- specify the line stipple pattern



C SPECIFICATION


PARAMETERS

       _param1  Specifies  a  multiplier for each bit in the line
                stipple pattern.  If _param1 is 3,  for  example,
                each  bit  in  the  pattern  is  used three times
                before the next  bit  in  the  pattern  is  used.
                _param1  is  clamped  to  the  range [1, 256] and
                defaults to 1.

       _param2  Specifies a  16-bit  integer  whose  bit  pattern
                determines  which  fragments  of  a  line will be
                drawn when the line is rasterized.  Bit  zero  is
                used first; the default pattern is all 1's.


DESCRIPTION

       Line  stippling  masks  out  certain fragments produced by
       rasterization; those fragments will  not  be  drawn.   The
       masking  is achieved by using three parameters: the 16-bit
       line stipple pattern _param2, the  repeat  count  _param1,
       and an integer stipple counter s.

       Counter  s  is  reset to 0 whenever glBegin is called, and
       before each  line  segment  of  a  glBegin(GL_LINES)/glEnd
       sequence is generated.  It is incremented after each frag-
       ment of a unit width aliased line segment is generated, or
       after each i fragments of an i width line segment are gen-
       erated.  The i  fragments  associated  with  count  s  are
       masked out if

                    _param2 bit (s/_eqnparam1)mod16

       is  0,  otherwise  these  fragments  are sent to the frame
       buffer.  Bit zero of _param2 is the least significant bit.

       Antialiased  lines  are  treated  as a sequence of 1xwidth
       rectangles for purposes of stippling.  Whether rectagle  s
       is   rasterized  or  not  depends  on  the  fragment  rule
       described for aliased lines,  counting  rectangles  rather
       than groups of fragments.

       To  enable  and  disable line stippling, call glEnable and
       glDisable with argument  GL_LINE_STIPPLE.   When  enabled,
       the  line  stipple  pattern is applied as described above.
       When disabled, it is as if the pattern were all 1's.  Ini-
       tially, line stippling is disabled.


ERRORS

       GL_INVALID_OPERATION is generated if glLineStipple is exe-
       cuted between the execution of glBegin and the correspond-