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/ IRIX Base Documentation 1998 November / IRIX 6.5.2 Base Documentation November 1998.img / usr / share / catman / g_man / cat3 / OpenGL-ftn / fgldepthrange.z / fgldepthrange
Text File  |  1998-10-20  |  4KB  |  133 lines
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  4. ffffggggllllDDDDeeeepppptttthhhhRRRRaaaannnnggggeeee((((3333GGGG))))              OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee              ffffggggllllDDDDeeeepppptttthhhhRRRRaaaannnnggggeeee((((3333GGGG))))
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  8. NNNNAAAAMMMMEEEE
  9.      ffffggggllllDDDDeeeepppptttthhhhRRRRaaaannnnggggeeee - specify mapping of depth values from normalized device
  10.      coordinates to window coordinates
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  13. FFFFOOOORRRRTTTTRRRRAAAANNNN SSSSPPPPEEEECCCCIIIIFFFFIIIICCCCAAAATTTTIIIIOOOONNNN
  14.      SUBROUTINE ffffggggllllDDDDeeeepppptttthhhhRRRRaaaannnnggggeeee( REAL*4 _n_e_a_r,
  15.                                REAL*4 _f_a_r )
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  18. PPPPAAAARRRRAAAAMMMMEEEETTTTEEEERRRRSSSS
  19.      _n_e_a_r  Specifies the mapping of the near clipping plane to window
  20.            coordinates.  The initial value is 0.
  21.  
  22.      _f_a_r   Specifies the mapping of the far clipping plane to window
  23.            coordinates.  The initial value is 1.
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  25. DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
  26.      After clipping and division by _w, depth coordinates range from -1 to 1,
  27.      corresponding to the near and far clipping planes.  ffffggggllllDDDDeeeepppptttthhhhRRRRaaaannnnggggeeee
  28.      specifies a linear mapping of the normalized depth coordinates in this
  29.      range to window depth coordinates.  Regardless of the actual depth buffer
  30.      implementation, window coordinate depth values are treated as though they
  31.      range from 0 through 1 (like color components).  Thus, the values
  32.      accepted by ffffggggllllDDDDeeeepppptttthhhhRRRRaaaannnnggggeeee are both clamped to this range before they are
  33.      accepted.
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  35.      The setting of (0,1) maps the near plane to 0 and the far plane to 1.
  36.      With this mapping, the depth buffer range is fully utilized.
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  38. NNNNOOOOTTTTEEEESSSS
  39.      It is not necessary that _n_e_a_r be less than _f_a_r.  Reverse mappings such as
  40.      near=1, and far=0 are acceptable.
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  42. EEEERRRRRRRROOOORRRRSSSS
  43.      GGGGLLLL____IIIINNNNVVVVAAAALLLLIIIIDDDD____OOOOPPPPEEEERRRRAAAATTTTIIIIOOOONNNN is generated if ffffggggllllDDDDeeeepppptttthhhhRRRRaaaannnnggggeeee is executed between
  44.      the execution of ffffggggllllBBBBeeeeggggiiiinnnn and the corresponding execution of ffffggggllllEEEEnnnndddd.
  45.  
  46. AAAASSSSSSSSOOOOCCCCIIIIAAAATTTTEEEEDDDD GGGGEEEETTTTSSSS
  47.      ffffggggllllGGGGeeeetttt with argument GGGGLLLL____DDDDEEEEPPPPTTTTHHHH____RRRRAAAANNNNGGGGEEEE
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  50. MMMMAAAACCCCHHHHIIIINNNNEEEE DDDDEEEEPPPPEEEENNNNDDDDEEEENNNNCCCCIIIIEEEESSSS
  51.      Although it is possible to reverse the depth mapping so that _n_e_a_r is 1
  52.      and _f_a_r is 0, doing so may cause severe depth-buffering artifacts on
  53.      InfiniteReality systems.  (This is particularly true for 15-bit depth
  54.      buffers.)  Therefore this practice is strongly discouraged.
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  63.                                                                         PPPPaaaaggggeeee 1111
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  70. ffffggggllllDDDDeeeepppptttthhhhRRRRaaaannnnggggeeee((((3333GGGG))))              OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee              ffffggggllllDDDDeeeepppptttthhhhRRRRaaaannnnggggeeee((((3333GGGG))))
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  74. SEE ALSO
  75.      ffffggggllllDDDDeeeepppptttthhhhFFFFuuuunnnncccc, ffffggggllllPPPPoooollllyyyyggggoooonnnnOOOOffffffffsssseeeetttt, ffffggggllllVVVViiiieeeewwwwppppoooorrrrtttt
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  129.                                                                         PPPPaaaaggggeeee 2222
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