[clinton/guile-figl.git] / upstream-doc / manglsl / gl_FrontFacing.xml

<?xml version="1.0" encoding="UTF-8"?>\r
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"\r
              "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">\r
<refentry id="gl_FrontFacing">\r
    <refmeta>\r
        <refmetainfo>\r
            <copyright>\r
                <year>2011</year>\r
                <holder>Khronos Group</holder>\r
            </copyright>\r
        </refmetainfo>\r
        <refentrytitle>gl_FrontFacing</refentrytitle>\r
        <manvolnum>3G</manvolnum>\r
    </refmeta>\r
    <refnamediv>\r
        <refname>gl_FrontFacing</refname>\r
        <refpurpose>indicates whether a primitive is front or back facing</refpurpose>\r
    </refnamediv>\r
    <refsynopsisdiv><title>Declaration</title>\r
        <funcsynopsis>\r
            <function>in bool gl_FrontFacing;</function>\r
        </funcsynopsis>\r
    </refsynopsisdiv>\r
    <refsect1 id="description"><title>Description</title>\r
        <para>\r
            Available only in the fragment language, <function>gl_FrontFacing</function> is an input variable\r
            whose value is <function>true</function> if the fragment belongs to a front-facing primitive and\r
            false otherwise. The determination of whether a triangle primitive is front-facing is made by\r
            examining the sign of the area of the triangle, including a possible reversal of this sign\r
            as controlled by <function>glFrontFace</function>. One way to compute this area is:\r
        </para>\r
        <para>\r
            <inlineequation><mml:math>\r
                <mml:mi>a</mml:mi><mml:mo>=</mml:mo><mml:mfrac><mml:mrow><mml:mn>1</mml:mn></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:mfrac>\r
                <mml:msubsup><mml:mo>&#x2211;</mml:mo><mml:mrow>\r
                    <mml:mi>j</mml:mi><mml:mo>=</mml:mo><mml:mn>0</mml:mn>\r
                </mml:mrow>\r
                <mml:mrow>\r
                    <mml:mi>n</mml:mi><mml:mo>-</mml:mo><mml:mn>1</mml:mn>\r
                </mml:mrow></mml:msubsup>\r
                <mml:msubsup><mml:mi>x</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msubsup>\r
                <mml:msubsup><mml:mi>y</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msubsup>\r
                <mml:mo>-</mml:mo>\r
                <mml:msubsup><mml:mi>x</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msubsup>\r
                <mml:msubsup><mml:mi>y</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msubsup>\r
            </mml:math></inlineequation>\r
        </para>\r
        <para>\r
            where <inlineequation><mml:math><mml:msubsup><mml:mi>x</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msubsup></mml:math></inlineequation> and\r
            <inlineequation><mml:math><mml:msubsup><mml:mi>y</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msubsup></mml:math></inlineequation> are\r
            the x and y window coordinates of the <emphasis>i</emphasis>th vertex of the n-vertex polygon.\r
        </para>\r
    </refsect1>\r
    <refsect1 id="versions"><title>Version Support</title>\r
        <informaltable frame="topbot">\r
            <tgroup cols="3" align="left">\r
                <colspec colwidth="1.1*" />\r
                <colspec colwidth="1*" align="center" />\r
                <colspec colwidth="1*" align="center" />\r
                <colspec colwidth="1*" align="center" />\r
                <colspec colwidth="1*" align="center" />\r
                <colspec colwidth="1*" align="center" />\r
                <colspec colwidth="1*" align="center" />\r
                <colspec colwidth="1*" align="center" />\r
                <colspec colwidth="1*" align="center" />\r
                <thead>\r
                    <row>\r
                        <entry rowsep="1" align="left"><emphasis role="bold">\r
                        Variable\r
                        </emphasis></entry>\r
                        <entry rowsep="1" align="left"><emphasis role="bold">\r
                        Version 1.10\r
                        </emphasis></entry>\r
                        <entry rowsep="1" align="left"><emphasis role="bold">\r
                        Version 1.20\r
                        </emphasis></entry>\r
                        <entry rowsep="1" align="left"><emphasis role="bold">\r
                        Version 1.30\r
                        </emphasis></entry>\r
                        <entry rowsep="1" align="left"><emphasis role="bold">\r
                        Version 1.40\r
                        </emphasis></entry>\r
                        <entry rowsep="1" align="left"><emphasis role="bold">\r
                        Version 1.50\r
                        </emphasis></entry>\r
                        <entry rowsep="1" align="left"><emphasis role="bold">\r
                        Version 3.30\r
                        </emphasis></entry>\r
                        <entry rowsep="1" align="left"><emphasis role="bold">\r
                        Version 4.00\r
                        </emphasis></entry>\r
                        <entry rowsep="1" align="left"><emphasis role="bold">\r
                        Version 4.10\r
                        </emphasis></entry>\r
                    </row>\r
                    <row>\r
                        <entry>\r
                            gl_FrontFacing\r
                        </entry>\r
                        <entry>\r
                            <emphasis>Y</emphasis>  <!-- 1.10, OpenGL 2.0 -->\r
                        </entry>\r
                        <entry>\r
                            <emphasis>Y</emphasis>  <!-- 1.20, OpenGL 2.1 -->\r
                        </entry>\r
                        <entry>\r
                            <emphasis>Y</emphasis>  <!-- 1.30, OpenGL 3.0 -->\r
                        </entry>\r
                        <entry>\r
                            <emphasis>Y</emphasis>  <!-- 1.40, OpenGL 3.1 -->\r
                        </entry>\r
                        <entry>\r
                            <emphasis>Y</emphasis>  <!-- 1.50, OpenGL 3.2 -->\r
                        </entry>\r
                        <entry>\r
                            <emphasis>Y</emphasis>  <!-- 3.30, OpenGL 3.3 -->\r
                        </entry>\r
                        <entry>\r
                            <emphasis>Y</emphasis>  <!-- 4.00, OpenGL 4.0 -->\r
                        </entry>\r
                        <entry>\r
                            <emphasis>Y</emphasis>  <!-- 4.10, OpenGL 4.1 -->\r
                        </entry>\r
                    </row>\r
                </thead>\r
            </tgroup>\r
        </informaltable>\r
    </refsect1>\r
    <refsect1 id="seealso"><title>See Also</title>\r
        <para>\r
            <citerefentry><refentrytitle>gl_FragCoord</refentrytitle></citerefentry>\r
        </para>\r
    </refsect1>\r
    <refsect1 id="Copyright"><title>Copyright</title>\r
        <para>\r
            Copyright <trademark class="copyright"></trademark> 2011 Khronos Group. \r
            This material may be distributed subject to the terms and conditions set forth in \r
            the Open Publication License, v 1.0, 8 June 1999.\r
            <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.\r
        </para>\r
    </refsect1>\r
</refentry>\r
Commit	Line	Data
7faf1d71 AW	1	<?xml version="1.0" encoding="UTF-8"?>\r
	2	<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"\r
	3	"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">\r
	4	<refentry id="gl_FrontFacing">\r
	5	<refmeta>\r
	6	<refmetainfo>\r
	7	<copyright>\r
	8	<year>2011</year>\r
	9	<holder>Khronos Group</holder>\r
	10	</copyright>\r
	11	</refmetainfo>\r
	12	<refentrytitle>gl_FrontFacing</refentrytitle>\r
	13	<manvolnum>3G</manvolnum>\r
	14	</refmeta>\r
	15	<refnamediv>\r
	16	<refname>gl_FrontFacing</refname>\r
	17	<refpurpose>indicates whether a primitive is front or back facing</refpurpose>\r
	18	</refnamediv>\r
	19	<refsynopsisdiv><title>Declaration</title>\r
	20	<funcsynopsis>\r
	21	<function>in bool gl_FrontFacing;</function>\r
	22	</funcsynopsis>\r
	23	</refsynopsisdiv>\r
	24	<refsect1 id="description"><title>Description</title>\r
	25	<para>\r
	26	Available only in the fragment language, <function>gl_FrontFacing</function> is an input variable\r
	27	whose value is <function>true</function> if the fragment belongs to a front-facing primitive and\r
	28	false otherwise. The determination of whether a triangle primitive is front-facing is made by\r
	29	examining the sign of the area of the triangle, including a possible reversal of this sign\r
	30	as controlled by <function>glFrontFace</function>. One way to compute this area is:\r
	31	</para>\r
	32	<para>\r
	33	<inlineequation><mml:math>\r
	34	<mml:mi>a</mml:mi><mml:mo>=</mml:mo><mml:mfrac><mml:mrow><mml:mn>1</mml:mn></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:mfrac>\r
	35	<mml:msubsup><mml:mo>∑</mml:mo><mml:mrow>\r
	36	<mml:mi>j</mml:mi><mml:mo>=</mml:mo><mml:mn>0</mml:mn>\r
	37	</mml:mrow>\r
	38	<mml:mrow>\r
	39	<mml:mi>n</mml:mi><mml:mo>-</mml:mo><mml:mn>1</mml:mn>\r
	40	</mml:mrow></mml:msubsup>\r
	41	<mml:msubsup><mml:mi>x</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msubsup>\r
	42	<mml:msubsup><mml:mi>y</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msubsup>\r
	43	<mml:mo>-</mml:mo>\r
	44	<mml:msubsup><mml:mi>x</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msubsup>\r
	45	<mml:msubsup><mml:mi>y</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msubsup>\r
	46	</mml:math></inlineequation>\r
	47	</para>\r
	48	<para>\r
	49	where <inlineequation><mml:math><mml:msubsup><mml:mi>x</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msubsup></mml:math></inlineequation> and\r
	50	<inlineequation><mml:math><mml:msubsup><mml:mi>y</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msubsup></mml:math></inlineequation> are\r
	51	the x and y window coordinates of the <emphasis>i</emphasis>th vertex of the n-vertex polygon.\r
	52	</para>\r
	53	</refsect1>\r
	54	<refsect1 id="versions"><title>Version Support</title>\r
	55	<informaltable frame="topbot">\r
	56	<tgroup cols="3" align="left">\r
	57	<colspec colwidth="1.1*" />\r
	58	<colspec colwidth="1*" align="center" />\r
	59	<colspec colwidth="1*" align="center" />\r
	60	<colspec colwidth="1*" align="center" />\r
	61	<colspec colwidth="1*" align="center" />\r
	62	<colspec colwidth="1*" align="center" />\r
	63	<colspec colwidth="1*" align="center" />\r
	64	<colspec colwidth="1*" align="center" />\r
65	<colspec colwidth="1*" align="center" />\r
66	<thead>\r
67	<row>\r
68	<entry rowsep="1" align="left"><emphasis role="bold">\r
69	Variable\r
70	</emphasis></entry>\r
71	<entry rowsep="1" align="left"><emphasis role="bold">\r
72	Version 1.10\r
73	</emphasis></entry>\r
74	<entry rowsep="1" align="left"><emphasis role="bold">\r
75	Version 1.20\r
76	</emphasis></entry>\r
77	<entry rowsep="1" align="left"><emphasis role="bold">\r
78	Version 1.30\r
79	</emphasis></entry>\r
80	<entry rowsep="1" align="left"><emphasis role="bold">\r
81	Version 1.40\r
82	</emphasis></entry>\r
83	<entry rowsep="1" align="left"><emphasis role="bold">\r
84	Version 1.50\r
85	</emphasis></entry>\r
86	<entry rowsep="1" align="left"><emphasis role="bold">\r
87	Version 3.30\r
88	</emphasis></entry>\r
89	<entry rowsep="1" align="left"><emphasis role="bold">\r
90	Version 4.00\r
91	</emphasis></entry>\r
92	<entry rowsep="1" align="left"><emphasis role="bold">\r
93	Version 4.10\r
94	</emphasis></entry>\r
95	</row>\r
96	<row>\r
97	<entry>\r
98	gl_FrontFacing\r
99	</entry>\r
100	<entry>\r
101	<emphasis>Y</emphasis> <!-- 1.10, OpenGL 2.0 -->\r
102	</entry>\r
103	<entry>\r
104	<emphasis>Y</emphasis> <!-- 1.20, OpenGL 2.1 -->\r
105	</entry>\r
106	<entry>\r
107	<emphasis>Y</emphasis> <!-- 1.30, OpenGL 3.0 -->\r
108	</entry>\r
109	<entry>\r
110	<emphasis>Y</emphasis> <!-- 1.40, OpenGL 3.1 -->\r
111	</entry>\r
112	<entry>\r
113	<emphasis>Y</emphasis> <!-- 1.50, OpenGL 3.2 -->\r
114	</entry>\r
115	<entry>\r
116	<emphasis>Y</emphasis> <!-- 3.30, OpenGL 3.3 -->\r
117	</entry>\r
118	<entry>\r
119	<emphasis>Y</emphasis> <!-- 4.00, OpenGL 4.0 -->\r
120	</entry>\r
121	<entry>\r
122	<emphasis>Y</emphasis> <!-- 4.10, OpenGL 4.1 -->\r
123	</entry>\r
124	</row>\r
125	</thead>\r
126	</tgroup>\r
127	</informaltable>\r
128	</refsect1>\r
129	<refsect1 id="seealso"><title>See Also</title>\r
130	<para>\r
131	<citerefentry><refentrytitle>gl_FragCoord</refentrytitle></citerefentry>\r
132	</para>\r
133	</refsect1>\r
134	<refsect1 id="Copyright"><title>Copyright</title>\r
135	<para>\r
136	Copyright <trademark class="copyright"></trademark> 2011 Khronos Group. \r
137	This material may be distributed subject to the terms and conditions set forth in \r
138	the Open Publication License, v 1.0, 8 June 1999.\r
139	<ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.\r
140	</para>\r
141	</refsect1>\r
142	</refentry>\r