| 1 | <?xml version="1.0" encoding="UTF-8"?> |
| 2 | <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN" |
| 3 | "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd"> |
| 4 | <refentry id="glGetUniform"> |
| 5 | <refmeta> |
| 6 | <refentrytitle>glGetUniform</refentrytitle> |
| 7 | <manvolnum>3G</manvolnum> |
| 8 | </refmeta> |
| 9 | <refnamediv> |
| 10 | <refdescriptor>glGetUniform</refdescriptor> |
| 11 | <refname>glGetUniformfv</refname> |
| 12 | <refname>glGetUniformiv</refname> |
| 13 | <refpurpose>Returns the value of a uniform variable</refpurpose> |
| 14 | </refnamediv> |
| 15 | <refsynopsisdiv><title>C Specification</title> |
| 16 | <funcsynopsis> |
| 17 | <funcprototype> |
| 18 | <funcdef>void <function>glGetUniformfv</function></funcdef> |
| 19 | <paramdef>GLuint <parameter>program</parameter></paramdef> |
| 20 | <paramdef>GLint <parameter>location</parameter></paramdef> |
| 21 | <paramdef>GLfloat *<parameter>params</parameter></paramdef> |
| 22 | </funcprototype> |
| 23 | <funcprototype> |
| 24 | <funcdef>void <function>glGetUniformiv</function></funcdef> |
| 25 | <paramdef>GLuint <parameter>program</parameter></paramdef> |
| 26 | <paramdef>GLint <parameter>location</parameter></paramdef> |
| 27 | <paramdef>GLint *<parameter>params</parameter></paramdef> |
| 28 | </funcprototype> |
| 29 | </funcsynopsis> |
| 30 | </refsynopsisdiv> |
| 31 | <refsect1 id="parameters"><title>Parameters</title> |
| 32 | <variablelist> |
| 33 | <varlistentry> |
| 34 | <term><parameter>program</parameter></term> |
| 35 | <listitem> |
| 36 | <para>Specifies the program object to be |
| 37 | queried.</para> |
| 38 | </listitem> |
| 39 | </varlistentry> |
| 40 | <varlistentry> |
| 41 | <term><parameter>location</parameter></term> |
| 42 | <listitem> |
| 43 | <para>Specifies the location of the uniform variable |
| 44 | to be queried.</para> |
| 45 | </listitem> |
| 46 | </varlistentry> |
| 47 | <varlistentry> |
| 48 | <term><parameter>params</parameter></term> |
| 49 | <listitem> |
| 50 | <para>Returns the value of the specified uniform |
| 51 | variable.</para> |
| 52 | </listitem> |
| 53 | </varlistentry> |
| 54 | </variablelist> |
| 55 | </refsect1> |
| 56 | <refsect1 id="description"><title>Description</title> |
| 57 | <para><function>glGetUniform</function> returns in |
| 58 | <parameter>params</parameter> the value(s) of the specified |
| 59 | uniform variable. The type of the uniform variable specified by |
| 60 | <parameter>location</parameter> determines the number of values |
| 61 | returned. If the uniform variable is defined in the shader as a |
| 62 | boolean, int, or float, a single value will be returned. If it |
| 63 | is defined as a vec2, ivec2, or bvec2, two values will be |
| 64 | returned. If it is defined as a vec3, ivec3, or bvec3, three |
| 65 | values will be returned, and so on. To query values stored in |
| 66 | uniform variables declared as arrays, call |
| 67 | <function>glGetUniform</function> for each element of the array. |
| 68 | To query values stored in uniform variables declared as |
| 69 | structures, call <function>glGetUniform</function> for each |
| 70 | field in the structure. The values for uniform variables |
| 71 | declared as a matrix will be returned in column major |
| 72 | order.</para> |
| 73 | |
| 74 | <para>The locations assigned to uniform variables are not known |
| 75 | until the program object is linked. After linking has occurred, |
| 76 | the command |
| 77 | <citerefentry><refentrytitle>glGetUniformLocation</refentrytitle></citerefentry> |
| 78 | can be used to obtain the location of a uniform variable. This |
| 79 | location value can then be passed to |
| 80 | <function>glGetUniform</function> in order to query the current |
| 81 | value of the uniform variable. After a program object has been |
| 82 | linked successfully, the index values for uniform variables |
| 83 | remain fixed until the next link command occurs. The uniform |
| 84 | variable values can only be queried after a link if the link was |
| 85 | successful.</para> |
| 86 | </refsect1> |
| 87 | <refsect1 id="notes"><title>Notes</title> |
| 88 | <para><function>glGetUniform</function> is available only if the |
| 89 | GL version is 2.0 or greater.</para> |
| 90 | |
| 91 | <para>If an error is generated, no change is made to the |
| 92 | contents of <parameter>params</parameter>.</para> |
| 93 | </refsect1> |
| 94 | <refsect1 id="errors"><title>Errors</title> |
| 95 | <para><constant>GL_INVALID_VALUE</constant> is generated if |
| 96 | <parameter>program</parameter> is not a value generated by |
| 97 | OpenGL.</para> |
| 98 | |
| 99 | <para><constant>GL_INVALID_OPERATION</constant> is generated if |
| 100 | <parameter>program</parameter> is not a program object.</para> |
| 101 | |
| 102 | <para><constant>GL_INVALID_OPERATION</constant> is generated if |
| 103 | <parameter>program</parameter> has not been successfully |
| 104 | linked.</para> |
| 105 | |
| 106 | <para><constant>GL_INVALID_OPERATION</constant> is generated if |
| 107 | <parameter>location</parameter> does not correspond to a valid |
| 108 | uniform variable location for the specified program object.</para> |
| 109 | |
| 110 | <para><constant>GL_INVALID_OPERATION</constant> is generated if |
| 111 | <function>glGetUniform</function> is executed between the |
| 112 | execution of |
| 113 | <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> |
| 114 | and the corresponding execution of |
| 115 | <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.</para> |
| 116 | </refsect1> |
| 117 | <refsect1 id="associatedgets"><title>Associated Gets</title> |
| 118 | <para><citerefentry><refentrytitle>glGetActiveUniform</refentrytitle></citerefentry> |
| 119 | with arguments <parameter>program</parameter> and the index of an active |
| 120 | uniform variable</para> |
| 121 | |
| 122 | <para><citerefentry><refentrytitle>glGetProgram</refentrytitle></citerefentry> |
| 123 | with arguments <parameter>program</parameter> and |
| 124 | <constant>GL_ACTIVE_UNIFORMS</constant> or |
| 125 | <constant>GL_ACTIVE_UNIFORM_MAX_LENGTH</constant></para> |
| 126 | |
| 127 | <para><citerefentry><refentrytitle>glGetUniformLocation</refentrytitle></citerefentry> |
| 128 | with arguments <parameter>program</parameter> and the name of a |
| 129 | uniform variable</para> |
| 130 | <para><citerefentry><refentrytitle>glIsProgram</refentrytitle></citerefentry></para> |
| 131 | </refsect1> |
| 132 | <refsect1 id="seealso"><title>See Also</title> |
| 133 | <para><citerefentry><refentrytitle>glCreateProgram</refentrytitle></citerefentry>, |
| 134 | <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry>, |
| 135 | <citerefentry><refentrytitle>glUniform</refentrytitle></citerefentry></para> |
| 136 | </refsect1> |
| 137 | <refsect1 id="Copyright"><title>Copyright</title> |
| 138 | <para> |
| 139 | Copyright <trademark class="copyright"></trademark> 2003-2005 3Dlabs Inc. Ltd. |
| 140 | This material may be distributed subject to the terms and conditions set forth in |
| 141 | the Open Publication License, v 1.0, 8 June 1999. |
| 142 | <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>. |
| 143 | </para> |
| 144 | </refsect1> |
| 145 | </refentry> |