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GFA-BASIC Atari  |  1996-09-02  |  1KB  |  43 lines
  1. ' Tunnel projection
  2. '
  3. '
  4. '
  5. RESERVE 600000
  6. ' VOID XBIOS(5,L:-1,L:-1,0)
  7. tunnel%=MALLOC(640*200*2)
  8. mem%=tunnel%
  9. zs%=700
  10. ystart#=-40.4
  11. xstart#=-80
  12. yy%=20
  13. xx%=40
  14. '
  15. FOR y#=ystart# TO ystart#+99                    !200 pixels high
  16.   FOR x#=xstart# TO xstart#+199                 !400 pixels wide
  17.     IF x#-xx%<>0
  18.       x1#=x#-xx%
  19.     ELSE
  20.       x1#=1E-05
  21.     ENDIF
  22.     p%=(ATN((y#-yy%)/(x1#))/2/PI)*32*8                   !.....
  23.     '
  24.     l#=SQR(x1#*x1#+(y#-yy%)*(y#-yy%))/4                  !These two are the problems
  25.     IF l#<>0
  26.       dist%=(zs%/l#)+0.5
  27.       l%=(((p%+dist%/3) AND 31)*2)+(64*2*(dist% AND 31))
  28.       DPOKE mem%,l%
  29.     ELSE
  30.       DPOKE mem%,0
  31.     ENDIF
  32.     ADD mem%,2
  33.   NEXT x#
  34.   PSET y#+100,0,-1
  35. NEXT y#
  36. '
  37. BSAVE "d:\source2\m21.st\data\tunnel.dat",tunnel%,mem%-tunnel%
  38. REPEAT
  39.   k$=INKEY$
  40. UNTIL k$<>""
  41. CLS
  42. PRINT mem%-tunnel%
  43.