To Next Page

To Previous Page

glPolygonStipple

Chapter 14

344

glPolygonStipple

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

anti-aliasing.

*mask 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.

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

and y

is sent to the next stage

of the GL if and only if the (x

mod 32)th bit in the (y

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 1s.

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

HP b2600 Reference Guide

Other manuals for HP b2600