1991-2006
Silicon Graphics, Inc.
glSampleCoverage
3G

# 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/.