;moves the bullets and detects collision
Function UpdateBullets()
;check every bullet
For bullet.bullet = Each bullet
;check if the bullet is from the player
If bullet\from = 1
;if player is facing right
If player\direction = MRIGHT
;move the bullet right
bullet\x = bullet\x + 20
EndIf
;if player is facing left
If player\direction = MLEFT
;move the bullet left
bullet\x = bullet\x - 20
EndIf
;End "if bullet\from = 1"
EndIf
;check if the bullet is from the enemy
If bullet\from = 2
;move the bullet left
bullet\x = bullet\x - 20
EndIf
;If bullet is from the player then draw the correct image
If bullet\from = 1
DrawImage (bulletimage, bullet\x, bullet\y)
Else
DrawImage (bulletsimage,bullet\x, bullet\y)
EndIf
;if the bullet is from the player
If bullet\from = 1
;CHECK EVERY ENEMY!
For tank.tank = Each tank
;check to see that the player's bullet and the enemy collided
If ImagesCollide(bulletimage, bullet\x, bullet\y, 0, tankimage,tank\x,tank\y,0)
;subtract a hitpoint
tank\hits = tank\hits - 1
;if there are no hitpoints left delete enemy
If tank\hits <= 0
Delete tank
EndIf
;and the bullet
Delete bullet
EndIf
Next
EndIf
;if the bullet is from an enemy
If bullet\from = 2
;and the player and enemy's bullet collide
If Imagescollide(bimage,bullet\x,bullet\y,0,playerimage,player\x,player\y,0)
;subtract a hitpoint
player\hits = player\hits - 1
;if the player's hits = 0 delete the player
If player\hits <= 0
Delete player
;end the program
End
EndIf
EndIf
;delete the bullet if it collided
Delete bullet
EndIf
Next
End Function blitzbasic
Author
hi guys, im new here, and new to game programming too. Anyway, my code for a 2d shooter game Im making is having problems with the collision. Here is the function im having problems with:
I assume you are loading bimage and playerimage. Have you checked they did actually load?
Try printing out the values in bimage and playerimage. If they are 0 then (I believe) the image hasn't been loaded properly.
Try printing out the values in bimage and playerimage. If they are 0 then (I believe) the image hasn't been loaded properly.
Author
ok, I made sure That those images exist.And they do. I really don't know what the problem is. . . . .
You have "bimage" in the line with the error, but elsewhere you have "bulletimage". Is that perhaps the problem?
edit - I also noticed you have "bulletsimage" in another place. That might be a problem waiting to happen, as well.
[Edited by - Dave Hunt on August 25, 2005 9:20:16 AM]
edit - I also noticed you have "bulletsimage" in another place. That might be a problem waiting to happen, as well.
[Edited by - Dave Hunt on August 25, 2005 9:20:16 AM]
Author
well, actually, i just made it bimage so it would fit on 1 line in this site. And im pretty sure there is something wrong with the player. . . .
In my program,the player's bullets are bulletimage. The enemy's bullets are bulletsimage. Im sorry, it is kinda confusing. so replace the top "bimage" with "bulletimage" and the bottom one with "bulletsimage".
In my program,the player's bullets are bulletimage. The enemy's bullets are bulletsimage. Im sorry, it is kinda confusing. so replace the top "bimage" with "bulletimage" and the bottom one with "bulletsimage".
Ok. Understood.
In your outer loop, if the player is killed, you delete the player object, but the loop continues. So, on the next iteration, you would be referencing the deleted object.
Also, in your inner your loop, if the bullet was from the player and hits an enemy, you delete the bullet. Then you continue checking that bullet against the next enemy. When the inner loop is finished, you then check that (potentially) deleted bullet to see if it was from the player.
From what I can see, you have a number of places where you might be referencing deleted objects.
Without seeing the rest of the code, I can't say what else might be wrong with your objects.
As an aside, when posting code, try surrounding the code with "[ source ]" and "[ /source ]" (without the quotes and spaces). That will maintain your formatting and make it easier for us to read.
In your outer loop, if the player is killed, you delete the player object, but the loop continues. So, on the next iteration, you would be referencing the deleted object.
Also, in your inner your loop, if the bullet was from the player and hits an enemy, you delete the bullet. Then you continue checking that bullet against the next enemy. When the inner loop is finished, you then check that (potentially) deleted bullet to see if it was from the player.
From what I can see, you have a number of places where you might be referencing deleted objects.
Without seeing the rest of the code, I can't say what else might be wrong with your objects.
As an aside, when posting code, try surrounding the code with "[ source ]" and "[ /source ]" (without the quotes and spaces). That will maintain your formatting and make it easier for us to read.
Author
yeah, sorry about that, im new here, so I didn't know how to do that. Thanks for your help, im gonna fool around with the code now and try and make it work.
Oh yeah, Here is all the code in case you need need it.
[Edited by - Porsche911 on August 25, 2005 1:36:44 PM]
Oh yeah, Here is all the code in case you need need it.
Graphics 800,600,0,2;load the image Global tankimage = LoadImage("commando.bmp")Global playerimage = LoadAnimImage("alien.bmp" ,40,55,0,8)Global bulletimage = LoadImage("bullet.bmp")Global grassimage = LoadImage("grass.bmp")Global bulletsimage = LoadImage("FBIbullets.bmp");set the buffer, automidhandle and seedingSetBuffer BackBuffer()AutoMidHandle TrueSeedRnd MilliSecs();directions the player is facingConst MLEFT = 1Const MRIGHT = 2Const RKEY = 205Const LKEY = 203Const UKEY = 200Const DKEY = 205Const SPACE = 57;types__________Type player Field x,y Field frame Field direction Field hitsEnd TypeType bullet Field x,y Field from End Type Type tank Field x,y Field hits Field xv,yvEnd Type;\types_______________;create the playerGlobal player.player = New player;player's coordinates, frame, direction, and hitsplayer\x = 300player\y = 300player\frame = 0player\direction = MLEFTplayer\hits = 1;create the enemyGlobal tank.tank = New tank;tank's coordinates, hits, and velocitytank\x = 400tank\y = 300tank\hits = 15tank\xv = Rand(-5,5) tank\yv = Rand(-5,5);_________________________________________________________________________;MainloopWhile Not KeyDown(1);clear the screenCls;backgroundTileBlock Grassimage ;move player leftIf KeyDown(LKEY) player\x = player\x - 5 player\frame = (player\frame + 1 ) Mod (4) + (4 * (player\direction) -4) player\direction = MLEFT EndIf ;move player rightIf KeyDown(RKEY) player\x = player\x + 5 player\frame = (player\frame + 1 ) Mod (4) + (4 * (player\direction) -4) player\direction = MRIGHT EndIf ;jumping (not finished) If KeyHit(UKEY) player\y = player\y - 20 player\y = player\y + 20 EndIf ;shoot the bullet! If KeyDown(SPACE) Createbullet(player\x + 36, player\y + 22, 1) EndIf ;call all the necessary functions UpdateBullets() drawtank() Drawplayer() AI() ;flip it and wait a fraction of a sec Flip Delay 50 Wend ;_________________________________________________________________________;moves the bullets and detects collisionFunction UpdateBullets() ;check every bullet For bullet.bullet = Each bullet ;check if the bullet is from the player If bullet\from = 1 ;if player is facing right If player\direction = MRIGHT ;move the bullet right bullet\x = bullet\x + 20 EndIf ;if player is facing left If player\direction = MLEFT ;move the bullet left bullet\x = bullet\x - 20 EndIf ;End "if bullet\from = 1" EndIf ;check if the bullet is from the enemy If bullet\from = 2 ;move the bullet left bullet\x = bullet\x - 20 EndIf ;If bullet is from the player or enemy then draw the correct image If bullet\from = 1 DrawImage (bulletimage, bullet\x, bullet\y) Else DrawImage (bulletsimage,bullet\x, bullet\y) EndIf ;if the bullet is from the player If bullet\from = 1 ;CHECK EVERY ENEMY! For tank.tank = Each tank ;check to see that the player's bullet and the enemy collided If ImagesCollide(bulletimage, bullet\x, bullet\y, 0, tankimage, tank\x, tank\y,0) ;subtract a hitpoint tank\hits = tank\hits - 1 ;if there are no hitpoints left delete enemy If tank\hits <= 0 Delete tank EndIf ;and the bullet Delete bullet EndIf Next EndIf ;if the bullet is from an enemy If bullet\from = 2 ;and the player and enemy's bullet collideIf ImagesCollide(bulletsimage,bullet\x,bullet\y,0,playerimage,player\x,player\y,0) ;subtract a hitpoint player\hits = player\hits - 1 ;if the player's hits = 0 delete the player If player\hits <= 0 Delete player ;end the program End EndIf EndIf ;delete the bullet if it collided Delete bullet EndIf Next End Function Function drawtank();this just creates the enemy and playerFor tank.tank = Each tank DrawImage tankimage, tank\x,tank\y Locate 0,0 Print "Tank hits: " + tank\hits NextEnd Function Function drawplayer() For player.player = Each player DrawImage playerimage, player\x, player\y, player\frame Next End Function Function AI();the poor enemy AIFor enemy.tank = Each tank If enemy\y = enemy\y Createbullet(Enemy\x + 36, enemy\y + 22, 2) EndIf enemy\x = enemy\x + enemy\xvIf enemy\x >=790 enemy\xv = -enemy\xvEndIfIf enemy\x <= 10 enemy\xv = -enemy\xvEndIfNext End Function ;_________________________________________________________________________ ;creates the bulletFunction Createbullet(x,y,from)bullet.bullet = New bullet bullet\x = xbullet\y = ybullet\from = fromEnd Function [Edited by - Porsche911 on August 25, 2005 1:36:44 PM]
Author
UPDATE:
When I put a For. . . . Next loop before the
The program works, but If I try to move, It highlights either
Player\x = player\x - 5 (If I am trying to move left)
or
player\x = player\x + 5 (If I am trying to move right)
Also, the enemies bullets don't move
When I put a For. . . . Next loop before the
If ImagesCollide(bulletsimage,bullet\x,bullet\y,0,playerimage,player\x,player\y,0)The program works, but If I try to move, It highlights either
Player\x = player\x - 5 (If I am trying to move left)
or
player\x = player\x + 5 (If I am trying to move right)
Also, the enemies bullets don't move
The only other thing I see is in the section that handles bullets from the enemy. You have the "delete bullet" statement AFTER the EndIf for the collision test. So, you will basically delete every enemy bullet whether it hits the player or not.
You also still have the case where, after deleting a bullet that hits a tank, you then check to see if that bullet came from the player, which should cause an error.
I'm not sure why it would be stopping in your movement code, unless the player object was being deleted somewhere. I don't see anything that would cause that.
You also still have the case where, after deleting a bullet that hits a tank, you then check to see if that bullet came from the player, which should cause an error.
I'm not sure why it would be stopping in your movement code, unless the player object was being deleted somewhere. I don't see anything that would cause that.
This topic is closed to new replies.
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