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/ IRIX Base Documentation 2001 May / SGI IRIX Base Documentation 2001 May.iso / usr / share / catman / g_man / cat3 / OpenGL / glfeedbackbuffer.z / glfeedbackbuffer
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Text File  |  2001-04-17  |  16.3 KB  |  265 lines
  1.  
  2.  
  3.  
  4. ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr((((3333GGGG))))           OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee           ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr((((3333GGGG))))
  5.  
  6.  
  7.  
  8. NNNNAAAAMMMMEEEE
  9.      ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr - controls feedback mode
  10.  
  11.  
  12. CCCC SSSSPPPPEEEECCCCIIIIFFFFIIIICCCCAAAATTTTIIIIOOOONNNN
  13.      void ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr( GLsizei _s_i_z_e,
  14.                             GLenum _t_y_p_e,
  15.                             GLfloat *_b_u_f_f_e_r )
  16.  
  17.  
  18. PPPPAAAARRRRAAAAMMMMEEEETTTTEEEERRRRSSSS
  19.      _s_i_z_e    Specifies the maximum number of values that can be written into
  20.              _b_u_f_f_e_r.
  21.  
  22.      _t_y_p_e    Specifies a symbolic constant that describes the information that
  23.              will be returned for each vertex.  GGGGLLLL____2222DDDD, GGGGLLLL____3333DDDD, GGGGLLLL____3333DDDD____CCCCOOOOLLLLOOOORRRR,
  24.              GGGGLLLL____3333DDDD____CCCCOOOOLLLLOOOORRRR____TTTTEEEEXXXXTTTTUUUURRRREEEE, and GGGGLLLL____4444DDDD____CCCCOOOOLLLLOOOORRRR____TTTTEEEEXXXXTTTTUUUURRRREEEE are accepted.
  25.  
  26.      _b_u_f_f_e_r  Returns the feedback data.
  27.  
  28. DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
  29.      The ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr function controls feedback.  Feedback, like
  30.      selection, is a GL mode.  The mode is selected by calling ggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee
  31.      with GGGGLLLL____FFFFEEEEEEEEDDDDBBBBAAAACCCCKKKK.  When the GL is in feedback mode, no pixels are
  32.      produced by rasterization.  Instead, information about primitives that
  33.      would have been rasterized is fed back to the application using the GL.
  34.  
  35.      ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr has three arguments:  _b_u_f_f_e_r is a pointer to an array of
  36.      floating-point values into which feedback information is placed.  _s_i_z_e
  37.      indicates the size of the array.  _t_y_p_e is a symbolic constant describing
  38.      the information that is fed back for each vertex.  ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr must
  39.      be issued before feedback mode is enabled (by calling ggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee with
  40.      argument GGGGLLLL____FFFFEEEEEEEEDDDDBBBBAAAACCCCKKKK).  Setting GGGGLLLL____FFFFEEEEEEEEDDDDBBBBAAAACCCCKKKK without establishing the
  41.      feedback buffer, or calling ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr while the GL is in feedback
  42.      mode, is an error.
  43.  
  44.      When ggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee is called while in feedback mode, it returns the number
  45.      of entries placed in the feedback array, and resets the feedback array
  46.      pointer to the base of the feedback buffer. The returned value never
  47.      exceeds _s_i_z_e. If the feedback data required more room than was available
  48.      in _b_u_f_f_e_r, ggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee returns a negative value.  To take the GL out of
  49.      feedback mode, call ggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee with a parameter value other than
  50.      GGGGLLLL____FFFFEEEEEEEEDDDDBBBBAAAACCCCKKKK.
  51.  
  52.      While in feedback mode, each primitive, bitmap, or pixel rectangle that
  53.      would be rasterized generates a block of values that are copied into the
  54.      feedback array.  If doing so would cause the number of entries to exceed
  55.      the maximum, the block is partially written so as to fill the array (if
  56.      there is any room left at all), and an overflow flag is set.  Each block
  57.      begins with a code indicating the primitive type, followed by values that
  58.      describe the primitive's vertices and associated data.  Entries are also
  59.      written for bitmaps and pixel rectangles.  Feedback occurs after polygon
  60.  
  61.  
  62.  
  63.                                                                         PPPPaaaaggggeeee 1111
  64.  
  65.  
  66.  
  67.  
  68.  
  69.  
  70. ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr((((3333GGGG))))           OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee           ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr((((3333GGGG))))
  71.  
  72.  
  73.  
  74.      culling and ggggllllPPPPoooollllyyyyggggoooonnnnMMMMooooddddeeee interpretation of polygons has taken place, so
  75.      polygons that are culled are not returned in the feedback buffer.  It can
  76.      also occur after polygons with more than three edges are broken up into
  77.      triangles, if the GL implementation renders polygons by performing this
  78.      decomposition.
  79.  
  80.      The ggggllllPPPPaaaassssssssTTTThhhhrrrroooouuuugggghhhh command can be used to insert a marker into the
  81.      feedback buffer.  See ggggllllPPPPaaaassssssssTTTThhhhrrrroooouuuugggghhhh.
  82.  
  83.      Following is the grammar for the blocks of values written into the
  84.      feedback buffer.  Each primitive is indicated with a unique identifying
  85.      value followed by some number of vertices.  Polygon entries include an
  86.      integer value indicating how many vertices follow.  A vertex is fed back
  87.      as some number of floating-point values, as determined by _t_y_p_e.  Colors
  88.      are fed back as four values in RGBA mode and one value in color index
  89.      mode.
  90.  
  91.           feedbackList <- feedbackItem feedbackList | feedbackItem
  92.  
  93.           feedbackItem <- point | lineSegment | polygon | bitmap |
  94.           pixelRectangle | passThru
  95.  
  96.           point <- GGGGLLLL____PPPPOOOOIIIINNNNTTTT____TTTTOOOOKKKKEEEENNNN vertex
  97.  
  98.           lineSegment <- GGGGLLLL____LLLLIIIINNNNEEEE____TTTTOOOOKKKKEEEENNNN vertex vertex | GGGGLLLL____LLLLIIIINNNNEEEE____RRRREEEESSSSEEEETTTT____TTTTOOOOKKKKEEEENNNN
  99.           vertex vertex
  100.  
  101.           polygon <- GGGGLLLL____PPPPOOOOLLLLYYYYGGGGOOOONNNN____TTTTOOOOKKKKEEEENNNN n polySpec
  102.  
  103.           polySpec <- polySpec vertex | vertex vertex vertex
  104.  
  105.           bitmap <- GGGGLLLL____BBBBIIIITTTTMMMMAAAAPPPP____TTTTOOOOKKKKEEEENNNN vertex
  106.  
  107.           pixelRectangle <- GGGGLLLL____DDDDRRRRAAAAWWWW____PPPPIIIIXXXXEEEELLLL____TTTTOOOOKKKKEEEENNNN vertex | GGGGLLLL____CCCCOOOOPPPPYYYY____PPPPIIIIXXXXEEEELLLL____TTTTOOOOKKKKEEEENNNN
  108.           vertex
  109.  
  110.           passThru <- GGGGLLLL____PPPPAAAASSSSSSSS____TTTTHHHHRRRROOOOUUUUGGGGHHHH____TTTTOOOOKKKKEEEENNNN value
  111.  
  112.           vertex <- 2d | 3d | 3dColor | 3dColorTexture | 4dColorTexture
  113.  
  114.           2d <- value value
  115.  
  116.           3d <- value value value
  117.  
  118.           3dColor  <- value value value color
  119.  
  120.           3dColorTexture <- value value value color tex
  121.  
  122.           4dColorTexture <- value value value value color tex
  123.  
  124.           color <- rgba | index
  125.  
  126.  
  127.  
  128.  
  129.                                                                         PPPPaaaaggggeeee 2222
  130.  
  131.  
  132.  
  133.  
  134.  
  135.  
  136. ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr((((3333GGGG))))           OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee           ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr((((3333GGGG))))
  137.  
  138.  
  139.  
  140.           rgba <- value value value value
  141.  
  142.           index <- value
  143.  
  144.           tex <- value value value value
  145.  
  146.  
  147.      _v_a_l_u_e is a floating-point number, and _n is a floating-point integer
  148.      giving the number of vertices in the polygon.  GGGGLLLL____PPPPOOOOIIIINNNNTTTT____TTTTOOOOKKKKEEEENNNN,
  149.      GGGGLLLL____LLLLIIIINNNNEEEE____TTTTOOOOKKKKEEEENNNN, GGGGLLLL____LLLLIIIINNNNEEEE____RRRREEEESSSSEEEETTTT____TTTTOOOOKKKKEEEENNNN, GGGGLLLL____PPPPOOOOLLLLYYYYGGGGOOOONNNN____TTTTOOOOKKKKEEEENNNN, GGGGLLLL____BBBBIIIITTTTMMMMAAAAPPPP____TTTTOOOOKKKKEEEENNNN,
  150.      GGGGLLLL____DDDDRRRRAAAAWWWW____PPPPIIIIXXXXEEEELLLL____TTTTOOOOKKKKEEEENNNN, GGGGLLLL____CCCCOOOOPPPPYYYY____PPPPIIIIXXXXEEEELLLL____TTTTOOOOKKKKEEEENNNN and GGGGLLLL____PPPPAAAASSSSSSSS____TTTTHHHHRRRROOOOUUUUGGGGHHHH____TTTTOOOOKKKKEEEENNNN are
  151.      symbolic floating-point constants.  GGGGLLLL____LLLLIIIINNNNEEEE____RRRREEEESSSSEEEETTTT____TTTTOOOOKKKKEEEENNNN is returned
  152.      whenever the line stipple pattern is reset.  The data returned as a
  153.      vertex depends on the feedback _t_y_p_e.
  154.  
  155.      The following table gives the correspondence between _t_y_p_e and the number
  156.      of values per vertex.  _k is 1 in color index mode and 4 in RGBA mode.
  157.  
  158.    ____________________________________________________________________________
  159.    TTTTyyyyppppeeee                  CCCCoooooooorrrrddddiiiinnnnaaaatttteeeessss   CCCCoooolllloooorrrr   TTTTeeeexxxxttttuuuurrrreeee   TTTToooottttaaaallll NNNNuuuummmmbbbbeeeerrrr ooooffff VVVVaaaalllluuuueeeessss
  160.    ____________________________________________________________________________
  161.    GGGGLLLL____2222DDDD                 _x, _y                                      2
  162.    GGGGLLLL____3333DDDD                 _x, _y, _z                                   3
  163.    GGGGLLLL____3333DDDD____CCCCOOOOLLLLOOOORRRR           _x, _y, _z         k                       3 + k
  164.    GGGGLLLL____3333DDDD____CCCCOOOOLLLLOOOORRRR____TTTTEEEEXXXXTTTTUUUURRRREEEE   _x, _y, _z,        k        4              7 + k
  165.    GGGGLLLL____4444DDDD____CCCCOOOOLLLLOOOORRRR____TTTTEEEEXXXXTTTTUUUURRRREEEE   _x, _y, _z, _w      k        4              8 + k
  166.    ____________________________________________________________________________
  167.  
  168.  
  169.      Feedback vertex coordinates are in window coordinates, except _w, which is
  170.      in clip coordinates.  Feedback colors are lighted, if lighting is
  171.      enabled.  Feedback texture coordinates are generated, if texture
  172.      coordinate generation is enabled.  They are always transformed by the
  173.      texture matrix.
  174.  
  175. NNNNOOOOTTTTEEEESSSS
  176.      ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr, when used in a display list, is not compiled into the
  177.      display list but is executed immediately.
  178.  
  179.      When the GGGGLLLL____AAAARRRRBBBB____mmmmuuuullllttttiiiitttteeeexxxxttttuuuurrrreeee extension is supported, ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr
  180.      returns only the texture coordinates of texture unit GGGGLLLL____TTTTEEEEXXXXTTTTUUUURRRREEEE0000____AAAARRRRBBBB.
  181.  
  182. EEEERRRRRRRROOOORRRRSSSS
  183.      GGGGLLLL____IIIINNNNVVVVAAAALLLLIIIIDDDD____EEEENNNNUUUUMMMM is generated if _t_y_p_e is not an accepted value.
  184.  
  185.      GGGGLLLL____IIIINNNNVVVVAAAALLLLIIIIDDDD____VVVVAAAALLLLUUUUEEEE is generated if _s_i_z_e is negative.
  186.  
  187.      GGGGLLLL____IIIINNNNVVVVAAAALLLLIIIIDDDD____OOOOPPPPEEEERRRRAAAATTTTIIIIOOOONNNN is generated if ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr is called while the
  188.      render mode is GGGGLLLL____FFFFEEEEEEEEDDDDBBBBAAAACCCCKKKK, or if ggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee is called with argument
  189.      GGGGLLLL____FFFFEEEEEEEEDDDDBBBBAAAACCCCKKKK before ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr is called at least once.
  190.  
  191.  
  192.  
  193.  
  194.  
  195.                                                                         PPPPaaaaggggeeee 3333
  196.  
  197.  
  198.  
  199.  
  200.  
  201.  
  202. ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr((((3333GGGG))))           OOOOppppeeeennnnGGGGLLLL RRRReeeeffffeeeerrrreeeennnncccceeee           ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr((((3333GGGG))))
  203.  
  204.  
  205.  
  206.      GGGGLLLL____IIIINNNNVVVVAAAALLLLIIIIDDDD____OOOOPPPPEEEERRRRAAAATTTTIIIIOOOONNNN is generated if ggggllllFFFFeeeeeeeeddddbbbbaaaacccckkkkBBBBuuuuffffffffeeeerrrr is executed between
  207.      the execution of ggggllllBBBBeeeeggggiiiinnnn and the corresponding execution of ggggllllEEEEnnnndddd.
  208.  
  209. AAAASSSSSSSSOOOOCCCCIIIIAAAATTTTEEEEDDDD GGGGEEEETTTTSSSS
  210.      ggggllllGGGGeeeetttt with argument GGGGLLLL____RRRREEEENNNNDDDDEEEERRRR____MMMMOOOODDDDEEEE
  211.      ggggllllGGGGeeeetttt with argument GGGGLLLL____FFFFEEEEEEEEDDDDBBBBAAAACCCCKKKK____BBBBUUUUFFFFFFFFEEEERRRR____PPPPOOOOIIIINNNNTTTTEEEERRRR
  212.      ggggllllGGGGeeeetttt with argument GGGGLLLL____FFFFEEEEEEEEDDDDBBBBAAAACCCCKKKK____BBBBUUUUFFFFFFFFEEEERRRR____SSSSIIIIZZZZEEEE
  213.      ggggllllGGGGeeeetttt with argument GGGGLLLL____FFFFEEEEEEEEDDDDBBBBAAAACCCCKKKK____BBBBUUUUFFFFFFFFEEEERRRR____TTTTYYYYPPPPEEEE
  214.  
  215.  
  216. SSSSEEEEEEEE AAAALLLLSSSSOOOO
  217.      ggggllllBBBBeeeeggggiiiinnnn, ggggllllLLLLiiiinnnneeeeSSSSttttiiiipppppppplllleeee, ggggllllPPPPaaaassssssssTTTThhhhrrrroooouuuugggghhhh, ggggllllPPPPoooollllyyyyggggoooonnnnMMMMooooddddeeee, ggggllllRRRReeeennnnddddeeeerrrrMMMMooooddddeeee,
  218.      ggggllllSSSSeeeelllleeeeccccttttBBBBuuuuffffffffeeeerrrr
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  260.  
  261.                                                                         PPPPaaaaggggeeee 4444
  262.  
  263.  
  264.  
  265.