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221 lines
8.6 KiB
XML
221 lines
8.6 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
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"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
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<refentry id="glGetShaderPrecisionFormat">
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<refmeta>
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<refentrytitle>glGetShaderPrecisionFormat</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>glGetShaderPrecisionFormat</refname>
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<refpurpose>return the range and precision for different shader numeric formats</refpurpose>
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</refnamediv>
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<refsynopsisdiv><title>C Specification</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glGetShaderPrecisionFormat</function></funcdef>
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<paramdef>GLenum <parameter>shaderType</parameter></paramdef>
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<paramdef>GLenum <parameter>precisionType</parameter></paramdef>
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<paramdef>GLint *<parameter>range</parameter></paramdef>
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<paramdef>GLint *<parameter>precision</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1 id="parameters"><title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><parameter>shaderType</parameter></term>
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<listitem>
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<para>Specifies the type of shader to query.
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Must be either <constant>GL_VERTEX_SHADER</constant>
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or <constant>GL_FRAGMENT_SHADER</constant>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>precisionType</parameter></term>
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<listitem>
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<para>Specifies the numeric format to query, corresponding to a shader precision qualifier and variable type.
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Must be one of <constant>GL_LOW_FLOAT</constant>, <constant>GL_MEDIUM_FLOAT</constant>,
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<constant>GL_HIGH_FLOAT</constant>, <constant>GL_LOW_INT</constant>,
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<constant>GL_MEDIUM_INT</constant>, or <constant>GL_HIGH_INT</constant>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>range</parameter></term>
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<listitem>
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<para>Specifies a pointer to the two-element array in which the
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<inlineequation><mml:math>
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<!-- eqn: log sub 2:-->
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<mml:mrow>
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<mml:msub><mml:mi mathvariant="italic">log</mml:mi>
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<mml:mn>2</mml:mn>
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</mml:msub>
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</mml:mrow>
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</mml:math></inlineequation>
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of the minimum and maximum representable magnitudes of the format
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are returned.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>precision</parameter></term>
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<listitem>
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<para>Specifies a pointer to the location in which the
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<inlineequation><mml:math>
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<!-- eqn: log sub 2:-->
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<mml:mrow>
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<mml:msub><mml:mi mathvariant="italic">log</mml:mi>
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<mml:mn>2</mml:mn>
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</mml:msub>
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</mml:mrow>
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</mml:math></inlineequation>
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of the precision of the format is returned.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id="description"><title>Description</title>
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<para><function>glGetShaderPrecisionFormat</function>
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returns range and precision limits for floating-point and integer shader variable formats with low,
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medium, and high precision qualifiers.
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When <inlineequation><mml:math><mml:mi mathvariant="italic">minRep</mml:mi></mml:math></inlineequation>
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and <inlineequation><mml:math><mml:mi mathvariant="italic">maxRep</mml:mi></mml:math></inlineequation>
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are the minimum and maximum representable values of the format,
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<inlineequation><mml:math>
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<!-- eqn: floor ( log sub 2 ( abs ( minRep ) ) ):-->
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<mml:mrow>
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<mml:mi mathvariant="italic">floor</mml:mi>
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<mml:mo>⁡</mml:mo>
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<mml:mfenced open="(" close=")">
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<mml:mrow>
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<mml:msub><mml:mi mathvariant="italic">log</mml:mi>
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<mml:mn>2</mml:mn>
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</mml:msub>
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<mml:mo>⁡</mml:mo>
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<mml:mfenced open="(" close=")">
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<mml:mrow>
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<mml:mfenced open="|" close="|">
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<mml:mrow>
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<mml:mi mathvariant="italic">minRep</mml:mi>
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</mml:mrow>
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</mml:mfenced>
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</mml:mrow>
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</mml:mfenced>
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</mml:mrow>
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</mml:mfenced>
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</mml:mrow>
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</mml:math></inlineequation>
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and
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<inlineequation><mml:math>
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<!-- eqn: floor ( log sub 2 ( abs ( maxRep ) ) ):-->
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<mml:mrow>
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<mml:mi mathvariant="italic">floor</mml:mi>
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<mml:mo>⁡</mml:mo>
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<mml:mfenced open="(" close=")">
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<mml:mrow>
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<mml:msub><mml:mi mathvariant="italic">log</mml:mi>
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<mml:mn>2</mml:mn>
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</mml:msub>
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<mml:mo>⁡</mml:mo>
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<mml:mfenced open="(" close=")">
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<mml:mrow>
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<mml:mfenced open="|" close="|">
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<mml:mrow>
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<mml:mi mathvariant="italic">maxRep</mml:mi>
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</mml:mrow>
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</mml:mfenced>
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</mml:mrow>
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</mml:mfenced>
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</mml:mrow>
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</mml:mfenced>
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</mml:mrow>
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</mml:math></inlineequation>
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are returned in
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<parameter>range</parameter> as the first and second elements, respectively.</para>
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<para>If the smallest representable value greater than 1 is
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<inlineequation><mml:math>
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<!-- eqn: ( 1 + eps ):-->
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<mml:mfenced open="(" close=")">
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<mml:mrow>
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<mml:mn>1</mml:mn>
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<mml:mo>+</mml:mo>
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<mml:mn>ε</mml:mn>
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</mml:mrow>
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</mml:mfenced>
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</mml:math></inlineequation>
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then
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<inlineequation><mml:math>
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<!-- eqn: floor ( -log sub 2 ( eps ) ):-->
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<mml:mrow>
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<mml:mi mathvariant="italic">floor</mml:mi>
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<mml:mo>⁡</mml:mo>
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<mml:mfenced open="(" close=")">
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<mml:mrow>
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<mml:mo>-</mml:mo>
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<mml:msub><mml:mi mathvariant="italic">log</mml:mi>
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<mml:mn>2</mml:mn>
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</mml:msub>
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<mml:mo>⁡</mml:mo>
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<mml:mfenced open="(" close=")">
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<mml:mrow>
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<mml:mn>ε</mml:mn>
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</mml:mrow>
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</mml:mfenced>
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</mml:mrow>
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</mml:mfenced>
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</mml:mrow>
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</mml:math></inlineequation>
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is returned in <parameter>precision</parameter>.
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An integer format will have an ε of 1, and thus will return 0.
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Floating-point formats will return values greater than 0.</para>
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</refsect1>
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<refsect1 id="notes"><title>Notes</title>
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<para>The minimum range and precision required for different formats is
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described in the <emphasis>OpenGL ES Shading Language Specification.</emphasis></para>
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<para>If a high precision floating-point format is not supported for fragment shaders,
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calling <function>glGetShaderPrecisionFormat</function> with arguments <constant>GL_FRAGMENT_SHADER</constant>
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and <constant>GL_HIGH_FLOAT</constant> will return 0 for both <parameter>range</parameter> and
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<parameter>precision</parameter>. Support for a high precision floating-point format is mandatory for
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vertex shaders.</para>
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<para>Shader compiler support is optional, and thus must be queried
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before use by calling <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry>
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with argument <constant>GL_SHADER_COMPILER</constant>. <citerefentry><refentrytitle>glShaderSource</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glCompileShader</refentrytitle></citerefentry>, <function>glGetShaderPrecisionFormat</function>, and
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<citerefentry><refentrytitle>glReleaseShaderCompiler</refentrytitle></citerefentry> will
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each generate <constant>GL_INVALID_OPERATION</constant> on implementations
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that do not support a shader compiler. Such implementations instead offer the
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<citerefentry><refentrytitle>glShaderBinary</refentrytitle></citerefentry>
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alternative for supplying a pre-compiled shader binary.</para>
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<para>If an error is generated, no change is made to the
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contents of <parameter>range</parameter> or <parameter>precision</parameter>.</para>
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</refsect1>
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<refsect1 id="errors"><title>Errors</title>
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<para><constant>GL_INVALID_OPERATION</constant> is generated if
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a shader compiler is not supported.</para>
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<para><constant>GL_INVALID_ENUM</constant> is generated if
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<parameter>shaderType</parameter> or <parameter>precisionType</parameter> is not
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an accepted value.</para>
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</refsect1>
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<refsect1 id="associatedgets"><title>Associated Gets</title>
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<para><citerefentry><refentrytitle>glGet</refentrytitle></citerefentry>
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with argument <constant>GL_SHADER_COMPILER</constant></para>
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</refsect1>
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<refsect1 id="seealso"><title>See Also</title>
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<para><citerefentry><refentrytitle>glCompileShader</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glShaderSource</refentrytitle></citerefentry></para>
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</refsect1>
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<refsect1 id="copyright"><title>Copyright</title>
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<para>
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Copyright <trademark class="copyright"></trademark> 2008 Khronos Group.
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This material may be distributed subject to the terms and conditions set forth in
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the Open Publication License, v 1.0, 8 June 1999.
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<ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
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</para>
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</refsect1>
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</refentry>
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