[clinton/guile-figl.git] / upstream-doc / manglsl / gl_Layer.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_Layer">\r
    <refmeta>\r
        <refmetainfo>\r
            <copyright>\r
                <year>2012</year>\r
                <holder>Khronos Group</holder>\r
            </copyright>\r
        </refmetainfo>\r
        <refentrytitle>gl_Layer</refentrytitle>\r
        <manvolnum>3G</manvolnum>\r
    </refmeta>\r
    <refnamediv>\r
        <refname>gl_Layer</refname>\r
        <refpurpose>contains the selected layer of a multi-layer framebuffer attachment</refpurpose>\r
    </refnamediv>\r
    <refsynopsisdiv><title>Declaration</title>\r
        <funcsynopsis>\r
            <function>out int gl_Layer; // Geometry stage</function>\r
        </funcsynopsis>\r
        <funcsynopsis>\r
            <function>in int gl_Layer; // Fragment stage</function>\r
        </funcsynopsis>\r
    </refsynopsisdiv>\r
    <refsect1 id="description"><title>Description</title>\r
        <para>\r
            In the geometry language, <function>gl_Layer</function> is used to select a specific\r
            layer (or face and layer of cube map) in a multi-layer framebuffer attachment. The actual\r
            layer used will come from one of the vertices in the primitive being shaded. Which vertex\r
            the layer comes from is undefined and as such it is recommended to write the same value\r
            to <function>gl_Layer</function> for all vertices in the primitive. If a shader statically\r
            assigns a value to <function>gl_Layer</function>, layered rendering mode is enabled.\r
            If a shader statically assigns a value to <function>gl_Layer</function>, and there is an execution path through\r
            the shader that does not set <function>gl_Layer</function>, then the value of <function>gl_Layer</function>\r
            is undefined for invocations of the shader that take that path.\r
        </para>\r
        <para>\r
            When used with an array of cube map textures, the <function>gl_Layer</function> output variable\r
            takes on a special value. Instead of referring to only the layer, it is used to select a cube map\r
            face and a layer. Setting <function>gl_Layer</function> to the value\r
            <inlineequation><mml:math><mml:mi>layer</mml:mi><mml:mo>*</mml:mo><mml:mn>6</mml:mn><mml:mo>+</mml:mo><mml:mi>face</mml:mi></mml:math></inlineequation>\r
            will render to <inlineequation><mml:math><mml:mi>face</mml:mi></mml:math></inlineequation>\r
            of the cube defined in <inlineequation><mml:math><mml:mi>layer</mml:mi></mml:math></inlineequation>.\r
            The face values are as follows:\r
        <informaltable frame="topbot">\r
            <tgroup cols="2" align="left">\r
                <colspec colwidth="1.1*" />\r
                <colspec colwidth="1*" align="center" />\r
                <thead>\r
                    <row>\r
                        <entry rowsep="1" align="left"><emphasis role="bold">\r
                        Face Value\r
                        </emphasis></entry>\r
                        <entry rowsep="1" align="left"><emphasis role="bold">\r
                        Resulting Target\r
                        </emphasis></entry>\r
                    </row>\r
                    <row>\r
                        <entry>\r
                            0\r
                        </entry>\r
                        <entry>\r
                            <constant>GL_TEXTURE_CUBEMAP_POSITIVE_X</constant>\r
                        </entry>\r
                    </row>\r
                    <row>\r
                        <entry>\r
                            1\r
                        </entry>\r
                        <entry>\r
                            <constant>GL_TEXTURE_CUBEMAP_NEGATIVE_X</constant>\r
                        </entry>\r
                    </row>\r
                    <row>\r
                        <entry>\r
                            2\r
                        </entry>\r
                        <entry>\r
                            <constant>GL_TEXTURE_CUBEMAP_POSITIVE_Y</constant>\r
                        </entry>\r
                    </row>\r
                    <row>\r
                        <entry>\r
                            3\r
                        </entry>\r
                        <entry>\r
                            <constant>GL_TEXTURE_CUBEMAP_NEGATIVE_Y</constant>\r
                        </entry>\r
                    </row>\r
                    <row>\r
                        <entry>\r
                            4\r
                        </entry>\r
                        <entry>\r
                            <constant>GL_TEXTURE_CUBEMAP_POSITIVE_Z</constant>\r
                        </entry>\r
                    </row>\r
                    <row>\r
                        <entry>\r
                            5\r
                        </entry>\r
                        <entry>\r
                            <constant>GL_TEXTURE_CUBEMAP_NEGATIVE_Z</constant>\r
                        </entry>\r
                    </row>\r
                </thead>\r
            </tgroup>\r
        </informaltable>\r
        </para>\r
        <para>\r
            For example, to render to the positive y cube map face located in the 5<superscript>th</superscript> layer of the\r
            cube map array, <function>gl_Layer</function> should be set to\r
            <inlineequation><mml:math><mml:mn>5</mml:mn><mml:mo>*</mml:mo><mml:mn>6</mml:mn><mml:mo>+</mml:mo><mml:mn>2</mml:mn></mml:math></inlineequation>.\r
        </para>\r
        <para>\r
            The input variable <function>gl_Layer</function> in the fragment language will have the same value that was written to the\r
            output variable <function>gl_Layer</function> in the geometry language. If the geometry stage does not dynamically assign a\r
            value to <function>gl_Layer</function>, the value of <function>gl_Layer</function> in the fragment stage will be undefined.  If the geometry stage\r
            makes no static assignment to <function>gl_Layer</function>, the input <function>gl_Layer</function> in the fragment stage will be zero.  Otherwise,\r
            the fragment stage will read the same value written by the geometry stage, even if that value is out of\r
            range.  If a fragment shader contains a static access to <function>gl_Layer</function>, it will count against the implementation\r
            defined limit for the maximum number of inputs to the fragment stage.\r
        </para>\r
    </refsect1>\r
    <refsect1 id="versions"><title>Version Support</title>\r
        <informaltable frame="topbot">\r
            #VARTABLECOLS#\r
                <thead>\r
                    #FUNCTABLEHEADER#\r
                    <row>\r
                        <entry>gl_Layer (geometry stage)</entry>#newin15#\r
                    </row>\r
                    <row>\r
                        <entry>gl_Layer (fragment stage)</entry>#newin43#\r
                    </row>\r
                </thead>\r
            </tgroup>\r
        </informaltable>\r
    </refsect1>\r
    <refsect1 id="seealso"><title>See Also</title>\r
        <para>\r
            <citerefentry><refentrytitle>gl_ViewportIndex</refentrytitle></citerefentry>\r
        </para>\r
    </refsect1>\r
    <refsect1 id="Copyright"><title>Copyright</title>\r
        <para>\r
            Copyright <trademark class="copyright"></trademark> 2011-2012 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_Layer">\r
	5	<refmeta>\r
	6	<refmetainfo>\r
	7	<copyright>\r
	8	<year>2012</year>\r
	9	<holder>Khronos Group</holder>\r
	10	</copyright>\r
	11	</refmetainfo>\r
	12	<refentrytitle>gl_Layer</refentrytitle>\r
	13	<manvolnum>3G</manvolnum>\r
	14	</refmeta>\r
	15	<refnamediv>\r
	16	<refname>gl_Layer</refname>\r
	17	<refpurpose>contains the selected layer of a multi-layer framebuffer attachment</refpurpose>\r
	18	</refnamediv>\r
	19	<refsynopsisdiv><title>Declaration</title>\r
	20	<funcsynopsis>\r
	21	<function>out int gl_Layer; // Geometry stage</function>\r
	22	</funcsynopsis>\r
	23	<funcsynopsis>\r
	24	<function>in int gl_Layer; // Fragment stage</function>\r
	25	</funcsynopsis>\r
	26	</refsynopsisdiv>\r
	27	<refsect1 id="description"><title>Description</title>\r
	28	<para>\r
	29	In the geometry language, <function>gl_Layer</function> is used to select a specific\r
	30	layer (or face and layer of cube map) in a multi-layer framebuffer attachment. The actual\r
	31	layer used will come from one of the vertices in the primitive being shaded. Which vertex\r
	32	the layer comes from is undefined and as such it is recommended to write the same value\r
	33	to <function>gl_Layer</function> for all vertices in the primitive. If a shader statically\r
	34	assigns a value to <function>gl_Layer</function>, layered rendering mode is enabled.\r
	35	If a shader statically assigns a value to <function>gl_Layer</function>, and there is an execution path through\r
	36	the shader that does not set <function>gl_Layer</function>, then the value of <function>gl_Layer</function>\r
	37	is undefined for invocations of the shader that take that path.\r
	38	</para>\r
	39	<para>\r
	40	When used with an array of cube map textures, the <function>gl_Layer</function> output variable\r
	41	takes on a special value. Instead of referring to only the layer, it is used to select a cube map\r
	42	face and a layer. Setting <function>gl_Layer</function> to the value\r
	43	<inlineequation><mml:math><mml:mi>layer</mml:mi><mml:mo>*</mml:mo><mml:mn>6</mml:mn><mml:mo>+</mml:mo><mml:mi>face</mml:mi></mml:math></inlineequation>\r
	44	will render to <inlineequation><mml:math><mml:mi>face</mml:mi></mml:math></inlineequation>\r
	45	of the cube defined in <inlineequation><mml:math><mml:mi>layer</mml:mi></mml:math></inlineequation>.\r
	46	The face values are as follows:\r
	47	<informaltable frame="topbot">\r
	48	<tgroup cols="2" align="left">\r
	49	<colspec colwidth="1.1*" />\r
	50	<colspec colwidth="1*" align="center" />\r
	51	<thead>\r
	52	<row>\r
	53	<entry rowsep="1" align="left"><emphasis role="bold">\r
	54	Face Value\r
	55	</emphasis></entry>\r
	56	<entry rowsep="1" align="left"><emphasis role="bold">\r
	57	Resulting Target\r
	58	</emphasis></entry>\r
	59	</row>\r
	60	<row>\r
	61	<entry>\r
	62	0\r
	63	</entry>\r
	64	<entry>\r
65	<constant>GL_TEXTURE_CUBEMAP_POSITIVE_X</constant>\r
66	</entry>\r
67	</row>\r
68	<row>\r
69	<entry>\r
70	1\r
71	</entry>\r
72	<entry>\r
73	<constant>GL_TEXTURE_CUBEMAP_NEGATIVE_X</constant>\r
74	</entry>\r
75	</row>\r
76	<row>\r
77	<entry>\r
78	2\r
79	</entry>\r
80	<entry>\r
81	<constant>GL_TEXTURE_CUBEMAP_POSITIVE_Y</constant>\r
82	</entry>\r
83	</row>\r
84	<row>\r
85	<entry>\r
86	3\r
87	</entry>\r
88	<entry>\r
89	<constant>GL_TEXTURE_CUBEMAP_NEGATIVE_Y</constant>\r
90	</entry>\r
91	</row>\r
92	<row>\r
93	<entry>\r
94	4\r
95	</entry>\r
96	<entry>\r
97	<constant>GL_TEXTURE_CUBEMAP_POSITIVE_Z</constant>\r
98	</entry>\r
99	</row>\r
100	<row>\r
101	<entry>\r
102	5\r
103	</entry>\r
104	<entry>\r
105	<constant>GL_TEXTURE_CUBEMAP_NEGATIVE_Z</constant>\r
106	</entry>\r
107	</row>\r
108	</thead>\r
109	</tgroup>\r
110	</informaltable>\r
111	</para>\r
112	<para>\r
113	For example, to render to the positive y cube map face located in the 5<superscript>th</superscript> layer of the\r
114	cube map array, <function>gl_Layer</function> should be set to\r
115	<inlineequation><mml:math><mml:mn>5</mml:mn><mml:mo>*</mml:mo><mml:mn>6</mml:mn><mml:mo>+</mml:mo><mml:mn>2</mml:mn></mml:math></inlineequation>.\r
116	</para>\r
117	<para>\r
118	The input variable <function>gl_Layer</function> in the fragment language will have the same value that was written to the\r
119	output variable <function>gl_Layer</function> in the geometry language. If the geometry stage does not dynamically assign a\r
120	value to <function>gl_Layer</function>, the value of <function>gl_Layer</function> in the fragment stage will be undefined. If the geometry stage\r
121	makes no static assignment to <function>gl_Layer</function>, the input <function>gl_Layer</function> in the fragment stage will be zero. Otherwise,\r
122	the fragment stage will read the same value written by the geometry stage, even if that value is out of\r
123	range. If a fragment shader contains a static access to <function>gl_Layer</function>, it will count against the implementation\r
124	defined limit for the maximum number of inputs to the fragment stage.\r
125	</para>\r
126	</refsect1>\r
127	<refsect1 id="versions"><title>Version Support</title>\r
128	<informaltable frame="topbot">\r
129	#VARTABLECOLS#\r
130	<thead>\r
131	#FUNCTABLEHEADER#\r
132	<row>\r
133	<entry>gl_Layer (geometry stage)</entry>#newin15#\r
134	</row>\r
135	<row>\r
136	<entry>gl_Layer (fragment stage)</entry>#newin43#\r
137	</row>\r
138	</thead>\r
139	</tgroup>\r
140	</informaltable>\r
141	</refsect1>\r
142	<refsect1 id="seealso"><title>See Also</title>\r
143	<para>\r
144	<citerefentry><refentrytitle>gl_ViewportIndex</refentrytitle></citerefentry>\r
145	</para>\r
146	</refsect1>\r
147	<refsect1 id="Copyright"><title>Copyright</title>\r
148	<para>\r
149	Copyright <trademark class="copyright"></trademark> 2011-2012 Khronos Group. \r
150	This material may be distributed subject to the terms and conditions set forth in \r
151	the Open Publication License, v 1.0, 8 June 1999.\r
152	<ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.\r
153	</para>\r
154	</refsect1>\r
155	</refentry>\r