GLAPI/glHint

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glHint
Core in version 4.4
Core since version 1.0

glHint: specify implementation-specific hints

Function Definition

 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

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/.