Text Only | Text with Attachments

QB64.org Forum

Active Forums => QB64 Discussion => Topic started by: 40wattstudio on February 24, 2020, 02:04:59 pm

Title: Increase array with spacebar? [Solved]
Post by: 40wattstudio on February 24, 2020, 02:04:59 pm
Hi everyone!

I'm new to this forum but not to Qbasic. That being said, there's been something that I've been trying to figure out for a while now and haven't made much progress.

Basically, I'm trying to make a traditional top-down shooter where the spacebar is the fire key.
I can make the spacebar fire one unique shot, but what I can't for the life of me figure out is how to get it to fire X amount of *unique* shots. (By unique I mean that each shot has its own Y coordinate so it can be tracked separately for the hit detection).

The way I understand it is like this:
When the player hasn't done anything (like pressed the spacebar to fire a shot), the array used to hold the shots is empty or 0 because nothing has happened. Then when the player presses or holds down the spacebar, the array should increase by 1, generating new coordinates for each unique shot.

Is it possible to start with an empty array and increase by one? Or am I going about this the wrong way entirely?

Title: Re: Increase array with spacebar?
Post by: FellippeHeitor on February 24, 2020, 02:20:33 pm
Hello 40wattstudio and welcome to the forum.

You're looking for REDIM. You can start an empty array:

Code: QB64: [Select]
  1. REDIM myarray(0) AS LONG

then you can increase it as needed:

Code: QB64: [Select]
  1. REDIM _PRESERVE myarray(UBOUND(myarray) + 1) AS LONG

Beware the the increase/decrease of an array is a memory consuming task, so it's better to increase it by a larger amount, when needed:

Code: QB64: [Select]
  1. REDIM _PRESERVE myarray(UBOUND(myarray) + 100) AS LONG

Maybe you'd be better off with a large array at start, but with an index to track which items have been used, this way you won't have to REDIM it as often.

Click the keywords in the code boxes above to jump the the wiki article on them.
Title: Re: Increase array with spacebar?
Post by: 40wattstudio on February 24, 2020, 02:46:07 pm
Hi Fellippe, thanks for the quick response!

I had tried the REDIM before, but that was my very first time using it so I was probably missing something. I definitely don't remember using 2 sets of () in the redimmed array.

It sounds like REDIM can be used inside a subroutine, but can the newly dimensioned array be identified by other subs?
For example, I have  a "hitdetection" sub that needs to cycle through the array of newly generated shots created by the "fireshot" sub.
Title: Re: Increase array with spacebar?
Post by: FellippeHeitor on February 24, 2020, 02:54:14 pm
You can REDIM SHARED in the main module, so the array will be visible across subs and functions.
Title: Re: Increase array with spacebar?
Post by: bplus on February 24, 2020, 03:10:30 pm
Hi 40 watts,

You could limit the amount of bullets to nBullets and just track if they are active of not.
When you press spacebar the code scans for nonactive bullet and activates it.
Deactivate bullets as they hit something or leave the screen.

Do you know about TYPE's?

You can setup a Bullet Type and track all you need to know about each

Code: QB64: [Select]
  1. TYPE bullet
  2.     x AS INTEGER
  3.     y AS INTEGER
  4.     dx AS SINGLE 'change along x-axis
  5.     dy AS SINGLE 'change along y axis
  6.     active AS INTEGER ' 0 false, -1 or track how long active
  8.  
  9. Dim shared nBullets = 10  'or make constant
  10.  
  11. DIM SHARED Bullets(1 TO nBullets) AS bullet
  12.  
  13. FOR i = 1 TO nBullets
  14.     'bullets(i).x, bullets(i).y  >>> bullet position  for drawing it
  15.     Bullets(i).x = Bullets(i).x + Bullets(i).dx 'update position on x axis
  16.  
  17.     IF Bullets(i).x < 0 THEN 'bullet off screen deactivate
  18.         Bullets(i).active = 0
  19.     END IF
  20.     'and so on...
  22.  

If all bullets are active when you press spacebar, hear click sound because you just fired a blank ;-))
Title: Re: Increase array with spacebar?
Post by: Petr on February 24, 2020, 03:18:50 pm
My version - in text mode, for maximal 23 bullets.

Code: QB64: [Select]
  1. 'shoot demo - press spacebar for shoot.
  2.  
  3. TYPE fire
  4.     x AS INTEGER
  5.     y AS INTEGER
  7.  
  8. REDIM fire(1 TO 23) AS fire '23 rows
  9.  
  11. x = _WIDTH / 2
  12. y = 0
  13.  
  14.  
  16.     CLS
  17.     WHILE _KEYDOWN(32)
  18.         s = 1
  19.         DO UNTIL fire(s).y = 0 OR s > 22: s = s + 1: LOOP
  20.         fire(s).y = 1
  21.         EXIT WHILE
  22.     WEND
  23.  
  24.     FOR s = 1 TO 23
  25.         IF fire(s).y THEN
  26.             fire(s).y = fire(s).y + 1
  27.             IF fire(s).y > 23 THEN fire(s).y = 0
  28.             IF fire(s).y THEN LOCATE fire(s).y, x: PRINT "*"
  29.         END IF
  30.     NEXT
  31.     _LIMIT 25
  33.  

Press (and try hold) spacebar.
Title: Re: Increase array with spacebar?
Post by: 40wattstudio on February 24, 2020, 03:34:01 pm
Hi bplus and Petr,

Definitely some good suggestions there!

I've been using TYPE's like crazy after I learned how to use them in a School Freeware Qbasic tutorial series.

I'll let you know how it turns out after I get a chance to play around with the code examples.
Thanks!
Title: Re: Increase array with spacebar?
Post by: TerryRitchie on February 25, 2020, 01:41:35 am
You don't need to use REDIM to keep track of bullets. Below is a crude demo showing how you can keep track of 5 bullets on the screen. Change the CONST MAXBULLETS = line to 10 or 15 and control more bullets.

Code: QB64: [Select]
  1. CONST FALSE = 0, TRUE = NOT FALSE
  2.  
  3. CONST MAXBULLETS = 5
  4.  
  5. TYPE BULLET
  6.     x AS INTEGER '        X location of bullet
  7.     y AS INTEGER '        Y location of bullet
  8.     active AS _BYTE '     TRUE if bullet currently ascending
  10.  
  11. DIM ShipX AS INTEGER '    X location of ship
  12. DIM shot AS INTEGER '     bullet counter
  13. DIM KeyWait AS INTEGER '  time to wait between shots fired
  14.  
  15. DIM Bullet(MAXBULLETS - 1) AS BULLET ' bullets
  16.  
  17. SCREEN _NEWIMAGE(640, 480, 32) '                                        create window
  19. ShipX = 319 '                                                           X start location of ship (center)
  20.  
  21. DO '                                                                    main loop
  22.     _LIMIT 60 '                                                         60 frames per second
  23.     CLS
  24.     PRINT '                                                             print instructions
  25.     PRINT " RIGHT/LEFT ARROW KEYS TO MOVE"
  26.     PRINT " SPACEBAR TO FIRE"
  27.     PRINT " ESC TO EXIT"
  28.     shot = 0
  29.     DO '                                                                cycle through all 5 bullets
  30.         IF Bullet(shot).active THEN '                                   is this bullet active?
  31.             Bullet(shot).y = Bullet(shot).y - 5 '                       yes, decrement Y location
  32.             IF Bullet(shot).y < 0 THEN '                                leave top of screen?
  33.                 Bullet(shot).active = FALSE '                           yes, this bullet no longer active
  34.             ELSE '                                                      no, bullet still on screen
  35.                 LINE (Bullet(shot).x - 2, Bullet(shot).y)-(Bullet(shot).x + 2, Bullet(shot).y + 4), _RGB32(0, 255, 0), BF
  36.             END IF
  37.         END IF
  38.         shot = shot + 1
  39.     LOOP UNTIL shot = MAXBULLETS
  40.     IF _KEYDOWN(19200) THEN '                                           LEFT ARROW key?
  41.         ShipX = ShipX - 2 '                                             yes, move ship to left
  42.         IF ShipX < 20 THEN ShipX = 20 '                                 stop motion if too far
  43.     END IF
  44.     IF _KEYDOWN(19712) THEN '                                           RIGHT ARROW key?
  45.         ShipX = ShipX + 2 '                                             yes, move ship to right
  46.         IF ShipX > 620 THEN ShipX = 620 '                               stop motion if too far
  47.     END IF
  48.     IF _KEYDOWN(32) AND KeyWait = 0 THEN '                              SPACEBAR pressed and wait timer exhausted?
  49.         shot = 0
  50.         DO '                                                            yes, cycle through all 5 bullets
  51.             IF NOT Bullet(shot).active THEN '                           is this bullet active?
  52.                 Bullet(shot).active = TRUE '                            no, it is now
  53.                 Bullet(shot).x = ShipX '                                set X location of bullet
  54.                 Bullet(shot).y = 453 '                                  set Y location of bullet
  55.                 KeyWait = 5 '                                           wait 5 frames until next shot allowed
  56.                 EXIT DO
  57.             END IF
  58.             shot = shot + 1
  59.         LOOP UNTIL shot = MAXBULLETS
  60.     END IF
  61.     IF KeyWait THEN KeyWait = KeyWait - 1 '                             decrement key wait counter
  62.     LINE (ShipX - 20, 455)-(ShipX + 20, 475), _RGB32(0, 255, 0), BF '   draw ship
  63.     LINE (ShipX - 2, 450)-(ShipX + 2, 454), _RGB32(0, 255, 0), BF '     draw gun stack
  64.     _DISPLAY '                                                          update window with changes
  65. LOOP UNTIL _KEYDOWN(27) '                                               leave when ESC pressed
Title: Re: Increase array with spacebar?
Post by: MasterGy on February 25, 2020, 03:18:58 am
I also made a version, I want to show the importance of systematization. be a large array and have lots of indexes, you can give infinite properties to 1 actor later. it is important to say from experience that the way i made the poppy game was that it was easy to add different features per character.

A,D move, SPACE shot

Code: QB64: [Select]
  1. maxballs = 999
  2. DIM balls(maxballs - 1, 5): 'big array, unnecessary save memory, it is worth listing all the characteristics of 1 bullet per index
  3. '0-active
  4. '1-X position
  5. '2-Y position
  6. '3-color
  7. '4-speed
  8. '5-letter-character
  9.  
  10. sc = _NEWIMAGE(640, 480, 32): SCREEN sc
  11.  
  12. meX = 40: meY = 1 'my coordinates
  13. shotspeed_rate = 1 'universal shotspeed rate
  14. randshotspeed = 1 '0=same shot speed 1=different shot speed
  15.  
  16. REM ----------------------------------------------------------------------
  17.  
  19.     IF _KEYDOWN(100) THEN meX = meX + 1 'move left
  20.     IF _KEYDOWN(97) THEN meX = meX - 1 'move right
  21.     IF _KEYDOWN(32) THEN GOSUB createnewshot 'create new shot
  22.  
  23.     IF meX < 1 THEN meX = 1
  24.     IF meX > 79 THEN meX = 80
  25.     GOSUB shotmanager 'calculating balls coordinates
  26.  
  27.     CLS: LOCATE meY, meX: PRINT "X"; 'draw me
  28.     FOR actualindex = 0 TO maxballs - 1 'draw balls
  29.         IF balls(actualindex, 0) THEN 'draw ball ,if active
  30.             LOCATE balls(actualindex, 2), balls(actualindex, 1) 'set coordinates
  31.             COLOR balls(actualindex, 3) 'set color
  32.             PRINT CHR$(balls(actualindex, 5)) 'draw character
  33.         END IF
  34.     NEXT actualindex
  35.  
  37.  
  38. createnewshot:
  39. FOR freeindex = 0 TO maxballs - 1
  40.     IF balls(freeindex, 0) = 0 THEN GOTO findfreeindex
  41. NEXT freeindex: RETURN 'no free index, no new shot
  42. findfreeindex: 'free area index is 'index'
  43. balls(freeindex, 0) = 1 'index is active
  44. balls(freeindex, 1) = meX 'set X position is ME position
  45. balls(freeindex, 2) = 2 'set start Y position
  46. balls(freeindex, 3) = _RGB32(256 * RND, 256 * RND, 256 * RND)
  47. balls(freeindex, 4) = 1 + randshotspeed * RND(1)
  48. balls(freeindex, 5) = 65 + INT(27 * RND(1))
  50.  
  51. shotmanager:
  52. FOR actualindex = 0 TO maxballs - 1
  53.     IF balls(actualindex, 0) THEN 'move shot when activated
  54.         balls(actualindex, 2) = balls(actualindex, 2) + balls(actualindex, 4) * shotspeed_rate 'move ball own speed
  55.         IF balls(actualindex, 2) > 29 THEN balls(actualindex, 0) = 0 'deactived if way end
  56.     END IF
  57. NEXT actualindex
  59.  
  60.  
  61.  
  62.  
  63.  
Title: Re: Increase array with spacebar?
Post by: 40wattstudio on February 25, 2020, 07:24:27 pm
Finally got to try out the different sample programs this afternoon. Wow, there sure are a lot of creative ways to do the same basic effect!
Petr: I like the simplicity of yours. Looks very good for Screen 0!
TerryRitchie: Yours was closest to what I needed (having your shots relative to a player ship definitely helped!)
MasterGy: Ah ha! So that's how they make those Matrix screensavers!

Here's what I came up with after I integrated everything:
Code: QB64: [Select]
  1. CONST FALSE = 0, TRUE = NOT FALSE
  2. CONST maxshots = 20
  3.  
  4. TYPE PLAYER
  5.     PIC AS LONG
  6.     HEIGHT AS INTEGER
  8.     MIDX AS INTEGER
  9.     MIDY AS INTEGER
  10.     X AS INTEGER
  11.     Y AS INTEGER
  12.     SPEED AS INTEGER
  14.  
  16.     PIC AS LONG
  18.     HEIGHT AS INTEGER
  19.     COLORS AS INTEGER
  20.     MIDX AS INTEGER
  21.     MIDY AS INTEGER
  22.     TOP AS INTEGER
  23.     BOTTOM AS INTEGER
  24.     RIGHT AS INTEGER
  25.     LEFT AS INTEGER
  27.  
  28. TYPE SHOT
  29.     PIC AS LONG
  30.     HEIGHT AS INTEGER
  32.     MIDX AS INTEGER
  33.     MIDY AS INTEGER
  34.     X AS INTEGER
  35.     Y AS INTEGER
  36.     SPEED AS INTEGER
  37.     ACTIVE AS _BYTE
  39.  
  40. DIM SHARED numshots AS INTEGER
  41. DIM SHARED keydelay AS INTEGER
  42. DIM SHARED shot(maxshots - 1) AS SHOT
  43. DIM SHARED player AS PLAYER
  45.  
  46. '                                                            ==== START HERE ===
  47. newscreen
  49.     IF _KEYDOWN(32) THEN '  - SPACEBAR
  50.  
  51.         basicsettings
  52.         level1
  53.  
  54.     END IF
  57.  
  58. SUB basicsettings '========================================================SUB BASIC SETTINGS
  59.  
  60.     win.MIDX = win.WIDTH / 2
  61.     win.MIDY = win.HEIGHT / 2
  62.     win.TOP = 0
  63.     win.BOTTOM = win.HEIGHT
  64.     win.LEFT = 0
  65.     win.RIGHT = win.WIDTH
  66.  
  67.     player.PIC = _LOADIMAGE("SCRAPSHIP\gfx\playerTEST.png") 'Add path to PNG file here. This is one is 60x60
  68.     player.WIDTH = 60
  69.     player.HEIGHT = 60
  70.     player.MIDX = player.WIDTH / 2
  71.     player.MIDY = player.HEIGHT / 2
  72.     player.X = win.MIDX - player.MIDX
  73.     player.Y = win.MIDY - player.MIDY
  74.     player.SPEED = 2
  75.  
  77.  
  78. SUB level1 '=============================================================SUB LEVEL 1
  79.  
  80.     newscreen
  81.     DO
  82.         PCOPY _DISPLAY, 1
  83.         moveplayer
  84.         fireshot
  85.  
  86.         _DISPLAY
  87.         PCOPY 1, _DISPLAY
  88.     LOOP UNTIL _KEYDOWN(27)
  89.     SYSTEM
  90.  
  92.  
  93. SUB fireshot '======================================================== SUB SET SHOT
  94.  
  95.     numshots = 0
  96.     DO
  97.         IF shot(numshots).ACTIVE THEN
  98.             shot(numshots).PIC = _LOADIMAGE("SCRAPSHIP\gfx\shot.png") 'Add path to PNG file here. This one is 10x20
  99.             shot(numshots).SPEED = 5
  100.             shot(numshots).HEIGHT = 20
  101.             shot(numshots).WIDTH = 10
  102.             shot(numshots).MIDX = shot(numshots).WIDTH / 2
  103.             shot(numshots).MIDY = shot(numshots).HEIGHT / 2
  104.             shot(numshots).Y = shot(numshots).Y - 5
  105.             IF shot(numshots).Y < 0 THEN
  106.                 shot(numshots).ACTIVE = FALSE
  107.             ELSE
  108.                 _PUTIMAGE (shot(numshots).X, shot(numshots).Y), shot(numshots).PIC
  109.             END IF
  110.         END IF
  111.         numshots = numshots + 1
  112.     LOOP UNTIL numshots = maxshots
  113.  
  114.     IF _KEYDOWN(32) AND keydelay = 0 THEN
  115.         numshots = 0
  116.         DO
  117.             IF NOT shot(numshots).ACTIVE THEN
  118.                 shot(numshots).ACTIVE = TRUE
  119.                 shot(numshots).X = player.X + player.MIDX - shot(numshots).MIDX
  120.                 shot(numshots).Y = player.Y
  121.                 keydelay = 10
  122.                 EXIT DO
  123.             END IF
  124.             numshots = numshots + 1
  125.         LOOP UNTIL numshots = maxshots
  126.     END IF
  127.     IF keydelay THEN keydelay = keydelay - 1
  128.  
  130.  
  131. SUB moveplayer '===========================================================SUB MOVE PLAYER
  132.  
  133.     IF _KEYDOWN(CVI(CHR$(0) + "K")) AND player.X > win.LEFT THEN '    - MOVE LEFT
  134.         player.X = player.X - player.SPEED
  135.     END IF
  136.  
  137.     IF _KEYDOWN(CVI(CHR$(0) + "M")) AND player.X + player.WIDTH < win.RIGHT THEN '  - MOVE RIGHT
  138.         player.X = player.X + player.SPEED
  139.     END IF
  140.  
  141.     IF _KEYDOWN(CVI(CHR$(0) + "H")) AND player.Y > win.TOP THEN '  - MOVE UP
  142.         player.Y = player.Y - player.SPEED
  143.     END IF
  144.  
  145.     IF _KEYDOWN(CVI(CHR$(0) + "P")) AND player.Y + player.HEIGHT < win.BOTTOM THEN '   - MOVE DOWN
  146.         player.Y = player.Y + player.SPEED
  147.     END IF
  148.  
  149.     _PUTIMAGE (player.X, player.Y), player.PIC
  150.  
  152.  
  153. SUB newscreen '==============================================================SUB NEW SCREEN
  154.     CLS
  155.     win.WIDTH = 1080
  156.     win.HEIGHT = 1080
  157.     win.COLORS = 32
  158.     SCREEN _NEWIMAGE(win.WIDTH, win.HEIGHT, win.COLORS)
  160.  
Text Only | Text with Attachments