aUCBLogo Demos and Tests / blochequations

be blochequations
   M=FloatArray {0 1 0}
   dM_dt=FloatArray 3
   B=FloatArray {0 1 0}
   B0=1
   B1=0
   Mo=[]
   gamma=1
   M0=1
   T1=100
   T2=100
   t=0
   dt=0.01
   omega=60

   setUpdateGraph false
   perspective
   enableCylinderLines
   black=RGB 0 0 0
   size=350
   forever
   [   clearScreen
      axes
      repeat 5
      [   B.1=B1*sin -omega*t
         B.2=B0
         B.3=B1*cos -omega*t
         dM_dt.1=(gamma*(cross M B).1-    M.1 /T2)
         dM_dt.2=(gamma*(cross M B).2+(M0-M.2)/T1)
         dM_dt.3=(gamma*(cross M B).3-    M.3 /T2)
         M=M+dM_dt*dt
         t=t+dt
      ]
      Mo=fPut M*size Mo
      Home
      setPosXYZ M*size
      setPixel Mo black
      PenUp
      setXYZ 300 0 0
      setHeading 90
      PenDown
      Label List omega Norm M
      updateGraph
      if Key?
      [   ch=readChar
         if ch==Char 27 [break]
         if ch=="0 [B1=0]
         if ch=="1 [B1=0.1]
         if ch=="m [omega=omega*1.01]
         if ch=="l [omega=omega/1.01]
      ]
   ]
end