GlHint
_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:
The most efficient option should be chosen.
The most correct, or highest quality, option should be chosen.
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:
Indicates the accuracy of the derivative calculation for the GL shading language fragment processing built-in functions: _dFdx, _dFdy, and _fwidth.
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.
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.
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/.
