[clinton/guile-figl.git] / upstream-doc / man2 / glGetTexEnv.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
              "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<refentry id="glGetTexEnv">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>1991-2006</year>
                <holder>Silicon Graphics, Inc.</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>glGetTexEnv</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glGetTexEnv</refname>
        <refpurpose>return texture environment parameters</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glGetTexEnvfv</function></funcdef>
                <paramdef>GLenum <parameter>target</parameter></paramdef>
                <paramdef>GLenum <parameter>pname</parameter></paramdef>
                <paramdef>GLfloat * <parameter>params</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
        <para></para>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glGetTexEnviv</function></funcdef>
                <paramdef>GLenum <parameter>target</parameter></paramdef>
                <paramdef>GLenum <parameter>pname</parameter></paramdef>
                <paramdef>GLint * <parameter>params</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>target</parameter></term>
            <listitem>
                <para>
                    Specifies a texture environment. May be
                    <constant>GL_TEXTURE_ENV</constant>,
                    <constant>GL_TEXTURE_FILTER_CONTROL</constant>, or
                    <constant>GL_POINT_SPRITE</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>pname</parameter></term>
            <listitem>
                <para>
                    Specifies the symbolic name of a texture environment parameter.
                    Accepted values are <constant>GL_TEXTURE_ENV_MODE</constant>, <constant>GL_TEXTURE_ENV_COLOR</constant>,
                    <constant>GL_TEXTURE_LOD_BIAS</constant>,
                    <constant>GL_COMBINE_RGB</constant>,
                    <constant>GL_COMBINE_ALPHA</constant>,
                    <constant>GL_SRC0_RGB</constant>,
                    <constant>GL_SRC1_RGB</constant>,
                    <constant>GL_SRC2_RGB</constant>,
                    <constant>GL_SRC0_ALPHA</constant>,
                    <constant>GL_SRC1_ALPHA</constant>,
                    <constant>GL_SRC2_ALPHA</constant>,
                    <constant>GL_OPERAND0_RGB</constant>,
                    <constant>GL_OPERAND1_RGB</constant>,
                    <constant>GL_OPERAND2_RGB</constant>,
                    <constant>GL_OPERAND0_ALPHA</constant>,
                    <constant>GL_OPERAND1_ALPHA</constant>,
                    <constant>GL_OPERAND2_ALPHA</constant>,
                    <constant>GL_RGB_SCALE</constant>,
                    <constant>GL_ALPHA_SCALE</constant>, or
                    <constant>GL_COORD_REPLACE</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>params</parameter></term>
            <listitem>
                <para>
                    Returns the requested data.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>glGetTexEnv</function> returns in <parameter>params</parameter> selected values of a texture environment that
            was specified with <citerefentry><refentrytitle>glTexEnv</refentrytitle></citerefentry>.
            <parameter>target</parameter> specifies a texture environment.
        </para>
        <para>
            When <parameter>target</parameter> is <constant>GL_TEXTURE_FILTER_CONTROL</constant>,
            <parameter>pname</parameter> must be <constant>GL_TEXTURE_LOD_BIAS</constant>.  
            When <parameter>target</parameter> is <constant>GL_POINT_SPRITE</constant>,
            <parameter>pname</parameter> must be <constant>GL_COORD_REPLACE</constant>.
            When <parameter>target</parameter> is
            <constant>GL_TEXTURE_ENV</constant>, <parameter>pname</parameter> can be <constant>GL_TEXTURE_ENV_MODE</constant>,
            <constant>GL_TEXTURE_ENV_COLOR</constant>, <constant>GL_COMBINE_RGB</constant>, <constant>GL_COMBINE_ALPHA</constant>,
            <constant>GL_RGB_SCALE</constant>, <constant>GL_ALPHA_SCALE</constant>, 
            <constant>GL_SRC0_RGB</constant>, <constant>GL_SRC1_RGB</constant>, <constant>GL_SRC2_RGB</constant>,
            <constant>GL_SRC0_ALPHA</constant>, <constant>GL_SRC1_ALPHA</constant>, or <constant>GL_SRC2_ALPHA</constant>.
        </para>
        <para>
            <parameter>pname</parameter> names a specific texture environment parameter, as follows:
        </para>
        <variablelist>
            <varlistentry>
                <term><constant>GL_TEXTURE_ENV_MODE</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns the single-valued texture environment mode,
                        a symbolic constant. The initial value is <constant>GL_MODULATE</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_TEXTURE_ENV_COLOR</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns four integer or floating-point values that are the
                        texture environment color.
                        Integer values,
                        when requested,
                        are linearly mapped from the internal floating-point representation
                        such that 1.0 maps to the most positive representable integer,
                        and 
                        <inlineequation><mml:math>
                            <!-- eqn: -1.0:-->
                            <mml:mn>-1.0</mml:mn>
                        </mml:math></inlineequation>
                        maps to the most negative representable integer. The initial
                        value is (0, 0, 0, 0).
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_TEXTURE_LOD_BIAS</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single floating-point value that is the texture
                        level-of-detail bias.  The initial value is 0.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_COMBINE_RGB</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the current
                        RGB combine mode.  The initial value is <constant>GL_MODULATE</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_COMBINE_ALPHA</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the current
                        alpha combine mode.  The initial value is <constant>GL_MODULATE</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_SRC0_RGB</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the texture
                        combiner zero's RGB source.  The initial value is <constant>GL_TEXTURE</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_SRC1_RGB</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the texture
                        combiner one's RGB source.  The initial value is <constant>GL_PREVIOUS</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_SRC2_RGB</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the texture
                        combiner two's RGB source.  The initial value is <constant>GL_CONSTANT</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_SRC0_ALPHA</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the texture
                        combiner zero's alpha source.  The initial value is <constant>GL_TEXTURE</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_SRC1_ALPHA</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the texture
                        combiner one's alpha source.  The initial value is <constant>GL_PREVIOUS</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_SRC2_ALPHA</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the texture
                        combiner two's alpha source.  The initial value is <constant>GL_CONSTANT</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_OPERAND0_RGB</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the texture
                        combiner zero's RGB operand.  The initial value is <constant>GL_SRC_COLOR</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_OPERAND1_RGB</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the texture
                        combiner one's RGB operand.  The initial value is <constant>GL_SRC_COLOR</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_OPERAND2_RGB</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the texture
                        combiner two's RGB operand.  The initial value is <constant>GL_SRC_ALPHA</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_OPERAND0_ALPHA</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the texture
                        combiner zero's alpha operand.  The initial value is <constant>GL_SRC_ALPHA</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_OPERAND1_ALPHA</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the texture
                        combiner one's alpha operand.  The initial value is <constant>GL_SRC_ALPHA</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_OPERAND2_ALPHA</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single symbolic constant value representing the texture
                        combiner two's alpha operand.  The initial value is <constant>GL_SRC_ALPHA</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_RGB_SCALE</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single floating-point value representing the current RGB
                        texture combiner scaling factor.  The initial value is 1.0.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_ALPHA_SCALE</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single floating-point value representing the current alpha
                        texture combiner scaling factor.  The initial value is 1.0.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_COORD_REPLACE</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a single boolean value representing the current point sprite
                        texture coordinate replacement enable state.  The initial value is <constant>GL_FALSE</constant>.
                    </para>
                </listitem>
            </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="notes"><title>Notes</title>
        <para>
            If an error is generated,
            no change is made to the contents of <parameter>params</parameter>.
        </para>
        <para>
            For OpenGL versions 1.3 and greater, or when the <code>ARB_multitexture</code> extension is supported, <function>glGetTexEnv</function> returns
            the texture environment parameters for the active texture unit.
        </para>
        <para>
            <constant>GL_COMBINE_RGB</constant>,
            <constant>GL_COMBINE_ALPHA</constant>,
            <constant>GL_SRC0_RGB</constant>,
            <constant>GL_SRC1_RGB</constant>,
            <constant>GL_SRC2_RGB</constant>,
            <constant>GL_SRC0_ALPHA</constant>,
            <constant>GL_SRC1_ALPHA</constant>,
            <constant>GL_SRC2_ALPHA</constant>,
            <constant>GL_OPERAND0_RGB</constant>,
            <constant>GL_OPERAND1_RGB</constant>,
            <constant>GL_OPERAND2_RGB</constant>,
            <constant>GL_OPERAND0_ALPHA</constant>,
            <constant>GL_OPERAND1_ALPHA</constant>,
            <constant>GL_OPERAND2_ALPHA</constant>,
            <constant>GL_RGB_SCALE</constant>, and
            <constant>GL_ALPHA_SCALE</constant> are available only if the GL version is 1.3 or greater.
        </para>
        <para>
            <constant>GL_TEXTURE_FILTER_CONTROL</constant> and <constant>GL_TEXTURE_LOD_BIAS</constant> are available
            only if the GL version is 1.4 or greater.
        </para>
        <para>
            <constant>GL_POINT_SPRITE</constant> and <constant>GL_COORD_REPLACE</constant> are available
            only if the GL version is 2.0 or greater.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> or <parameter>pname</parameter> is not an
            accepted value.
        </para>
        <para>
            <constant>GL_INVALID_OPERATION</constant> is generated if <function>glGetTexEnv</function>
            is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
            and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexEnv</refentrytitle></citerefentry>
        </para>
    </refsect1>
    <refsect1 id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"></trademark> 1991-2006
            Silicon Graphics, Inc. This document is licensed under the SGI
            Free Software B License. For details, see
            <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
        </para>
    </refsect1>
</refentry>
Commit	Line	Data
7faf1d71 AW	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="glGetTexEnv">
	5	<refmeta>
	6	<refmetainfo>
	7	<copyright>
	8	<year>1991-2006</year>
	9	<holder>Silicon Graphics, Inc.</holder>
	10	</copyright>
	11	</refmetainfo>
	12	<refentrytitle>glGetTexEnv</refentrytitle>
	13	<manvolnum>3G</manvolnum>
	14	</refmeta>
	15	<refnamediv>
	16	<refname>glGetTexEnv</refname>
	17	<refpurpose>return texture environment parameters</refpurpose>
	18	</refnamediv>
	19	<refsynopsisdiv><title>C Specification</title>
	20	<funcsynopsis>
	21	<funcprototype>
	22	<funcdef>void <function>glGetTexEnvfv</function></funcdef>
	23	<paramdef>GLenum <parameter>target</parameter></paramdef>
	24	<paramdef>GLenum <parameter>pname</parameter></paramdef>
	25	<paramdef>GLfloat * <parameter>params</parameter></paramdef>
	26	</funcprototype>
	27	</funcsynopsis>
	28	<para></para>
	29	<funcsynopsis>
	30	<funcprototype>
	31	<funcdef>void <function>glGetTexEnviv</function></funcdef>
	32	<paramdef>GLenum <parameter>target</parameter></paramdef>
	33	<paramdef>GLenum <parameter>pname</parameter></paramdef>
	34	<paramdef>GLint * <parameter>params</parameter></paramdef>
	35	</funcprototype>
	36	</funcsynopsis>
	37	</refsynopsisdiv>
	38	<refsect1 id="parameters"><title>Parameters</title>
	39	<variablelist>
	40	<varlistentry>
	41	<term><parameter>target</parameter></term>
	42	<listitem>
	43	<para>
	44	Specifies a texture environment. May be
	45	<constant>GL_TEXTURE_ENV</constant>,
	46	<constant>GL_TEXTURE_FILTER_CONTROL</constant>, or
	47	<constant>GL_POINT_SPRITE</constant>.
	48	</para>
	49	</listitem>
	50	</varlistentry>
	51	<varlistentry>
	52	<term><parameter>pname</parameter></term>
	53	<listitem>
	54	<para>
	55	Specifies the symbolic name of a texture environment parameter.
	56	Accepted values are <constant>GL_TEXTURE_ENV_MODE</constant>, <constant>GL_TEXTURE_ENV_COLOR</constant>,
	57	<constant>GL_TEXTURE_LOD_BIAS</constant>,
	58	<constant>GL_COMBINE_RGB</constant>,
	59	<constant>GL_COMBINE_ALPHA</constant>,
	60	<constant>GL_SRC0_RGB</constant>,
	61	<constant>GL_SRC1_RGB</constant>,
	62	<constant>GL_SRC2_RGB</constant>,
	63	<constant>GL_SRC0_ALPHA</constant>,
	64	<constant>GL_SRC1_ALPHA</constant>,
65	<constant>GL_SRC2_ALPHA</constant>,
66	<constant>GL_OPERAND0_RGB</constant>,
67	<constant>GL_OPERAND1_RGB</constant>,
68	<constant>GL_OPERAND2_RGB</constant>,
69	<constant>GL_OPERAND0_ALPHA</constant>,
70	<constant>GL_OPERAND1_ALPHA</constant>,
71	<constant>GL_OPERAND2_ALPHA</constant>,
72	<constant>GL_RGB_SCALE</constant>,
73	<constant>GL_ALPHA_SCALE</constant>, or
74	<constant>GL_COORD_REPLACE</constant>.
75	</para>
76	</listitem>
77	</varlistentry>
78	<varlistentry>
79	<term><parameter>params</parameter></term>
80	<listitem>
81	<para>
82	Returns the requested data.
83	</para>
84	</listitem>
85	</varlistentry>
86	</variablelist>
87	</refsect1>
88	<refsect1 id="description"><title>Description</title>
89	<para>
90	<function>glGetTexEnv</function> returns in <parameter>params</parameter> selected values of a texture environment that
91	was specified with <citerefentry><refentrytitle>glTexEnv</refentrytitle></citerefentry>.
92	<parameter>target</parameter> specifies a texture environment.
93	</para>
94	<para>
95	When <parameter>target</parameter> is <constant>GL_TEXTURE_FILTER_CONTROL</constant>,
96	<parameter>pname</parameter> must be <constant>GL_TEXTURE_LOD_BIAS</constant>.
97	When <parameter>target</parameter> is <constant>GL_POINT_SPRITE</constant>,
98	<parameter>pname</parameter> must be <constant>GL_COORD_REPLACE</constant>.
99	When <parameter>target</parameter> is
100	<constant>GL_TEXTURE_ENV</constant>, <parameter>pname</parameter> can be <constant>GL_TEXTURE_ENV_MODE</constant>,
101	<constant>GL_TEXTURE_ENV_COLOR</constant>, <constant>GL_COMBINE_RGB</constant>, <constant>GL_COMBINE_ALPHA</constant>,
102	<constant>GL_RGB_SCALE</constant>, <constant>GL_ALPHA_SCALE</constant>,
103	<constant>GL_SRC0_RGB</constant>, <constant>GL_SRC1_RGB</constant>, <constant>GL_SRC2_RGB</constant>,
104	<constant>GL_SRC0_ALPHA</constant>, <constant>GL_SRC1_ALPHA</constant>, or <constant>GL_SRC2_ALPHA</constant>.
105	</para>
106	<para>
107	<parameter>pname</parameter> names a specific texture environment parameter, as follows:
108	</para>
109	<variablelist>
110	<varlistentry>
111	<term><constant>GL_TEXTURE_ENV_MODE</constant></term>
112	<listitem>
113	<para>
114	<parameter>params</parameter> returns the single-valued texture environment mode,
115	a symbolic constant. The initial value is <constant>GL_MODULATE</constant>.
116	</para>
117	</listitem>
118	</varlistentry>
119	<varlistentry>
120	<term><constant>GL_TEXTURE_ENV_COLOR</constant></term>
121	<listitem>
122	<para>
123	<parameter>params</parameter> returns four integer or floating-point values that are the
124	texture environment color.
125	Integer values,
126	when requested,
127	are linearly mapped from the internal floating-point representation
128	such that 1.0 maps to the most positive representable integer,
129	and
130	<inlineequation><mml:math>
131	<!-- eqn: -1.0:-->
132	<mml:mn>-1.0</mml:mn>
133	</mml:math></inlineequation>
134	maps to the most negative representable integer. The initial
135	value is (0, 0, 0, 0).
136	</para>
137	</listitem>
138	</varlistentry>
139	<varlistentry>
140	<term><constant>GL_TEXTURE_LOD_BIAS</constant></term>
141	<listitem>
142	<para>
143	<parameter>params</parameter> returns a single floating-point value that is the texture
144	level-of-detail bias. The initial value is 0.
145	</para>
146	</listitem>
147	</varlistentry>
148	<varlistentry>
149	<term><constant>GL_COMBINE_RGB</constant></term>
150	<listitem>
151	<para>
152	<parameter>params</parameter> returns a single symbolic constant value representing the current
153	RGB combine mode. The initial value is <constant>GL_MODULATE</constant>.
154	</para>
155	</listitem>
156	</varlistentry>
157	<varlistentry>
158	<term><constant>GL_COMBINE_ALPHA</constant></term>
159	<listitem>
160	<para>
161	<parameter>params</parameter> returns a single symbolic constant value representing the current
162	alpha combine mode. The initial value is <constant>GL_MODULATE</constant>.
163	</para>
164	</listitem>
165	</varlistentry>
166	<varlistentry>
167	<term><constant>GL_SRC0_RGB</constant></term>
168	<listitem>
169	<para>
170	<parameter>params</parameter> returns a single symbolic constant value representing the texture
171	combiner zero's RGB source. The initial value is <constant>GL_TEXTURE</constant>.
172	</para>
173	</listitem>
174	</varlistentry>
175	<varlistentry>
176	<term><constant>GL_SRC1_RGB</constant></term>
177	<listitem>
178	<para>
179	<parameter>params</parameter> returns a single symbolic constant value representing the texture
180	combiner one's RGB source. The initial value is <constant>GL_PREVIOUS</constant>.
181	</para>
182	</listitem>
183	</varlistentry>
184	<varlistentry>
185	<term><constant>GL_SRC2_RGB</constant></term>
186	<listitem>
187	<para>
188	<parameter>params</parameter> returns a single symbolic constant value representing the texture
189	combiner two's RGB source. The initial value is <constant>GL_CONSTANT</constant>.
190	</para>
191	</listitem>
192	</varlistentry>
193	<varlistentry>
194	<term><constant>GL_SRC0_ALPHA</constant></term>
195	<listitem>
196	<para>
197	<parameter>params</parameter> returns a single symbolic constant value representing the texture
198	combiner zero's alpha source. The initial value is <constant>GL_TEXTURE</constant>.
199	</para>
200	</listitem>
201	</varlistentry>
202	<varlistentry>
203	<term><constant>GL_SRC1_ALPHA</constant></term>
204	<listitem>
205	<para>
206	<parameter>params</parameter> returns a single symbolic constant value representing the texture
207	combiner one's alpha source. The initial value is <constant>GL_PREVIOUS</constant>.
208	</para>
209	</listitem>
210	</varlistentry>
211	<varlistentry>
212	<term><constant>GL_SRC2_ALPHA</constant></term>
213	<listitem>
214	<para>
215	<parameter>params</parameter> returns a single symbolic constant value representing the texture
216	combiner two's alpha source. The initial value is <constant>GL_CONSTANT</constant>.
217	</para>
218	</listitem>
219	</varlistentry>
220	<varlistentry>
221	<term><constant>GL_OPERAND0_RGB</constant></term>
222	<listitem>
223	<para>
224	<parameter>params</parameter> returns a single symbolic constant value representing the texture
225	combiner zero's RGB operand. The initial value is <constant>GL_SRC_COLOR</constant>.
226	</para>
227	</listitem>
228	</varlistentry>
229	<varlistentry>
230	<term><constant>GL_OPERAND1_RGB</constant></term>
231	<listitem>
232	<para>
233	<parameter>params</parameter> returns a single symbolic constant value representing the texture
234	combiner one's RGB operand. The initial value is <constant>GL_SRC_COLOR</constant>.
235	</para>
236	</listitem>
237	</varlistentry>
238	<varlistentry>
239	<term><constant>GL_OPERAND2_RGB</constant></term>
240	<listitem>
241	<para>
242	<parameter>params</parameter> returns a single symbolic constant value representing the texture
243	combiner two's RGB operand. The initial value is <constant>GL_SRC_ALPHA</constant>.
244	</para>
245	</listitem>
246	</varlistentry>
247	<varlistentry>
248	<term><constant>GL_OPERAND0_ALPHA</constant></term>
249	<listitem>
250	<para>
251	<parameter>params</parameter> returns a single symbolic constant value representing the texture
252	combiner zero's alpha operand. The initial value is <constant>GL_SRC_ALPHA</constant>.
253	</para>
254	</listitem>
255	</varlistentry>
256	<varlistentry>
257	<term><constant>GL_OPERAND1_ALPHA</constant></term>
258	<listitem>
259	<para>
260	<parameter>params</parameter> returns a single symbolic constant value representing the texture
261	combiner one's alpha operand. The initial value is <constant>GL_SRC_ALPHA</constant>.
262	</para>
263	</listitem>
264	</varlistentry>
265	<varlistentry>
266	<term><constant>GL_OPERAND2_ALPHA</constant></term>
267	<listitem>
268	<para>
269	<parameter>params</parameter> returns a single symbolic constant value representing the texture
270	combiner two's alpha operand. The initial value is <constant>GL_SRC_ALPHA</constant>.
271	</para>
272	</listitem>
273	</varlistentry>
274	<varlistentry>
275	<term><constant>GL_RGB_SCALE</constant></term>
276	<listitem>
277	<para>
278	<parameter>params</parameter> returns a single floating-point value representing the current RGB
279	texture combiner scaling factor. The initial value is 1.0.
280	</para>
281	</listitem>
282	</varlistentry>
283	<varlistentry>
284	<term><constant>GL_ALPHA_SCALE</constant></term>
285	<listitem>
286	<para>
287	<parameter>params</parameter> returns a single floating-point value representing the current alpha
288	texture combiner scaling factor. The initial value is 1.0.
289	</para>
290	</listitem>
291	</varlistentry>
292	<varlistentry>
293	<term><constant>GL_COORD_REPLACE</constant></term>
294	<listitem>
295	<para>
296	<parameter>params</parameter> returns a single boolean value representing the current point sprite
297	texture coordinate replacement enable state. The initial value is <constant>GL_FALSE</constant>.
298	</para>
299	</listitem>
300	</varlistentry>
301	</variablelist>
302	</refsect1>
303	<refsect1 id="notes"><title>Notes</title>
304	<para>
305	If an error is generated,
306	no change is made to the contents of <parameter>params</parameter>.
307	</para>
308	<para>
309	For OpenGL versions 1.3 and greater, or when the <code>ARB_multitexture</code> extension is supported, <function>glGetTexEnv</function> returns
310	the texture environment parameters for the active texture unit.
311	</para>
312	<para>
313	<constant>GL_COMBINE_RGB</constant>,
314	<constant>GL_COMBINE_ALPHA</constant>,
315	<constant>GL_SRC0_RGB</constant>,
316	<constant>GL_SRC1_RGB</constant>,
317	<constant>GL_SRC2_RGB</constant>,
318	<constant>GL_SRC0_ALPHA</constant>,
319	<constant>GL_SRC1_ALPHA</constant>,
320	<constant>GL_SRC2_ALPHA</constant>,
321	<constant>GL_OPERAND0_RGB</constant>,
322	<constant>GL_OPERAND1_RGB</constant>,
323	<constant>GL_OPERAND2_RGB</constant>,
324	<constant>GL_OPERAND0_ALPHA</constant>,
325	<constant>GL_OPERAND1_ALPHA</constant>,
326	<constant>GL_OPERAND2_ALPHA</constant>,
327	<constant>GL_RGB_SCALE</constant>, and
328	<constant>GL_ALPHA_SCALE</constant> are available only if the GL version is 1.3 or greater.
329	</para>
330	<para>
331	<constant>GL_TEXTURE_FILTER_CONTROL</constant> and <constant>GL_TEXTURE_LOD_BIAS</constant> are available
332	only if the GL version is 1.4 or greater.
333	</para>
334	<para>
335	<constant>GL_POINT_SPRITE</constant> and <constant>GL_COORD_REPLACE</constant> are available
336	only if the GL version is 2.0 or greater.
337	</para>
338	</refsect1>
339	<refsect1 id="errors"><title>Errors</title>
340	<para>
341	<constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> or <parameter>pname</parameter> is not an
342	accepted value.
343	</para>
344	<para>
345	<constant>GL_INVALID_OPERATION</constant> is generated if <function>glGetTexEnv</function>
346	is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
347	and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
348	</para>
349	</refsect1>
350	<refsect1 id="seealso"><title>See Also</title>
351	<para>
352	<citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>,
353	<citerefentry><refentrytitle>glTexEnv</refentrytitle></citerefentry>
354	</para>
355	</refsect1>
356	<refsect1 id="Copyright"><title>Copyright</title>
357	<para>
358	Copyright <trademark class="copyright"></trademark> 1991-2006
359	Silicon Graphics, Inc. This document is licensed under the SGI
360	Free Software B License. For details, see
361	<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
362	</para>
363	</refsect1>
364	</refentry>