GLPOLYGONSTIPPLE(3G)

NAME
glPolygonStipple - set the polygon stippling pattern

C SPECIFICATION

void glPolygonStipple(const GLubyte * pattern);

PARAMETERS

pattern
    Specifies a pointer to a 32 × 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.

pattern is a pointer to a 32 × 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 format of GL_COLOR_INDEX, and data type of GL_BITMAP. That is, the stipple pattern is represented as a 32 × 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.

If a non-zero named buffer object is bound to the GL_PIXEL_UNPACK_BUFFER target (see glBindBuffer()) while a stipple pattern is specified, pattern is treated as a byte offset into the buffer object's data store.

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 w and y w is sent to the next stage of the GL if and only if the (x w % 32)th bit in the (y w % 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 a non-zero buffer object name is bound to the GL_PIXEL_UNPACK_BUFFER target and the buffer object's data store is currently mapped.

GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to the GL_PIXEL_UNPACK_BUFFER target and the data would be unpacked from the buffer object such that the memory reads required would exceed the data store size.

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

glGet() with argument GL_PIXEL_UNPACK_BUFFER_BINDING

SEE ALSO

glDrawPixels(), glLineStipple(), glPixelStore(), glPixelTransfer()

COPYRIGHT

Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.