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Collision question

Blitz3D Forums/Blitz3D Beginners Area/Collision question

Robert M Jolly(Posted 2006) [#1]
I like to use function in my program as well as types, but i am getting a problem when trying to create collisions.

I put the Collisions command directly before my game loop, and i then in my game loop create objects when a certain action happens. 

While Not Keydown(1) ;
	If MouseHit(1) Then
			Select g_currentweapon
		Case "pistol"
			pistol.weapontype = New weapontype
			;create a new projectile and add it to type_projectile
			pistol\projectile = CreateSphere()
			EntityRadius pistol\projectile, .01
			;make the sphere smaller like a bullet
			ScaleEntity pistol\projectile, .02, .02, .02
			PositionEntity pistol\projectile, EntityX(camera), EntityY(camera), EntityZ(camera)
			TurnEntity pistol\projectile, EntityPitch(camera), EntityYaw(camera), EntityRoll(camera)
			pistol\name$ = "pistol"
			EntityType pistol\projectile, type_projectile
			
	End Select
	End If 

   UpdateWorld()
   RenderWorld()
   Flip



Next


Now collisions will work when that code is inserted direcly in the main game loop like above. But here is the problem. If i get that same exact code and put it into a functin like below, it will never create a collision.

While Not Keydown(1) ;
   ;Here i just replaced the code above with this function
   TestInput()

   UpdateWorld()
   RenderWorld()
   Flip

Next

Function TestInput()

	If MouseHit(1) Then
			Select g_currentweapon
		Case "pistol"
			pistol.weapontype = New weapontype
			;create a new projectile and add it to type_projectile
			pistol\projectile = CreateSphere()
			EntityRadius pistol\projectile, .01
			;make the sphere smaller like a bullet
			ScaleEntity pistol\projectile, .02, .02, .02
			PositionEntity pistol\projectile, EntityX(camera), EntityY(camera), EntityZ(camera)
			TurnEntity pistol\projectile, EntityPitch(camera), EntityYaw(camera), EntityRoll(camera)
			pistol\name$ = "pistol"
			EntityType pistol\projectile, type_projectile
			
	End Select
	End If 
End if 

End Function



Is there a way to get around this problem in blitz3D? I know you can use arrays, but arrays do not offer the same power as types do. When i created a 2d game i had no poblem with testing collisions from space ship that were creating ouside of the main game loop in a function. I know that Blitz3D is different, but is there any command that will allow me still have collisions even if the type is instantiated out side of the main loop?


big10p(Posted 2006) [#2]
Have you remembered to make g_currentweapon global?

[edit] And type_projectile will need global scope, too. I.e. Make sure it's a Const. Just make sure that anything referenced in the function has global scope!


Robert M Jolly(Posted 2006) [#3]
yes i made g_currentweapon global. My types are created properly; the bullets fly across the screen and hit the objects but do not react to the collision unless the types are instantiated in the main game loop. Wierd stuff. :-(


Robert M Jolly(Posted 2006) [#4]
This code workes: Run it for yourself to see

	Graphics3D 1024, 768
	
;Setup Buffer
	SetBuffer BackBuffer()


;Constants: Format (CONSTANT)  ALL CAPS.
	Const ESCKEY% = 1	

;Types:  Format ( xtype ) where x is the name of the type
	Type bullettype
		Field projectile
		Field name$
	End Type

;Object Collision Types: go here format ( type_x = num ) where x = any type name
; and num = any number
	type_bullet = 1
	type_enemy = 2


;Global Variables:  Format ( g_x)  where x = name of variables



;Create the Camera
	camera = CreateCamera()

;Create the Light
	light = CreateLight()
	
	
;Create the cone to shoot at
	cone = CreateCone(10)
	PositionEntity cone, 0,0, 5
	;add the cone to the enemy type
	EntityType cone, type_enemy

;Set up the collisions
	Collisions type_bullet, type_enemy, 2 , 2
;Main Game Loop
	While Not KeyDown(ESCKEY)
	
	If MouseHit(1)
		bullet.bullettype = New bullettype
		bullet\projectile = CreateSphere()
		;makes the bullet originate from the camera
		PositionEntity bullet\projectile, EntityX(camera), EntityY(camera), EntityZ(camera)
		;adds the bullet\projectile to the type_bullet for collision testing
		
		EntityType bullet\projectile, type_bullet
	
	End If 
	
	
	For bullet.bullettype = Each bullettype
		MoveEntity bullet\projectile, 0 , 0 , .1
	Next
	
	For bullet.bullettype = Each bullettype
		;if a collision occured then chage the sphere that hit the cone to red.
		If CountCollisions(bullet\projectile)
			EntityColor bullet\projectile, 255, 0 ,0
		End If 
	
	Next
	
		UpdateWorld ()
		
		RenderWorld() 
		
		Flip
		
	Wend



Now put the code in the main body into a simple function and the colisions will not work.


	Graphics3D 1024, 768
	
;Setup Buffer
	SetBuffer BackBuffer()


;Constants: Format (CONSTANT)  ALL CAPS.
	Const ESCKEY% = 1	

;Types:  Format ( xtype ) where x is the name of the type
	Type bullettype
		Field projectile
		Field name$
	End Type

;Object Collision Types: go here format ( type_x = num ) where x = any type name
; and num = any number
	type_bullet = 1
	type_enemy = 2


;Global Variables:  Format ( g_x)  where x = name of variables



;Create the Camera
	Global camera = CreateCamera()

;Create the Light
	light = CreateLight()
	
	
;Create the cone to shoot at
	cone = CreateCone(10)
	PositionEntity cone, 0,0, 5
	;add the cone to the enemy type
	EntityType cone, type_enemy

;Set up the collisions
	Collisions type_bullet, type_enemy, 2 , 2
;Main Game Loop
While Not KeyDown(ESCKEY)

		TestInput()
	
		UpdateWorld ()
		
		RenderWorld() 
		
		Flip
		
Wend


Function TestInput()
	If MouseHit(1)
		bullet.bullettype = New bullettype
		bullet\projectile = CreateSphere()
		;makes the bullet originate from the camera
		PositionEntity bullet\projectile, EntityX(camera), EntityY(camera), EntityZ(camera)
		;adds the bullet\projectile to the type_bullet for collision testing
		
		EntityType bullet\projectile, type_bullet
	
	End If 
	
	
	For bullet.bullettype = Each bullettype
		MoveEntity bullet\projectile, 0 , 0 , .1
	Next
	
	For bullet.bullettype = Each bullettype
		;if a collision occured then chage the sphere that hit the cone to red.
		If CountCollisions(bullet\projectile)
			EntityColor bullet\projectile, 255, 0 ,0
		End If 
	
	Next

End Function



thanks guys.


big10p(Posted 2006) [#5]
Like I said, make sure everything needed has global scope. Change these to Constants and it works. :)

	Const type_bullet = 1
	Const type_enemy = 2



Robert M Jolly(Posted 2006) [#6]
ok thanks, works great. I put those as global right before i got your message on here and now it works like a charm.

If i use Const does that make it global as well? Thanks!


big10p(Posted 2006) [#7]
Yep. Constants have global scope. You may want to define your constant names using all capitals - I, and I believe most people, use this convention to make constants easily distinguishable from variables.