[clinton/guile-figl.git] / upstream-doc / man4 / glStencilOpSeparate.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="glStencilOpSeparate">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>1991-2006</year>
                <holder>Silicon Graphics, Inc.</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>glStencilOpSeparate</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glStencilOpSeparate</refname>
        <refpurpose>set front and/or back stencil test actions</refpurpose>
    </refnamediv>
    <!-- eqn: ignoring delim $$ -->
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glStencilOpSeparate</function></funcdef>
                <paramdef>GLenum <parameter>face</parameter></paramdef>
                <paramdef>GLenum <parameter>sfail</parameter></paramdef>
                <paramdef>GLenum <parameter>dpfail</parameter></paramdef>
                <paramdef>GLenum <parameter>dppass</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>face</parameter></term>
            <listitem>
                <para>
                    Specifies whether front and/or back stencil state is updated.
                    Three symbolic constants are valid:
                    <constant>GL_FRONT</constant>,
                    <constant>GL_BACK</constant>, and
                    <constant>GL_FRONT_AND_BACK</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>sfail</parameter></term>
            <listitem>
                <para>
                    Specifies the action to take when the stencil test fails.
                    Eight symbolic constants are accepted:
                    <constant>GL_KEEP</constant>,
                    <constant>GL_ZERO</constant>,
                    <constant>GL_REPLACE</constant>,
                    <constant>GL_INCR</constant>,
                    <constant>GL_INCR_WRAP</constant>,
                    <constant>GL_DECR</constant>,
                    <constant>GL_DECR_WRAP</constant>, and
                    <constant>GL_INVERT</constant>. The initial value is <constant>GL_KEEP</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>dpfail</parameter></term>
            <listitem>
                <para>
                    Specifies the stencil action when the stencil test passes,
                    but the depth test fails.
                    <parameter>dpfail</parameter> accepts the same symbolic constants as <parameter>sfail</parameter>. The initial value
                    is <constant>GL_KEEP</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>dppass</parameter></term>
            <listitem>
                <para>
                    Specifies the stencil action when both the stencil test and the depth
                    test pass, or when the stencil test passes and either there is no
                    depth buffer or depth testing is not enabled.
                    <parameter>dppass</parameter> accepts the same symbolic constants as <parameter>sfail</parameter>. The initial value
                    is <constant>GL_KEEP</constant>.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            Stenciling,
            like depth-buffering,
            enables and disables drawing on a per-pixel basis.
            You draw into the stencil planes using GL drawing primitives,
            then render geometry and images,
            using the stencil planes to mask out portions of the screen.
            Stenciling is typically used in multipass rendering algorithms
            to achieve special effects,
            such as decals,
            outlining,
            and constructive solid geometry rendering.
        </para>
        <para>
            The stencil test conditionally eliminates a pixel based on the outcome
            of a comparison between the value in the stencil buffer and a
            reference value. To enable and disable the test, call <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>
            and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> with argument
            <constant>GL_STENCIL_TEST</constant>; to control it, call 
            <citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry> or 
            <citerefentry><refentrytitle>glStencilFuncSeparate</refentrytitle></citerefentry>.
        </para>
        <para>
            There can be two separate sets of <parameter>sfail</parameter>, <parameter>dpfail</parameter>, and 
            <parameter>dppass</parameter> parameters; one affects back-facing polygons, and the other
            affects front-facing polygons as well as other non-polygon primitives. 
            <citerefentry><refentrytitle>glStencilOp</refentrytitle></citerefentry> sets both front
            and back stencil state to the same values, as if 
            <citerefentry><refentrytitle>glStencilOpSeparate</refentrytitle></citerefentry> were called
            with <parameter>face</parameter> set to <constant>GL_FRONT_AND_BACK</constant>.
        </para>
        <para>
            <function>glStencilOpSeparate</function> takes three arguments that indicate what happens
            to the stored stencil value while stenciling is enabled.
            If the stencil test fails,
            no change is made to the pixel's color or depth buffers,
            and <parameter>sfail</parameter> specifies what happens to the stencil buffer contents.
            The following eight actions are possible.
        </para>
        <variablelist>
            <varlistentry>
                <term><constant>GL_KEEP</constant></term>
                <listitem>
                    <para>
                        Keeps the current value.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_ZERO</constant></term>
                <listitem>
                    <para>
                        Sets the stencil buffer value to 0.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_REPLACE</constant></term>
                <listitem>
                    <para>
                        Sets the stencil buffer value to <emphasis>ref</emphasis>,
                        as specified by <citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_INCR</constant></term>
                <listitem>
                    <para>
                        Increments the current stencil buffer value.
                        Clamps to the maximum representable unsigned value.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_INCR_WRAP</constant></term>
                <listitem>
                    <para>
                        Increments the current stencil buffer value.
                        Wraps stencil buffer value to zero when incrementing the maximum
                        representable unsigned value.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_DECR</constant></term>
                <listitem>
                    <para>
                        Decrements the current stencil buffer value.
                        Clamps to 0.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_DECR_WRAP</constant></term>
                <listitem>
                    <para>
                        Decrements the current stencil buffer value.
                        Wraps stencil buffer value to the maximum representable unsigned value when
                        decrementing a stencil buffer value of zero.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_INVERT</constant></term>
                <listitem>
                    <para>
                        Bitwise inverts the current stencil buffer value.
                    </para>
                </listitem>
            </varlistentry>
        </variablelist>
        <para>
            Stencil buffer values are treated as unsigned integers.
            When incremented and decremented,
            values are clamped to 0 and 
            <inlineequation><mml:math>
                <!-- eqn: 2 sup n - 1:-->
                <mml:mrow>
                    <mml:msup><mml:mn>2</mml:mn>
                    <mml:mi mathvariant="italic">n</mml:mi>
                    </mml:msup>
                    <mml:mo>-</mml:mo>
                    <mml:mn>1</mml:mn>
                </mml:mrow>
            </mml:math></inlineequation>,
            where 
            <inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>
            is the value returned by querying <constant>GL_STENCIL_BITS</constant>.
        </para>
        <para>
            The other two arguments to <function>glStencilOpSeparate</function> specify stencil buffer actions
            that depend on whether subsequent depth buffer tests succeed (<parameter>dppass</parameter>)
            or fail (<parameter>dpfail</parameter>) (see
            <citerefentry><refentrytitle>glDepthFunc</refentrytitle></citerefentry>).
            The actions are specified using the same eight symbolic constants as <parameter>sfail</parameter>.
            Note that <parameter>dpfail</parameter> is ignored when there is no depth buffer,
            or when the depth buffer is not enabled.
            In these cases, <parameter>sfail</parameter> and <parameter>dppass</parameter> specify stencil action when the
            stencil test fails and passes,
            respectively.
        </para>
    </refsect1>
    <refsect1 id="notes"><title>Notes</title>
        <para>
            Initially the stencil test is disabled.
            If there is no stencil buffer,
            no stencil modification can occur
            and it is as if the stencil test always passes.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>face</parameter> is any value 
            other than <constant>GL_FRONT</constant>, <constant>GL_BACK</constant>, or <constant>GL_FRONT_AND_BACK</constant>.
        </para>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>sfail</parameter>,
            <parameter>dpfail</parameter>, or <parameter>dppass</parameter> is any value other than the eight defined constant values.
        </para>
    </refsect1>
    <refsect1 id="associatedgets"><title>Associated Gets</title>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument 
            <constant>GL_STENCIL_FAIL</constant>, <constant>GL_STENCIL_PASS_DEPTH_PASS</constant>, 
            <constant>GL_STENCIL_PASS_DEPTH_FAIL</constant>, <constant>GL_STENCIL_BACK_FAIL</constant>, 
            <constant>GL_STENCIL_BACK_PASS_DEPTH_PASS</constant>, <constant>GL_STENCIL_BACK_PASS_DEPTH_FAIL</constant>,
            or <constant>GL_STENCIL_BITS</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_STENCIL_TEST</constant>
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glDepthFunc</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glLogicOp</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glStencilFuncSeparate</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glStencilMask</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glStencilMaskSeparate</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glStencilOp</refentrytitle></citerefentry>
        </para>
    </refsect1>
    <refsect1 id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"></trademark> 2006 Khronos Group. 
            This material may be distributed subject to the terms and conditions set forth in 
            the Open Publication License, v 1.0, 8 June 1999.
            <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</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="glStencilOpSeparate">
	5	<refmeta>
	6	<refmetainfo>
	7	<copyright>
	8	<year>1991-2006</year>
	9	<holder>Silicon Graphics, Inc.</holder>
	10	</copyright>
	11	</refmetainfo>
	12	<refentrytitle>glStencilOpSeparate</refentrytitle>
	13	<manvolnum>3G</manvolnum>
	14	</refmeta>
	15	<refnamediv>
	16	<refname>glStencilOpSeparate</refname>
	17	<refpurpose>set front and/or back stencil test actions</refpurpose>
	18	</refnamediv>
	19	<!-- eqn: ignoring delim $$ -->
	20	<refsynopsisdiv><title>C Specification</title>
	21	<funcsynopsis>
	22	<funcprototype>
	23	<funcdef>void <function>glStencilOpSeparate</function></funcdef>
	24	<paramdef>GLenum <parameter>face</parameter></paramdef>
	25	<paramdef>GLenum <parameter>sfail</parameter></paramdef>
	26	<paramdef>GLenum <parameter>dpfail</parameter></paramdef>
	27	<paramdef>GLenum <parameter>dppass</parameter></paramdef>
	28	</funcprototype>
	29	</funcsynopsis>
	30	</refsynopsisdiv>
	31	<refsect1 id="parameters"><title>Parameters</title>
	32	<variablelist>
	33	<varlistentry>
	34	<term><parameter>face</parameter></term>
	35	<listitem>
	36	<para>
	37	Specifies whether front and/or back stencil state is updated.
	38	Three symbolic constants are valid:
	39	<constant>GL_FRONT</constant>,
	40	<constant>GL_BACK</constant>, and
	41	<constant>GL_FRONT_AND_BACK</constant>.
	42	</para>
	43	</listitem>
	44	</varlistentry>
	45	<varlistentry>
	46	<term><parameter>sfail</parameter></term>
	47	<listitem>
	48	<para>
	49	Specifies the action to take when the stencil test fails.
	50	Eight symbolic constants are accepted:
	51	<constant>GL_KEEP</constant>,
	52	<constant>GL_ZERO</constant>,
	53	<constant>GL_REPLACE</constant>,
	54	<constant>GL_INCR</constant>,
	55	<constant>GL_INCR_WRAP</constant>,
	56	<constant>GL_DECR</constant>,
	57	<constant>GL_DECR_WRAP</constant>, and
	58	<constant>GL_INVERT</constant>. The initial value is <constant>GL_KEEP</constant>.
	59	</para>
	60	</listitem>
	61	</varlistentry>
	62	<varlistentry>
	63	<term><parameter>dpfail</parameter></term>
	64	<listitem>
65	<para>
66	Specifies the stencil action when the stencil test passes,
67	but the depth test fails.
68	<parameter>dpfail</parameter> accepts the same symbolic constants as <parameter>sfail</parameter>. The initial value
69	is <constant>GL_KEEP</constant>.
70	</para>
71	</listitem>
72	</varlistentry>
73	<varlistentry>
74	<term><parameter>dppass</parameter></term>
75	<listitem>
76	<para>
77	Specifies the stencil action when both the stencil test and the depth
78	test pass, or when the stencil test passes and either there is no
79	depth buffer or depth testing is not enabled.
80	<parameter>dppass</parameter> accepts the same symbolic constants as <parameter>sfail</parameter>. The initial value
81	is <constant>GL_KEEP</constant>.
82	</para>
83	</listitem>
84	</varlistentry>
85	</variablelist>
86	</refsect1>
87	<refsect1 id="description"><title>Description</title>
88	<para>
89	Stenciling,
90	like depth-buffering,
91	enables and disables drawing on a per-pixel basis.
92	You draw into the stencil planes using GL drawing primitives,
93	then render geometry and images,
94	using the stencil planes to mask out portions of the screen.
95	Stenciling is typically used in multipass rendering algorithms
96	to achieve special effects,
97	such as decals,
98	outlining,
99	and constructive solid geometry rendering.
100	</para>
101	<para>
102	The stencil test conditionally eliminates a pixel based on the outcome
103	of a comparison between the value in the stencil buffer and a
104	reference value. To enable and disable the test, call <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>
105	and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> with argument
106	<constant>GL_STENCIL_TEST</constant>; to control it, call
107	<citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry> or
108	<citerefentry><refentrytitle>glStencilFuncSeparate</refentrytitle></citerefentry>.
109	</para>
110	<para>
111	There can be two separate sets of <parameter>sfail</parameter>, <parameter>dpfail</parameter>, and
112	<parameter>dppass</parameter> parameters; one affects back-facing polygons, and the other
113	affects front-facing polygons as well as other non-polygon primitives.
114	<citerefentry><refentrytitle>glStencilOp</refentrytitle></citerefentry> sets both front
115	and back stencil state to the same values, as if
116	<citerefentry><refentrytitle>glStencilOpSeparate</refentrytitle></citerefentry> were called
117	with <parameter>face</parameter> set to <constant>GL_FRONT_AND_BACK</constant>.
118	</para>
119	<para>
120	<function>glStencilOpSeparate</function> takes three arguments that indicate what happens
121	to the stored stencil value while stenciling is enabled.
122	If the stencil test fails,
123	no change is made to the pixel's color or depth buffers,
124	and <parameter>sfail</parameter> specifies what happens to the stencil buffer contents.
125	The following eight actions are possible.
126	</para>
127	<variablelist>
128	<varlistentry>
129	<term><constant>GL_KEEP</constant></term>
130	<listitem>
131	<para>
132	Keeps the current value.
133	</para>
134	</listitem>
135	</varlistentry>
136	<varlistentry>
137	<term><constant>GL_ZERO</constant></term>
138	<listitem>
139	<para>
140	Sets the stencil buffer value to 0.
141	</para>
142	</listitem>
143	</varlistentry>
144	<varlistentry>
145	<term><constant>GL_REPLACE</constant></term>
146	<listitem>
147	<para>
148	Sets the stencil buffer value to <emphasis>ref</emphasis>,
149	as specified by <citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry>.
150	</para>
151	</listitem>
152	</varlistentry>
153	<varlistentry>
154	<term><constant>GL_INCR</constant></term>
155	<listitem>
156	<para>
157	Increments the current stencil buffer value.
158	Clamps to the maximum representable unsigned value.
159	</para>
160	</listitem>
161	</varlistentry>
162	<varlistentry>
163	<term><constant>GL_INCR_WRAP</constant></term>
164	<listitem>
165	<para>
166	Increments the current stencil buffer value.
167	Wraps stencil buffer value to zero when incrementing the maximum
168	representable unsigned value.
169	</para>
170	</listitem>
171	</varlistentry>
172	<varlistentry>
173	<term><constant>GL_DECR</constant></term>
174	<listitem>
175	<para>
176	Decrements the current stencil buffer value.
177	Clamps to 0.
178	</para>
179	</listitem>
180	</varlistentry>
181	<varlistentry>
182	<term><constant>GL_DECR_WRAP</constant></term>
183	<listitem>
184	<para>
185	Decrements the current stencil buffer value.
186	Wraps stencil buffer value to the maximum representable unsigned value when
187	decrementing a stencil buffer value of zero.
188	</para>
189	</listitem>
190	</varlistentry>
191	<varlistentry>
192	<term><constant>GL_INVERT</constant></term>
193	<listitem>
194	<para>
195	Bitwise inverts the current stencil buffer value.
196	</para>
197	</listitem>
198	</varlistentry>
199	</variablelist>
200	<para>
201	Stencil buffer values are treated as unsigned integers.
202	When incremented and decremented,
203	values are clamped to 0 and
204	<inlineequation><mml:math>
205	<!-- eqn: 2 sup n - 1:-->
206	<mml:mrow>
207	<mml:msup><mml:mn>2</mml:mn>
208	<mml:mi mathvariant="italic">n</mml:mi>
209	</mml:msup>
210	<mml:mo>-</mml:mo>
211	<mml:mn>1</mml:mn>
212	</mml:mrow>
213	</mml:math></inlineequation>,
214	where
215	<inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>
216	is the value returned by querying <constant>GL_STENCIL_BITS</constant>.
217	</para>
218	<para>
219	The other two arguments to <function>glStencilOpSeparate</function> specify stencil buffer actions
220	that depend on whether subsequent depth buffer tests succeed (<parameter>dppass</parameter>)
221	or fail (<parameter>dpfail</parameter>) (see
222	<citerefentry><refentrytitle>glDepthFunc</refentrytitle></citerefentry>).
223	The actions are specified using the same eight symbolic constants as <parameter>sfail</parameter>.
224	Note that <parameter>dpfail</parameter> is ignored when there is no depth buffer,
225	or when the depth buffer is not enabled.
226	In these cases, <parameter>sfail</parameter> and <parameter>dppass</parameter> specify stencil action when the
227	stencil test fails and passes,
228	respectively.
229	</para>
230	</refsect1>
231	<refsect1 id="notes"><title>Notes</title>
232	<para>
233	Initially the stencil test is disabled.
234	If there is no stencil buffer,
235	no stencil modification can occur
236	and it is as if the stencil test always passes.
237	</para>
238	</refsect1>
239	<refsect1 id="errors"><title>Errors</title>
240	<para>
241	<constant>GL_INVALID_ENUM</constant> is generated if <parameter>face</parameter> is any value
242	other than <constant>GL_FRONT</constant>, <constant>GL_BACK</constant>, or <constant>GL_FRONT_AND_BACK</constant>.
243	</para>
244	<para>
245	<constant>GL_INVALID_ENUM</constant> is generated if <parameter>sfail</parameter>,
246	<parameter>dpfail</parameter>, or <parameter>dppass</parameter> is any value other than the eight defined constant values.
247	</para>
248	</refsect1>
249	<refsect1 id="associatedgets"><title>Associated Gets</title>
250	<para>
251	<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument
252	<constant>GL_STENCIL_FAIL</constant>, <constant>GL_STENCIL_PASS_DEPTH_PASS</constant>,
253	<constant>GL_STENCIL_PASS_DEPTH_FAIL</constant>, <constant>GL_STENCIL_BACK_FAIL</constant>,
254	<constant>GL_STENCIL_BACK_PASS_DEPTH_PASS</constant>, <constant>GL_STENCIL_BACK_PASS_DEPTH_FAIL</constant>,
255	or <constant>GL_STENCIL_BITS</constant>
256	</para>
257	<para>
258	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_STENCIL_TEST</constant>
259	</para>
260	</refsect1>
261	<refsect1 id="seealso"><title>See Also</title>
262	<para>
263	<citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>,
264	<citerefentry><refentrytitle>glDepthFunc</refentrytitle></citerefentry>,
265	<citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>,
266	<citerefentry><refentrytitle>glLogicOp</refentrytitle></citerefentry>,
267	<citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry>,
268	<citerefentry><refentrytitle>glStencilFuncSeparate</refentrytitle></citerefentry>,
269	<citerefentry><refentrytitle>glStencilMask</refentrytitle></citerefentry>,
270	<citerefentry><refentrytitle>glStencilMaskSeparate</refentrytitle></citerefentry>,
271	<citerefentry><refentrytitle>glStencilOp</refentrytitle></citerefentry>
272	</para>
273	</refsect1>
274	<refsect1 id="Copyright"><title>Copyright</title>
275	<para>
276	Copyright <trademark class="copyright"></trademark> 2006 Khronos Group.
277	This material may be distributed subject to the terms and conditions set forth in
278	the Open Publication License, v 1.0, 8 June 1999.
279	<ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
280	</para>
281	</refsect1>
282	</refentry>