Difference between revisions of "GlHint"

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(Created page with ''''_glHint:''' specify implementation-specific hints {{PageSyntax}} SUB _glHint (BYVAL target AS _UNSIGNED LONG, BYVAL mode AS _UNSIGNED LONG) void '''_glHint'''(GLenum {{…')
 
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Latest revision as of 10:19, 8 January 2013

_glHint: specify implementation-specific hints


Syntax

 SUB _glHint (BYVAL target AS _UNSIGNED LONG, BYVAL mode AS _UNSIGNED LONG)
 void _glHint(GLenum target, GLenum mode);


target
Specifies a symbolic constant indicating the behavior to be controlled. _GL_LINE_SMOOTH_HINT, _GL_POLYGON_SMOOTH_HINT, _GL_TEXTURE_COMPRESSION_HINT, and _GL_FRAGMENT_SHADER_DERIVATIVE_HINT are accepted.
mode
Specifies a symbolic constant indicating the desired behavior. _GL_FASTEST, _GL_NICEST, and _GL_DONT_CARE are accepted.


Description

Certain aspects of GL behavior, when there is room for interpretation, can be controlled with hints. A hint is specified with two arguments. target is a symbolic constant indicating the behavior to be controlled, and mode is another symbolic constant indicating the desired behavior. The initial value for each target is _GL_DONT_CARE. mode can be one of the following:

_GL_FASTEST

The most efficient option should be chosen.

_GL_NICEST

The most correct, or highest quality, option should be chosen.

_GL_DONT_CARE

No preference. Though the implementation aspects that can be hinted are well defined, the interpretation of the hints depends on the implementation. The hint aspects that can be specified with target, along with suggested semantics, are as follows:

_GL_FRAGMENT_SHADER_DERIVATIVE_HINT

Indicates the accuracy of the derivative calculation for the GL shading language fragment processing built-in functions: _dFdx, _dFdy, and _fwidth.

_GL_LINE_SMOOTH_HINT

Indicates the sampling quality of antialiased lines. If a larger filter function is applied, hinting _GL_NICEST can result in more pixel fragments being generated during rasterization.

_GL_POLYGON_SMOOTH_HINT

Indicates the sampling quality of antialiased polygons. Hinting _GL_NICEST can result in more pixel fragments being generated during rasterization, if a larger filter function is applied.

_GL_TEXTURE_COMPRESSION_HINT

Indicates the quality and performance of the compressing texture images. Hinting _GL_FASTEST indicates that texture images should be compressed as quickly as possible, while _GL_NICEST indicates that texture images should be compressed with as little image quality loss as possible. _GL_NICEST should be selected if the texture is to be retrieved by _glGetCompressedTexImage for reuse.

Notes:

The interpretation of hints depends on the implementation. Some implementations ignore _glHint settings.


Errors

_GL_INVALID_ENUM is generated if either target or mode is not an accepted value.


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/.



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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/.