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56 lines
3.1 KiB
Text
56 lines
3.1 KiB
Text
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'''_glHint:''' specify implementation-specific hints
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{{PageSyntax}}
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SUB _glHint (BYVAL target AS _UNSIGNED LONG, BYVAL mode AS _UNSIGNED LONG)
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void '''_glHint'''(GLenum {{Parameter|target}}, GLenum {{Parameter|mode}});
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; target
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: Specifies a symbolic constant indicating the behavior to be controlled. {{KW|_GL_LINE_SMOOTH_HINT}}, {{KW|_GL_POLYGON_SMOOTH_HINT}}, {{KW|_GL_TEXTURE_COMPRESSION_HINT}}, and {{KW|_GL_FRAGMENT_SHADER_DERIVATIVE_HINT}} are accepted.
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; mode
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: Specifies a symbolic constant indicating the desired behavior. {{KW|_GL_FASTEST}}, {{KW|_GL_NICEST}}, and {{KW|_GL_DONT_CARE}} are accepted.
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{{PageDescription}}
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Certain aspects of GL behavior, when there is room for interpretation, can be controlled with hints. A hint is specified with two arguments. {{Parameter|target}} is a symbolic constant indicating the behavior to be controlled, and {{Parameter|mode}} is another symbolic constant indicating the desired behavior. The initial value for each {{Parameter|target}} is {{KW|_GL_DONT_CARE}}. {{Parameter|mode}} can be one of the following:
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; {{KW|_GL_FASTEST}}
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:
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The most efficient option should be chosen.
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; {{KW|_GL_NICEST}}
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:
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The most correct, or highest quality, option should be chosen.
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; {{KW|_GL_DONT_CARE}}
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:
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No preference.
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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 {{Parameter|target}}, along with suggested semantics, are as follows:
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; {{KW|_GL_FRAGMENT_SHADER_DERIVATIVE_HINT}}
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:
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Indicates the accuracy of the derivative calculation for the GL shading language fragment processing built-in functions: {{KW|_dFdx}}, {{KW|_dFdy}}, and {{KW|_fwidth}}.
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; {{KW|_GL_LINE_SMOOTH_HINT}}
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:
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Indicates the sampling quality of antialiased lines. If a larger filter function is applied, hinting {{KW|_GL_NICEST}} can result in more pixel fragments being generated during rasterization.
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; {{KW|_GL_POLYGON_SMOOTH_HINT}}
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:
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Indicates the sampling quality of antialiased polygons. Hinting {{KW|_GL_NICEST}} can result in more pixel fragments being generated during rasterization, if a larger filter function is applied.
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; {{KW|_GL_TEXTURE_COMPRESSION_HINT}}
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:
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Indicates the quality and performance of the compressing texture images. Hinting {{KW|_GL_FASTEST}} indicates that texture images should be compressed as quickly as possible, while {{KW|_GL_NICEST}} indicates that texture images should be compressed with as little image quality loss as possible. {{KW|_GL_NICEST}} should be selected if the texture is to be retrieved by {{KW|_glGetCompressedTexImage}} for reuse.
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{{PageNotes}}
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The interpretation of hints depends on the implementation. Some implementations ignore '''_glHint''' settings.
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{{PageErrors}}
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{{KW|_GL_INVALID_ENUM}} is generated if either {{Parameter|target}} or {{Parameter|mode}} is not an accepted value.
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{{PageCopyright}}
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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/ http://oss.sgi.com/projects/FreeB/].
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