glPolygonStipple

NAME

glPolygonStipple -- set the polygon stippling pattern

C SPECIFICATION

void glPolygonStipple(const GLubyte *mask)

PARAMETERS

mask: 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.

mask is a pointer to a 32*32 stipple pattern that is stored in memory just like the pixel data supplied to a glDrawPixels 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.

Polygon stippling is enabled and disabled with glEnable and glDisable, using argument GL_POLYGON_STIPPLE. If enabled, a rasterized polygon fragment with window coordinates xw and yw is sent to the next stage of the GL if and only if the (xw mod 32)th bit in the (yw mod 32)th row of the stipple pattern is one. When polygon stippling is disabled, it is as if the stipple pattern were all ones.

ERRORS

GL_INVALID_OPERATION is generated if glPolygonStipple is called between a call to glBegin and the corresponding call to glEnd.

ASSOCIATED GETS

glGetPolygonStipple
glIsEnabled with argument GL_POLYGON_STIPPLE