NewsForumsCodeLogsGallerySpecsSearch

Elastic turning!

Blitz3D Forums/Blitz3D Programming/Elastic turning!

gingerprince(Posted 2006) [#1]
I have a 2D `ship` similar to that in the game Asteroids.
I can move the ship at any given `angle` at a variable `velocity`by using the formula:-

deltax# = velocity *cos(angle)
deltay# = velocity *sin(angle)

The velocity is calculated with acceleration and friction so is not a constant velocity.

As in Asteroids I want to turn the ship so there is an `elastic` turning effect ( like a handbrake turn)

Any suggestions please?

Many thanks.


kevin8084(Posted 2006) [#2]
***EDIT*****
Sorry, just noticed that you specified 2d...
Ignore the post.

Have you tried AlignToVector with the rate# parameter set to >=0 and <1 ?


stayne(Posted 2006) [#3]
The elastic effect only happened if you were holding down the thrust on the original asteroids, correct? Otherwise it just spun?


Stevie G(Posted 2006) [#4]
Non working code but something like this? Note that the maximum speed is implied .. = Acceleration / ( 1.0 - Drag ), which is 5.0 with my settings. You may want to play about with this.

;initialise
Global Acceleration# = .05
Global Drag# = .99
Global TurnSpeed# = .25
Global VelocityX# = 0
Global VelocityY# = 0
Global PositionX# = 0
Global PositionY# = 0
Global Angle# = 0

;define keys
Const KEYleft = 203
Const KEYright = 205
Const KEYthrust = 200


;main loop
While Not KeyDown(1)

	;turning
	Angle = Angle + ( KeyDown( KEYleft ) - KeyDown( KEYright ) ) * TurnSpeed
	;moving
	Thrust# = KeyDown( KEYthrust ) * Acceleration
	VelocityX = VelocityX * Drag + Thrust * Cos( Angle )
	VelocityY = VelocityY * Drag + Thrust * Sin( Angle )
	PositionX = PositionX + VelocityX
	PositionY = PositionY + VelocityY
	;
	;DRAW SHIP @ pos x,y

Wend



jfk EO-11110(Posted 2006) [#5]
In my view you need to seperate acceleration and inertia. So you'll have two bodies in a hierarchy. In 3D this would be easy, parent the ship to a pivot. the ship has the user controls, and the pivot is moved in space. then transfer the acceleration of the ship to the pivot in a delayed way, as well as the rotation (AlignToVector, as suggested). Now you can control the amount of inertia by the speed of the forces equalization.