glPolygonStipple
- set the polygon stippling pattern
C SPECIFICATION
void glPolygonStipple(
const GLubyte *mask )
delim $$
PARAMETERS
mask
Specifies a pointer to a $32 ~times~ 32$ stipple pattern that will be unpacked
from memory in the same way that glDrawPixels unpacks pixels.
DESCRIPTION
Polygon stippling,
like line stippling
(see glLineStipple),
masks out certain fragments produced by rasterization,
creating a pattern.
Stippling is independent of polygon antialiasing.
mask is a pointer to a $32 ~times~ 32$ stipple pattern that is stored
in memory just like the pixel data supplied to a glDrawPixels
call with
height
and
width
both equal to 32, a pixel
of GL_COLOR_INDEX, and data type
of GL_BITMAP.
That is,
the stipple pattern is represented as a $32 ~times~ 32$ array
of 1-bit color indices packed in unsigned bytes.
glPixelStore parameters like GL_UNPACK_SWAP_BYTES
and GL_UNPACK_LSB_FIRST affect the assembling of the bits into a
stipple pattern.
Pixel transfer operations
(shift, offset, pixel map)
are not applied to the stipple image,
however.
To enable and disable polygon stippling, call
glEnable and glDisable
with argument GL_POLYGON_STIPPLE. Polygon stippling is initially
disabled. If it's enabled,
a rasterized polygon fragment with window coordinates $x sub w$ and $y sub w$
is sent to the next stage of the GL if and only if the
($x sub w~roman mod~32$)th bit in the ($y sub w~roman mod~32$)th row
of the stipple pattern is 1 (one).
When polygon stippling is disabled, it is as if the stipple pattern
consists of all 1's.
ERRORS
GL_INVALID_OPERATION is generated if glPolygonStipple
is executed between the execution of glBegin
and the corresponding execution of glEnd.
ASSOCIATED GETS
glGetPolygonStipple glIsEnabled with argument GL_POLYGON_STIPPLE
