Implementing boundary on player movement

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Adam_db

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Joined: 28th Feb 2007

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Posted: 28th Feb 2007 22:51

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Hey hey, im making a 2d space shooter in dbpro, and need help implementing some boundaries on my player movement code. very simple stuff, but i cant seem to get this to work right.

it stays within the boundaries of the screen, but gets stuck on the axis. my ship sprite is 50x92 in dimensions also.

anyway, heres my code.

+ Code Snippet


set display mode 800, 600, 32
load image "Ship.bmp" 1
color backdrop 0

PlayerPositionX = 400`sets initial x position
PlayerPositionY = 300`sets initial y position
PlayerSpeed = 3

sprite 1, PlayerPositionX, PlayerPositionY, 1

do
Gosub PlayerMovement
loop

PlayerMovement:

PlayerPositionX = sprite x(1)`check x coord of ship
PlayerPositionY = sprite y(1)`check y coord of ship

if downkey() = 1 and PlayerPositionY =< screen height() - sprite height(1)
    inc PlayerPositionY, PlayerSpeed
endif

if upkey() = 1 and PlayerPositionY +< screen height() - sprite height(1)
    dec PlayerPositionY, PlayerSpeed
endif

sprite 1, PlayerPositionX, PlayerPositionY, 1`reposition the sprite

return

any help would be welcome
thanks,
Adam

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Adam_db

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Joined: 28th Feb 2007

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Posted: 28th Feb 2007 23:36

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***********************
FIXED
***********************

Nevermind, fixed it. silly really.

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Sixty Squares

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Joined: 7th Jun 2006

Location: Somewhere in the world

Posted: 28th Feb 2007 23:58 Edited at: 28th Feb 2007 23:59

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Hello! I fixed it. This system is my favorite to use because no matter what you do the ship will never leave the screen (on the Y axis). Basically it just says that if the ship goes outside the screen, then just put it on the edge. See if you can figure out how to do the same for the X axis.

Anyway, here's your updated code:

+ Code Snippet


set display mode 800, 600, 32
load image "Ship.bmp" 1

color backdrop 0

PlayerPositionX = 400`sets initial x position
PlayerPositionY = 300`sets initial y position
PlayerSpeed = 3

sprite 1, PlayerPositionX, PlayerPositionY, 1

do
Gosub PlayerMovement
loop

PlayerMovement:

PlayerPositionX = sprite x(1)`check x coord of ship
PlayerPositionY = sprite y(1)`check y coord of ship

if downkey() = 1
    inc PlayerPositionY, PlayerSpeed
endif

if upkey() = 1
    dec PlayerPositionY, PlayerSpeed
endif




rem If the player is going to go outside the screen, then put it right on the edge.

rem If it goes farther than the bottom, then put it on the bottom.
if PlayerPositionY > Screen Height() - Sprite Height(1)
PlayerPositionY = Screen Height() - Sprite Height(1)
endif

rem if it goes higher than the top, then put it on the top.
if PlayerPositionY < 0
PlayerPositionY = 0
endif



sprite 1, PlayerPositionX, PlayerPositionY, 1`reposition the sprite

return

If you couldn't get it to work for the X axis, here's the code for it:

+ Code Snippet

rem If it goes farther than the right side, then put it on the right edge.
if PlayerPositionX > Screen Width() - Sprite Width(1)
PlayerPositionX=Screen Width() - Sprite Width(1)
endif

rem 0 is the left side of the screen.
if PlayerPositionX < 0
PlayerPositionX = 0
endif

Hope this helped

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Adam_db

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Joined: 28th Feb 2007

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Posted: 1st Mar 2007 14:24

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Thanks very much for posting Sixty Squares, I managed it myself, i have only just registered on the forums, so they need to check my posts are okay before i can respond.

Its interesting that you found a solution completely different to the one i came up with, its funny that no-ones codes the same thing, the same way dontcha think?

incidentally this is how i solved the problem, in case anyone else out there found it tricky, and wants another solution, i changed the code to this:

+ Code Snippet

if upkey = 1 and playerPositionY => 0
    dec playerPositionY, playerSpeed
endif

also, i made my sprite change image as it moved left or right, a sort of tilting effect.

+ Code Snippet

if rightkey() = 1and playerPositionX =< screen width() - sprite width(1)
    inc playerPositionX, playerSpeed
    sprite 1, playerPositionX, playerPositionY, 2`2 is the image for the move right sprite
    else
    sprite 1, playerPositionX, playerPositionY, 1
endif

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Sixty Squares

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Posted: 1st Mar 2007 23:00

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Oh! that's why your post wasn't there before!

Quote: "its funny that no-ones codes the same thing, the same way dontcha think?"

Everybody's different I guess

Anyway, good luck on your project

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