the MAKE menu and click
   on MAKE BOBS. Here we see three options.

   MAKE BOBS

   IMAGES

   QUIT

   Before we convert the sprites to bobs we need to choose the number of
   images  we need of each one,  so postion the mouse pointer  over  the
   word  IMAGES and press the left mouse button.  You will now  see  the
   word  IMAGES with a number next to it and the word SPRITE above  that
   with its image number next to it.  Move the mouse pointer over either
   word  and click on either mouse key.  Notice how the left  and  right
   mouse buttons step through each number of each option.

   Select  sprite  one  and image four by clicking on  SPRITE  till  its
   number  says 1 and on IMAGES till it says 4.  This means we have  set
   MAKE  to make four images of sprite one.  If we wanted to  make  four
   images  of  all the sprites then we can simply click on  IMAGES  with
   both  mouse  buttons.  Note that if we now step through  the  sprites
   we see they are all set to be converted to four images each.

   Now  all  the images are set we can proceed to make them  into  bobs.
   Click on EXIT from the IMAGE selection screen and click on MAKE  BOBS
   to  start  the pre-shifting.  Note how MAKE shows  the  sprites  pre-
   shifting on screen while its doing it.  How long it takes depends  on
   how many images are being pre-shifted.

   When  the program stops,  click on EXIT to go back to the main  menu.
   Our  sprites are now converted to bobs and all we have to do  now  is
   save them. From the SAVE menu click on BOBS and save them under their
   new name making sure the extension is .MBK.

   EG:- BOBS.MBK

   Its  important to remember that the more images made of  each  sprite
   the bigger the bank is so make sure theres enough room on  disk.  The
   MAKE program has just turned the sprite bank into a bob bank for  use
   with the bob commands. We can now use these bobs in a routine.

   10 key off : flash off : hide on : curs off : mode 0
   20 rem ~~ First load the bob bank into memory bank 5
   30 load "bobs.mbk",5
   40 rem ~~ Place bob one on screen and move it along by 4 pixels
   50 logic=back : XBOB=10 : YBOB=100
   60 repeat
   70 wash logic,XBOB-10,YBOB-10,XBOB,YBOB
   80 bob logic,start(5),0,XBOB,YBOB,0
   90 screen swap : wait vbl
   100 XBOB=XBOB+4 : until XBOB>300

   This  routine loads our BOB bank into bank five and the rest  of  the
   routine zooms it across the screen, see how fast and smooth it moves?
   Notice also that unlike sprites the bobs can be placed into any  bank
   and they can either be loaded in every time the routine is run or  it
   can  be left in there without loading all the time.  The  reason  for
   WASH  and SCREEN SWAP is because unlike sprites the bobs don't  clear
   the  trail  behind them.  Notice also that WASH is set to  clear  ten
   pixels behind and over the sprite to ensure no trails are left.

   In  the  future I plan to do an article on moving and  animating  the
   bobs so watch out for that.

   Back  to  the  MAKE program.....we have  other  options  which  we'll
   discuss in turn.

   JOEYS

   The  method  for joeys are just the same as  bobs,  just  follow  the
   method for bobs to convert sprites to joeys.

   WORLD BLOCKS

   This  option will convert our sprites to world blocks so they can  be
   used by the world command. Same method as converting sprites to bobs.

   LANDSCAPE BLOCKS

   This  option  is  the  same as creating world  blocks  only  that  it
   converts  sprites  to  landscape blocks for use  with  the  landscape
   command.  Note that theres no IMAGES option for this option,  this is
   because  landscape only moves its blocks up and down the  screen  and
   the  sixteen pixel boundary does'nt exist here so theres no need  for
   pre-shifting. Just click on MAKE BLOCKS and save them.

   TILES

   Used by the tile and moziac commands.  This option works the same  as
   the bob option only that it creates tiles.

   Note  that these last four options all need to be saved with the  MBK
   extension,  like  BOBS they are converted into special banks so  they
   can be used by their commands. They are loaded in same way as bobs.

   PICTURE

   This option makes up a picture of your sprites, to active it you must
   first load the sprites then from the MAKE menu click on PICTURE,  the
   program will then place your sprites on screen in order one after the
   other  and  make up a picture.  You can then save  the  picture.  The
   sprites must be 16x16 in size.

   DIGIBANK

   Normally you can play a sample using the digiplay command but  should
   you be used to using STOS maestro then you may want to put a load  of
   samples into one bank then this is where this option comes  in.  Lets
   look at each option,  first from the MAKE menu click on DIGIBANK  and
   you'll  be  presented with a new options screen.  Note that  you  can
   either select a number or click on the option.

   LOAD SAMPLE

   Allows you to load a sample into the bank.

   SAVE SAMPLE

   Unlike  STOS maestro's accessory,  this option allows you to  save  a
   sample out of the bank and on disk as a stand alone sample.

   LOAD DIGIBANK

   When  you've saved a bank of samples,  it becomes a digibank  so  the
   digiplay  command can understand it.  This option allows you to  load
   the previously saved bank for editing.

   SAVE DIGIBANK

   Saves out a digibank for use with the command.

   CLEAR DIGIBANK

   Clears the digibank in memory, all samples are lost.

   PLAY SAMPLE

   Choosing  this option will take you to another  screen,  postion  the
   mouse  over the number and press either mouse key to  step  backwards
   and  forwards through the samples in memory.  To play it press  space
   and enter the speed.  Press space to play it and the sample will play
   in a loop. Press space again for the main menu.

   (UN)SIGN SAMPLE

   This  option will take you to the play screen.  From here select  the
   sample you wish to sign/unsign and press space for the main menu.

   EXIT

   Guess what........takes you back to the main menu.

   Once you've created your digibank and saved it you can play it  using
   the digiplay command like this.....

   digiplay 1,start(5),SAMPLE,10,1

   The parameter SAMPLE is normally used for the length of a raw sample.
   In this case it ranges from 0 to 49.  If the size is less than  fifty
   then  the  parameter SAMPLE is used for the number of the  sample  to
   play between 0 and 49. If SAMPLE equals more than 49 then the data in
   bank  five is assumed to be a raw sample but if its less  than  fifty
   then its assumed to be a digibank......examples.

   PLAY A RAW SAMPLE AT SPEED 10

   digiplay 1,start(5),32000,10,1

   PLAY A SAMPLE FROM A DIGIBANK AT SPEED 10

   digiplay 1,start(5),4,10,1

   In  order to put a digibank in a memory bank then just like  all  the
   other  new  created banks we save it as MBK and load it as  we  would
   load any MBK file.

   Well  thats  it for this article,  I will be doing one  on  the  EDDY
   program  soon so hopefully with that and this article you'll be  able
   to get creating some games with the missing link extension.

   This is Deano signing off.......(Ending nicked from Tony)