General linepick question

Blitz3D Forums/Blitz3D Programming/General linepick question

cash	(Posted 2004) [#1]

I have not had much luck with linepick in my games so have avoided it, however the more I look through the posts I read more and more about people using linepick.

Can anyone give me examples (not code necessarily) of where linepick may be used over and above other similar code.

This may sound strange but I want to get the most from Blitz and sometimes wonder whether certain functions perform better in certain conditions than others.

Jeppe Nielsen

(Posted 2004) [#2]

You could use a linepick if you want to know if there is a "ground" beneath something, or you want to place an entity on top of another, you could use a linepick instead of using collisions. The command has many uses, this is just a few.

jhocking

(Posted 2004) [#3]

Linepick is also very useful for doing instantaneous shots in shooting games. When the player shoots use Linepick to determine what was hit.

Along the lines of what Jeppe described, I use Linepick a lot with enemy characters, to determine if they are facing the player.

Ross C

(Posted 2004) [#4]

Hey man, this is a linepick example.

USE arrow keys to move, and spacebar to jump. Line pick used to see if the cone is still 'jumping'

PositionEntity cube5,-4,11,12
EntityPickMode cube5,2
EntityType cube5,2

Global cube6=CreateCube()
PositionEntity cube6,-6,13,10
EntityPickMode cube6,2
EntityType cube6,2

Global cube7=CreateCube()
PositionEntity cube7,0,13,20
ScaleEntity cube7,4,0.2,4
EntityPickMode cube7,2
EntityType cube7,2

Global sphere=CreateSphere(10)
ScaleEntity sphere,10,1,10
EntityPickMode sphere,2
EntityType sphere,2
PositionEntity sphere,-2,0,19

Collisions 1,2,2,2; set up collisions between the ground and the player

Global jump_force#
Global jump_flag=0; set jump flag to 'no jump'
Global gravity#=0.9; set gravity value

While Not KeyHit(1)

	
	LinePick(EntityX(player,True),EntityY(player,True),EntityZ(player,True),0,-30,0); do a linepick straight down form the players location
	
	If jump_flag=0 Then
		If EntityY#(player,True)-PickedY()>1.05 Then; WARNING. THIS NUMBER MUST BE SLIGHTLY LARGER THAN THE PLAYERS ENTITYRADIUS.
		; ABOVE. if the players y position is greater than a distance of 1.05, then make the player fall.
		; Since the players entity radius is 1, This number must be slightly greater than 1, so that the collision
		; system doesn't work.
			jump_flag=1; set jump flag to jump
			jump_force=0.02; set jump force to 0.02. You cannot set this to 0. It must always be slightly more
		End If
	End If


	If KeyHit(57) And jump_flag=0 Then; if user presses spacebar
		jump_flag=1; set jump flag to 'jump'
		jump_force=0.4; set jumping force. make larger for higher jump
	End If
		
	
	If KeyDown(200) Then MoveEntity player,0,0,0.1
	If KeyDown(208) Then MoveEntity player,0,0,-0.1
	If KeyDown(203) Then TurnEntity player,0,1,0
	If KeyDown(205) Then TurnEntity player,0,-1,0	
	
	If jump_flag=1 Then; if jump flag set then 'jump'
		update_jump()
	End If
	update_camera()
	
	UpdateWorld
	RenderWorld
	Text 0,0," Press Space to jump. Arrow keys to move!"
	;DebugLog(" pickedy="+PickedY())
	Flip
Wend
End

Function update_camera()
	RotateEntity camera,EntityPitch(player),EntityYaw(player),EntityRoll(player); make the camera equal to the rotations of the camera
	PositionEntity camera,EntityX(player),EntityY(player)+2,EntityZ(player); position the camera at the x and z pos of the player
	MoveEntity camera,0,0,-7; move the camera back from the player by 7 units
	PointEntity camera,player
End Function

Function update_jump()

	jump_force=jump_force*gravity; apply gravity to the jumping force

	MoveEntity player,0,jump_force,0; move the player
	If jump_force>0 And jump_force<0.05 Then; when players upward speed reaches alomost zero, reverse it
											; make smaller to keep player in the air for longer
		jump_force=jump_force*-1; reverse the jumping force
		gravity=gravity+(2*(1-gravity)); turn gravity around
	End If
	If jump_force<-0.5 Then jump_force=-0.5; stop the player from falling to quick
	If EntityCollided(player,2) Then; if the player has collided with the ground
		If EntityY(player,True)-PickedY()<=1 Then; WARNING. THIS NUMBER MUST BE THE SAME AS THE PLAYER'S ENTITYRADIUS
			jump_force=0; reset the jumping force
			jump_flag=0; reset jump flag back to zero (not jumping)
			gravity=gravity-(2*(gravity-1)); reset gravity
		End If
	End If
End Function