Whirlpool effect

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Jim Brown

Cool!
There's another one here but I can't remember the author of this code. Possibly FredBorg(?)
Use this image for a nice effect:

; Vortex demo.
; Creates custom cone.  Apex of cone <===> center of texture.
; Oriented so apex is on z+ axis, interior of cone is visible.

Graphics3D 640, 480

tx = LoadTexture("vortex2.jpg") ; image should be square, perhaps 256 x 256.
VortexCone = createVortexCone(24,32) ; try different heights
EntityTexture VortexCone, tx
EntityFX VortexCone, 1 ; full bright

cam = CreateCamera( )
PositionEntity cam, 0,0,-3
CameraZoom cam, 3.8 ; zoom >= 3.8 fills the screen

While Not KeyDown(1)
 TurnEntity VortexCone, 0,0, -.26
 RenderWorld : Flip
Wend
End

Function CreateVortexCone(segments=24,height=1)
 Local n, m,s, a#,t#, u#,v# 
 m=CreateMesh()
 s=CreateSurface(m)
 a=360.0/segments
 ; First two vertices are apex and one point on the base.
 AddVertex s,0,0,height,0.5,0.5     ; vertex 0
 AddVertex s,Cos(t),Sin(t),0,1,0.5  ; vertex 1
 For n=2 To segments
  t=t+a : u=(1+Cos(t))/2 : v=(1-Sin(t))/2
  AddVertex s,Cos(t),Sin(t),0,u,v  ; vertex n
  AddTriangle s,0,n,n-1
 Next 
 AddTriangle s,0,1,n-1
 Return m
End Function