Rem **************************************************************************
Rem *
Rem * Cosplot2 by Dan Rhea - Converted from a Microsoft basic demo I did for
Rem *                        The Atari 8-Bit machine. Basicly is shows some
Rem * 3D graphics, hidden line removal and most important! Speed, this program
Rem * takes nearly 40 min to run on an 80XL.
Rem *
Rem **************************************************************************
Rem *
Rem ** Declare data and alert boxes
Rem *
A$="Cosplot2-ST  by Dan Rhea|========================|Press both mouse buttons|  to stop  the program"
B$="    Select resolution   "
Cx=639
Cy=399
Rh=60
D=1800
Th=0.4
S1=Sin(Th)
C1=Cos(Th)
Ph=1.25
S2=Sin(Ph)
C2=Cos(Ph)
Ar=640
Dim Yn(Ar)
Dim Yx(Ar)
Rem *
Rem ** Open us a full window and get a contrasting color
Rem *
Openw 0,0,0
Fullw 0
Color 1
Defline 1,1,0,0
Rem *
Rem ** Init the display arrays
Rem *
For I=1 To Ar-1
  Yn(I)=Cx
  Yx(I)=Cx
Next I
Rem *
Rem ** Pick the formula and resolution
Rem *
B1=0
Alert 0,A$,1,"Form 1|Form 2|Quit",B1
If B1=3 Then
  End
Endif
Alert 0,B$,1,"High|Med|Nope!",B2
If B2=3 Then
  End
Endif
If B2=1 Then
  St=-1
Else
  St=-0.5
  Cy=199
Endif
Rem *
Rem ** Hide the mouse and start drawing
Rem *
Hidem
For X=8 To -95 Step St
  Fl=0
  For Y=-75 To 4
    If B1=1 Then
      Gosub Cosfu1(0.06)
    Else
      Gosub Cosfu2(0.06)
    Endif
    Z=Num
    Rem *
    Rem ** See if they want to quit
    Rem *
    B=Mousek
    If B=3 Then
      Showm
      Stop
      Hidem
    Endif
    Gosub Findhide(0)
  Next Y
Next X
Rem *
Rem ** Wait here till we are told to quit
Rem
Showm
Here:
B=Mousek
If B=3 Then
  End
Endif
Goto Here
Rem *
Rem ** Handle the sacaling, slope and hidden line removal of the plot
Rem *
Procedure Findhide(Dum1)
  Rem *
  Rem ** Simulate the 3D effect and use Cosine coordinates
  Rem *
  Xe=-X*S1+Y*C1
  Ye=-X*C1*C2-Y*S1*C2+Z*S2
  Ze=-X*S2*C1-Y*S2*S1-Z*C2+Rh
  Sx=D*(Xe/Ze)+Cx
  Sy=-D*(Ye/Ze)+Cy
  If Fl=0 Then
    Fl=1
    F=0
  Else
    Dx=Ox-Sx
    If Dx=0 Then
      Dx=1
    Endif
    Sl=(Oy-Sy)/Dx
    Yp=Oy
    For Xp=Int(Ox)+1 To Sx
      Fg=1
      Yp=Yp+Sl
      Rem *
      Rem ** Most of the following is for hidden line removal
      Rem *
      If Xp<0 Or Xp>Cx Then
        Fg=0
        F=0
        Goto Merge
      Endif
      If Yp<0 Or Yp>Cy Then
        Fg=0
        F=0
      Endif
      Rem *
      Rem ** Go for the appropriate plot routine
      Rem *
      If Yp<=Yn(Xp) Then
        Gosub Makeit1(0)
        If Yp<Yx(Xp) Then
          Goto Merge
        Else
          Gosub Makeit2(0)
        Endif
        If Yp>=Yx(Xp) Then
          Gosub Makeit2(0)
          Goto Merge
        Endif
        F=0
      Endif
      Merge:
    Next Xp
  Endif
  Ox=Sx
  Oy=Sy
Return
Rem *
Rem ** Normal draw routine
Rem *
Procedure Makeit1(Dum2)
  Yn(Xp)=Yp
  If Fg<>0 Then
    If F=0 Then
      Plot Xp,Yp
      F=1
    Endif
    Draw Xp,Yp
  Endif
Return
Rem *
Rem ** Special routine for the edges
Rem *
Procedure Makeit2(Dum3)
  Yx(Xp)=Yp
  If Fg<>0 Then
    If F=0 Then
      Plot Xp,Yp
      F=1
    Endif
    Draw Xp,Yp
  Endif
Return
Rem *
Rem ** Distant Plot formula
Rem *
Procedure Cosfu1(Ival)
  Num=Sqr((Cos(Ival*(X*X+Y*Y)))*(Cos(Ival*(X*X+Y*Y))))
Return
Rem *
Rem ** Closeup plot formula
Rem *
Procedure Cosfu2(Ival)
  Num=Cos(Ival*(X*X+Y*Y))
Return
End