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Adding acceleration to pathfinding enemies...

BlitzMax Forums/BlitzMax Beginners Area/Adding acceleration to pathfinding enemies...

spraycanmansam(Posted 2009) [#1]
Im making a 2d space shoot-em up where the character stays center-screen but roams the 'world' ..basically everything's position on-screen is offset by where the player is in the 'world'.

I have an enemy that when you get within range will power up and start to hunt you... now I've coded the hunting part, but I want to add acceleration, friction, etc so its not so 'on/off'

I've got the accel/friction idea working great for the player, but I cant seem to get it right for the enemy :/

Here's a snippet of the enemy code...



Local dirX:Float = 1
Local dirY:Float = 0

Local speed:Float = 5
Local turnSpeed:Float = 250

		'is player in range? if so power up.. if not lay dormant
		If( isOn = 1 )

			'hunt
			Local dX:Float = Player.worldX - worldX
			Local dY:Float = Player.worldY - worldY
			Local distanceLength:Float = Sqr( dX * dX + dY * dY )
			
			dX:/ distanceLength
			dY:/ distanceLength
			
			If dY * dirX - dX * dirY > 0 Then
				
				dirX = Cos( Pi / 180.0 * turnSpeed ) * dirX - Sin( Pi / 180.0 * turnSpeed ) * dirY
				dirY = Cos( Pi / 180.0 * turnSpeed ) * dirY + Sin( Pi / 180.0 * turnSpeed ) * dirX
	
				If dY * dirX - dX * dirY < 0 Then
					dirX = dX
					dirY = dY
				EndIf
				
			Else
				
				dirX = Cos( -Pi / 180.0 * turnSpeed ) * dirX - Sin( -Pi / 180.0 * turnSpeed ) * dirY
				dirY = Cos( -Pi / 180.0 * turnSpeed ) * dirY + Sin( -Pi / 180.0 * turnSpeed ) * dirX
		
				If dY * dirX - dX * dirY < 0 Then
					dirX = dX
					dirY = dY
				EndIf
				
			End If
			
			
			worldX:+ ( dirX * speed )
			worldY:+ ( dirY * speed )
							
		Else 
	
					
		End If


Any help would be great :)


Jesse(Posted 2009) [#2]
did you convert this code from c to BlitzMax? The reason I am asking is because Pi/180.0 is used to convert degrees to radian but all of the Trig functions in BlitzMax work in degrees and I believe the standard trig functions in c work with radians. Instead of doing all of that extra math, jut remove the whole pi/180.0 out of all of the equations and change the turnSpeed speed value to a small number like maybe 2.

so it will look something like this:
turnSpeed = 2.0
.
.
				dirX = Cos(turnSpeed ) * dirX - Sin(turnSpeed ) * dirY

don't forget to keep the negative sign on the lower equations.
I don't really know what that formula i supposed to do because I can't figure out how it's working and I don't have a working(runnable) example.

I have some code in the code archive for a chaser missile that should do what you want:
http://www.blitzmax.com/codearcs/codearcs.php?code=2045
it's not perfect but it should work fairly well for a constant frame rate(flip(-1)). yours might work better but unless you provide a runnable example I won't know.