glHint Subroutine

OpenGL 1.2 for AIX: Reference Manual

glHint Subroutine

Purpose

Specifies implementation-specific hints.

Library

OpenGL C bindings library: libGL.a

C Syntax

void glHint( GLenum Target,
   GLenum Mode)

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. Mode can be one of the following three:

GL_FASTEST	The most efficient option should be chosen.
GL_NICEST	The most correct or highest quality option should be chosen.
GL_DONT_CARE	The client does not have a preference. This is the initial setting for all hints.

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:

GL_FOG_HINT	Indicates the accuracy of fog calculation. If per-pixel fog calculation is not efficiently supported by the GL implementation, hinting GL_DONT_CARE or GL_FASTEST can result in per-vertex calculation of fog effects.
GL_LINE_SMOOTH_HINT	Indicates the sampling quality of antialiased lines. Hinting GL_NICEST can result in more pixel fragments being generated during rasterization, if a larger filter function is applied.
GL_PERSPECTIVE_CORRECTION_HINT	Indicates the quality of color and texture coordinate interpolation. If perspective-corrected parameter interpolation is not efficiently supported by the GL implementation, hinting GL_DONT_CARE or GL_FASTEST can result in simple linear interpolation of colors and texture coordinates.
GL_POINT_SMOOTH_HINT	Indicates the sampling quality of antialiased points. Hinting GL_NICEST can result in more pixel fragments being generated during rasterization, if a larger filter function is applied.
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_SUBPIXEL_HINT_IBM	Indicates if primitives are rendered using subpixel sampling techniques. Hinting GL_NICEST can result in a greater accuracy of pixels turned on when a primitive is rendered. GL_FASTEST and GL_DONT_CARE may result in faster, non-subpixel positioned, rendering of some primitives.
GL_CLIP_VOLUME_CLIPPING_HINT_EXT	Indicates whether clip volume clipping is desirable. Hinting GL_NICEST can result in all clipping calculations being performed, while GL_FASTEST can suppress such clipping. GL_FASTEST should only be used when the user is confident that no attempts to render will occur outside the clip volume, for the behavior of the GL library is undefined if any primitive extends beyond the clip volume. This hint is supported if and only if the GL_EXT_clip_volume_hint extension is supported.

Parameters

Target	Specifies a symbolic constant indicating the behavior to be controlled. GL_FOG_HINT, GL_LINE_SMOOTH_HINT, GL_PERSPECTIVE_CORRECTION_HINT, GL_POINT_SMOOTH_HINT, and GL_POLYGON_SMOOTH_HINT are accepted.
Mode	Specifies a symbolic constant indicating the desired behavior. GL_FASTEST, GL_NICEST, and GL_DONT_CARE are accepted.

Notes

The interpretation of hints depends on the implementation. The glHint subroutine can be ignored.

Errors

GL_INVALID_ENUM	Either Target or Mode is not an accepted value.
GL_INVALID_OPERATION	The glHint subroutine is called between a call to glBegin and the corresponding call to glEnd.

Files

/usr/include/GL/gl.h

Contains C language constants, variable type definitions, and ANSI function prototypes for OpenGL.

Related Information

The glBegin or glEnd subroutine.

OpenGL Overview.