Background sync - GameCreators Forum

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KenMiller

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Joined: 16th May 2009

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Posted: 16th May 2009 15:30

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Hello,

Possibly an incredibly silly question, but I'm going to make it and risk the flames anyhoo

I'm waiting on the two handson volumes being delivered from amazon, so I've been learning through some tutorials online..
I've been putting this in to a crappy space invaders clone to try things out.

One thing I've noticed, is that whenever a bullet is fired, the background flashes, as though its resyncing the background. I'm gathering this is because I have 'paste image 2,0,0 actually inside the main game loop, but when I move this to just before the do, it well, refuses to show it

Any help would possibly save both my head and my desk.

Cheers,

+ Code Snippet

cls rgb (0,0,0)
xaxis = 320
sync off
load image "background.bmp",2
load image "player.bmp",1
load image "bullet.bmp",3
do
paste image 2,0,0
sprite 1,xaxis,400,1
if leftkey() = 1 then xaxis = xaxis - 1
if rightkey() = 1 then xaxis = xaxis + 1
if xaxis<0 then xaxis=0
if xaxis>580 then xaxis=580
If Spacekey()=1 Then Gosub MoveBullet
loop

MoveBullet:
BulletPosX = xaxis + 20
  BulletPosY = 400-16
  For N=BulletPosY To 0 Step -1
paste image 2,0,0
sprite 3,BulletPosX,N,3
sync
  Next N
Return

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bobbel

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Joined: 5th Jan 2009

Location: In my DBPro case xD

Posted: 16th May 2009 15:52

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can you try this? not sure if it helps thought

+ Code Snippet

cls rgb (0,0,0)
xaxis = 320
sync off
load image "background.bmp",2
load image "player.bmp",1
load image "bullet.bmp",3
do
paste image 2,0,0
sprite 1,xaxis,400,1
if leftkey() = 1 then xaxis = xaxis - 1
if rightkey() = 1 then xaxis = xaxis + 1
if xaxis<0 then xaxis=0
if xaxis>580 then xaxis=580
If Spacekey()=1 Then Gosub MoveBullet
sync
loop

MoveBullet:
BulletPosX = xaxis + 20
  BulletPosY = 400-16
  For N=BulletPosY To 0 Step -1
sprite 3,BulletPosX,N,3
  Next N
Return

(\__/)
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(> < ) This is Bunny. Copy Bunny into your signature to help him on his way to world domination!

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KenMiller

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Joined: 16th May 2009

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Posted: 16th May 2009 16:04

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It constantly syncs. ;/
I've found the best place to have the sync is after the For N=BulletPosY To 0 Step -1

But even then, the screen turns blue and the background disappears while the bullet is firing

Ah well, Not a biggy, I'm sure I'll work it out while working through the hands on guides once amazon sends them

Thanks,

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IanM

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Joined: 11th Sep 2002

Location: In my moon base

Posted: 16th May 2009 16:40

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Replace that SYNC OFF with a SYNC ON in bobbel's code. You'll also need to remove that loop, and instead move the bullet one step at a time every loop of the main loop.

Something like this:

+ Code Snippet

sync on

cls rgb (0,0,0)
xaxis = 320

load image "background.bmp",2
load image "player.bmp",1
load image "bullet.bmp",3

BulletFired = 0

do
   paste image 2,0,0
   sprite 1,xaxis,400,1
   if leftkey() = 1 and xaxis > 0 then xaxis = xaxis - 1
   if rightkey() = 1 and xaxis < 580 then xaxis = xaxis + 1

   If Spacekey()=1 and BulletFired = 0 Then Gosub StartBullet
   if BulletFired = 1 then Gosub MoveBullet
   sync
loop

StartBullet:
   BulletPosX = xaxis + 20
   BulletPosY = 400 - 16
   BulletFired = 1
   sprite 3, BulletPosX, BulletPosY, 3
   return

MoveBullet:
   BulletPosY = BulletPosY - 1
   if BulletPosY < 0
      BulletFired = 0
      delete sprite 3
   else
      sprite 3, BulletPosX, BulletPosY, 3
   endif
   return

Utility plug-ins collection (updated 28/03/09) and
http://www.matrix1.demon.co.uk

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KenMiller

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Joined: 16th May 2009

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Posted: 16th May 2009 18:15

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Ah, that did it, and it makes sense

Thanks a lot.

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