I haven't looked at your code at length but you're probably better using verlet integration for this kind of thing. Weibo of Thrust Extreme fame posted some code a while back which could prove useful. Basically, you assign specific weight to pointmasses which then determines their influence during the constraint phase.
Found it ...
Found it ...
Open in online IDE; quick thrust game, by Wiebo de Wit ; Using verlet integration for movement and stick constraints for the ball and chain =] ; green line is your ship. I'm sorry but i didn't have the strength to include my new ; vector object engine. a and s to rotate, r-shift to thrust Const TIMESTEP# = 0.05 Const GRAVITYANGLE = 0 ; 0 = straight down, 90 = right, etc Const GRAVITYFORCE# = 10 Const DRAG# = 0.995 Const THRUST# = 40 Const NUM_PARTICLES = 5 Const RESTLENGTH# = 20 Type Particle Field x#, y# Field old_x#, old_y# Field a_x#, a_y# Field mass# Field nxt.particle End Type Type Player Field angle# Field thrust# Field point.particle End Type Global player.player, p.particle Graphics 640,480 SetBuffer BackBuffer() ; create player player.player = New player ; player is a particle too, but you can control it player\point = New particle p.particle = player\point p\x = 200 : p\y = 200 p\old_x = 200 : p\old_y = 200 p\a_x = 0 : p\a_y = 0 ; make ship heavy p\mass =1 For count = 1 To NUM_PARTICLES p\nxt = New particle p = p\nxt p\x = 200 : p\y = 200 p\old_x = Rand(200,205) p\old_y = Rand(200,205) p\a_x = 0 : p\a_y = 0 p\mass = 60 Next ; last particle is ball. make heavy p\mass = 1 ; loop While KeyHit( 1 ) = False GetInput() ApplyPhysics() Verlet() ConstrainParticlesMass() DrawParticles() Flip Cls Wend ; ------------------------------------------------------------ Function GetInput() If KeyDown( 203 ) ;rotate player\angle = player\angle + 5 EndIf If KeyDown( 205 ) ;rotate player\angle = player\angle - 5 EndIf If KeyDown( 200 ) ;thrust, adjust player particle acceleration p.particle = player\point p\a_x = p\a_x - Sin( player\angle ) * THRUST p\a_y = p\a_y - Cos( player\angle ) * THRUST EndIf End Function Function ApplyPhysics() ; apply gravity to particles For p.particle = Each particle p\a_x = p\a_x + Sin( GRAVITYANGLE ) * GRAVITYFORCE / p\mass p\a_y = p\a_y + Cos( GRAVITYANGLE ) * GRAVITYFORCE / p\mass Next End Function Function ConstrainParticlesMass() p.particle = player\point While p\nxt <> Null dx# = p\nxt\x - p\x dy# = p\nxt\y - p\y deltalength# = Sqr( dx*dx + dy*dy ) diff# = ( deltalength - RESTLENGTH ) / (deltalength * ( -p\mass + -p\nxt\mass ) ) p\x = p\x + -p\mass * dx * diff p\y = p\y + -p\mass * dy * diff p = p\nxt p\x = p\x - -p\mass * dx * diff p\y = p\y - -p\mass * dy * diff Wend End Function Function DrawParticles() p.particle = player\point ; draw player, green line Color 0,255,0 dx# = Sin( player\angle) dy# = Cos( player\angle) Line p\x-dx*20, p\y-dy*20 , p\x + dy*5, p\y - dx*5 Line p\x-dx*20, p\y-dy*20 , p\x - dy*5, p\y + dx*5 Line p\x + dy*5, p\y - dx*5, p\x - dy*5, p\y + dx*5 ; draw line Color 255,0,0 While p\nxt <> Null Line p\x, p\y, p\nxt\x, p\nxt\y p = p\nxt Wend ; draw ball at end Color 255,255,0 Oval p\x -14, p\y-14, 28,28, 0 ; white dots, for clarity Color 255,255,255 For p.particle =Each particle Plot p\x, p\y Next End Function Function Verlet() ; eg: move particles, introducing drag For p.particle = Each particle x# = p\x y# = p\y tempx# = p\x tempy# = p\y oldx# = p\old_x oldy# = p\old_y p\x = p\x + DRAG * x - DRAG * oldx + p\a_x * TIMESTEP * TIMESTEP p\y = p\y + DRAG * y - DRAG * oldy + p\a_y * TIMESTEP * TIMESTEP p\old_x = tempx p\old_y = tempy ; reset acceleration after moving particle p\a_x = 0 : p\a_y = 0 Next End Function