GLSAMPLECOVERAGE(3G)

NAME
glSampleCoverage - specify multisample coverage parameters

C SPECIFICATION

void glSampleCoverage(GLclampf value, GLboolean invert);

PARAMETERS

value
    Specify a single floating-point sample coverage value. The value is clamped to the range 0 1. The initial value is 1.0.

invert
    Specify a single boolean value representing if the coverage masks should be inverted. GL_TRUE and GL_FALSE are accepted. The initial value is GL_FALSE.

DESCRIPTION

Multisampling samples a pixel multiple times at various implementation-dependent subpixel locations to generate antialiasing effects. Multisampling transparently antialiases points, lines, polygons, bitmaps, and images if it is enabled.

value is used in constructing a temporary mask used in determining which samples will be used in resolving the final fragment color. This mask is bitwise-anded with the coverage mask generated from the multisampling computation. If the invert flag is set, the temporary mask is inverted (all bits flipped) and then the bitwise-and is computed.

If an implementation does not have any multisample buffers available, or multisampling is disabled, rasterization occurs with only a single sample computing a pixel's final RGB color.

Provided an implementation supports multisample buffers, and multisampling is enabled, then a pixel's final color is generated by combining several samples per pixel. Each sample contains color, depth, and stencil information, allowing those operations to be performed on each sample.

NOTES

glSampleCoverage is available only if the GL version is 1.3 or greater.

ERRORS

GL_INVALID_OPERATION is generated if glSampleCoverage is executed between the execution of glBegin() and the corresponding execution of glEnd().

ASSOCIATED GETS

glGet() with argument GL_SAMPLE_COVERAGE_VALUE

glGet() with argument GL_SAMPLE_COVERAGE_INVERT

glIsEnabled() with argument GL_MULTISAMPLE

glIsEnabled() with argument GL_SAMPLE_ALPHA_TO_COVERAGE

glIsEnabled() with argument GL_SAMPLE_ALPHA_TO_ONE

glIsEnabled() with argument GL_SAMPLE_COVERAGE

SEE ALSO

glEnable(), glPushAttrib()

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/.