I've been having problems implementing sticks. Run the code to see what I mean. It just flies off the screen!
;Verlet Integration
Const bounce#=0.7
Const gravity#=0.8
Const friction#= Float(1.003)
Const fps=12
width=1280
height=800
Graphics width,height,32,0
Type point
Field x
Field y
Field oldx
Field oldy
End Type
Type stick
Field pa
Field pb
Field length
End Type
world.point=New point
world\x=0
world\y=0
world\oldx=world\x-20
world\oldy=world\y-2
world.point=New point
world\x=0
world\y=0
world\oldx=world\x-22
world\oldy=world\y-5
stk.stick=New stick
stk\pa=0
stk\pb=1
length=Distance(stk\pa,stk\pb)
frames=CreateTimer(fps)
While Not KeyHit(1)
Cls
Gosub updatePoints
Gosub updateSticks
Gosub renderPoints
WaitTimer frames
Flip
Wend
;UPDATE POINTS
.updatePoints
For world.point= Each point
vx#= Float((world\x - world\oldx)/friction#)
vy#= Float((world\y - world\oldy)/friction#)
world\oldx = world\x
world\oldy = world\y
world\x = world\x+vx#
world\y = world\y+vy# + gravity
If world\x > width
world\x = width
world\oldx=world\x+vx#*bounce#
EndIf
If world\x < 0
world\x = 0
world\oldx=world\x+vx#*bounce#
EndIf
If world\y > height
world\y = height
world\oldy=world\y+vy#*bounce#
EndIf
If world\y < 0
world\y = 0
world\oldy=world\y+vy#*bounce#
EndIf
Next
Return
;UPDATE STICKS
.updateSticks
For stk.stick= Each stick
dx= GetPointX(stk\pa) - GetPointX(stk\pb)
dy= GetPointY(stk\pa) - GetPointY(stk\pb)
dist = Sqr(dx^2 + dy^2)
If dist = 0 Then dist = 1
diff = stk\length - dist
per = diff / dist / 2
offX = dx * per
offY = dy * per
SetPointX(stk\pa,GetPointX(stk\pa) - offX)
SetPointY(stk\pa,GetPointY(stk\pa) - offY)
SetPointX(stk\pb,GetPointX(stk\pb) + offX)
SetPointY(stk\pb,GetPointY(stk\pb) + offY)
Next
Return
.renderPoints
For world.point= Each point
Oval world\x-5,world\y-5,10,10,1
;Text 0,0,vx
;Text 0,20,vy
Next
Return
Function Distance(pa,pb)
pax=GetPointX(pa)
pay=GetPointY(pa)
pbx=GetPointX(pb)
pby=GetPointY(pb)
ret=Sqr(pa^2 * pb^2)
Return ret
End Function
Function GetPointX(pn)
world.point=First point
For a=1 To pn
world.point=After world
Next
Return world\x
End Function
Function GetPointY(pn)
world.point=First point
For a=1 To pn
world.point=After world
Next
Return world\x
End Function
Function SetPointX(pn,r)
world.point=First point
For a=1 To pn
world.point=After world
Next
world\x=r
End Function
Function SetPointY(pn,r)
world.point=First point
For a=1 To pn
world.point=After world
Next
world\y=r
End Function
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