[clinton/guile-figl.git] / upstream-doc / man2 / glClear.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="glClear">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>1991-2006</year>
                <holder>Silicon Graphics, Inc.</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>glClear</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glClear</refname>
        <refpurpose>clear buffers to preset values</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glClear</function></funcdef>
                <paramdef>GLbitfield <parameter>mask</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>mask</parameter></term>
            <listitem>
                <para>
                    Bitwise OR of masks that indicate the buffers to be cleared.
                    The four masks are
                    <constant>GL_COLOR_BUFFER_BIT</constant>,
                    <constant>GL_DEPTH_BUFFER_BIT</constant>,
                    <constant>GL_ACCUM_BUFFER_BIT</constant>, and
                    <constant>GL_STENCIL_BUFFER_BIT</constant>.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>glClear</function> sets the bitplane area of the window to values previously selected
            by <function>glClearColor</function>, <function>glClearIndex</function>, <function>glClearDepth</function>,
            <function>glClearStencil</function>, and <function>glClearAccum</function>.
            Multiple color buffers can be cleared simultaneously by selecting
            more than one buffer at a time using <citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>.
        </para>
        <para>
            The pixel ownership test,
            the scissor test,
            dithering, and the buffer writemasks affect the operation of <function>glClear</function>.
            The scissor box bounds the cleared region.
            Alpha function,
            blend function,
            logical operation,
            stenciling,
            texture mapping,
            and depth-buffering are ignored by <function>glClear</function>.
        </para>
        <para>
            <function>glClear</function> takes a single argument that is the bitwise OR of several
            values indicating which buffer is to be cleared.
        </para>
        <para>
            The values are as follows:
        </para>
        <variablelist>
            <varlistentry>
                <term><constant>GL_COLOR_BUFFER_BIT</constant></term>
                <listitem>
                    <para>
                        Indicates the buffers currently enabled for color
                        writing.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_DEPTH_BUFFER_BIT</constant></term>
                <listitem>
                    <para>
                        Indicates the depth buffer.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_ACCUM_BUFFER_BIT</constant></term>
                <listitem>
                    <para>
                        Indicates the accumulation buffer.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_STENCIL_BUFFER_BIT</constant></term>
                <listitem>
                    <para>
                        Indicates the stencil buffer.
                    </para>
                </listitem>
            </varlistentry>
        </variablelist>
        <para>
            The value to which each buffer is cleared depends on the setting of the
            clear value for that buffer.
        </para>
    </refsect1>
    <refsect1 id="notes"><title>Notes</title>
        <para>
            If a buffer is not present,
            then a <function>glClear</function> directed at that buffer has no effect.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_VALUE</constant> is generated if any bit other than the four defined
            bits is set in <parameter>mask</parameter>.
        </para>
        <para>
            <constant>GL_INVALID_OPERATION</constant> is generated if <function>glClear</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="associatedgets"><title>Associated Gets</title>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_ACCUM_CLEAR_VALUE</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_DEPTH_CLEAR_VALUE</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_INDEX_CLEAR_VALUE</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_COLOR_CLEAR_VALUE</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_STENCIL_CLEAR_VALUE</constant>
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <function>glClearAccum</function>,
            <function>glClearColor</function>,
            <function>glClearDepth</function>,
            <function>glClearIndex</function>,
            <function>glClearStencil</function>,
            <citerefentry><refentrytitle>glColorMask</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glDepthMask</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glScissor</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glStencilMask</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="glClear">
	5	<refmeta>
	6	<refmetainfo>
	7	<copyright>
	8	<year>1991-2006</year>
	9	<holder>Silicon Graphics, Inc.</holder>
	10	</copyright>
	11	</refmetainfo>
	12	<refentrytitle>glClear</refentrytitle>
	13	<manvolnum>3G</manvolnum>
	14	</refmeta>
	15	<refnamediv>
	16	<refname>glClear</refname>
	17	<refpurpose>clear buffers to preset values</refpurpose>
	18	</refnamediv>
	19	<refsynopsisdiv><title>C Specification</title>
	20	<funcsynopsis>
	21	<funcprototype>
	22	<funcdef>void <function>glClear</function></funcdef>
	23	<paramdef>GLbitfield <parameter>mask</parameter></paramdef>
	24	</funcprototype>
	25	</funcsynopsis>
	26	</refsynopsisdiv>
	27	<refsect1 id="parameters"><title>Parameters</title>
	28	<variablelist>
	29	<varlistentry>
	30	<term><parameter>mask</parameter></term>
	31	<listitem>
	32	<para>
	33	Bitwise OR of masks that indicate the buffers to be cleared.
	34	The four masks are
	35	<constant>GL_COLOR_BUFFER_BIT</constant>,
	36	<constant>GL_DEPTH_BUFFER_BIT</constant>,
	37	<constant>GL_ACCUM_BUFFER_BIT</constant>, and
	38	<constant>GL_STENCIL_BUFFER_BIT</constant>.
	39	</para>
	40	</listitem>
	41	</varlistentry>
	42	</variablelist>
	43	</refsect1>
	44	<refsect1 id="description"><title>Description</title>
	45	<para>
	46	<function>glClear</function> sets the bitplane area of the window to values previously selected
	47	by <function>glClearColor</function>, <function>glClearIndex</function>, <function>glClearDepth</function>,
	48	<function>glClearStencil</function>, and <function>glClearAccum</function>.
	49	Multiple color buffers can be cleared simultaneously by selecting
	50	more than one buffer at a time using <citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>.
	51	</para>
	52	<para>
	53	The pixel ownership test,
	54	the scissor test,
	55	dithering, and the buffer writemasks affect the operation of <function>glClear</function>.
	56	The scissor box bounds the cleared region.
	57	Alpha function,
	58	blend function,
	59	logical operation,
	60	stenciling,
	61	texture mapping,
	62	and depth-buffering are ignored by <function>glClear</function>.
	63	</para>
	64	<para>
65	<function>glClear</function> takes a single argument that is the bitwise OR of several
66	values indicating which buffer is to be cleared.
67	</para>
68	<para>
69	The values are as follows:
70	</para>
71	<variablelist>
72	<varlistentry>
73	<term><constant>GL_COLOR_BUFFER_BIT</constant></term>
74	<listitem>
75	<para>
76	Indicates the buffers currently enabled for color
77	writing.
78	</para>
79	</listitem>
80	</varlistentry>
81	<varlistentry>
82	<term><constant>GL_DEPTH_BUFFER_BIT</constant></term>
83	<listitem>
84	<para>
85	Indicates the depth buffer.
86	</para>
87	</listitem>
88	</varlistentry>
89	<varlistentry>
90	<term><constant>GL_ACCUM_BUFFER_BIT</constant></term>
91	<listitem>
92	<para>
93	Indicates the accumulation buffer.
94	</para>
95	</listitem>
96	</varlistentry>
97	<varlistentry>
98	<term><constant>GL_STENCIL_BUFFER_BIT</constant></term>
99	<listitem>
100	<para>
101	Indicates the stencil buffer.
102	</para>
103	</listitem>
104	</varlistentry>
105	</variablelist>
106	<para>
107	The value to which each buffer is cleared depends on the setting of the
108	clear value for that buffer.
109	</para>
110	</refsect1>
111	<refsect1 id="notes"><title>Notes</title>
112	<para>
113	If a buffer is not present,
114	then a <function>glClear</function> directed at that buffer has no effect.
115	</para>
116	</refsect1>
117	<refsect1 id="errors"><title>Errors</title>
118	<para>
119	<constant>GL_INVALID_VALUE</constant> is generated if any bit other than the four defined
120	bits is set in <parameter>mask</parameter>.
121	</para>
122	<para>
123	<constant>GL_INVALID_OPERATION</constant> is generated if <function>glClear</function>
124	is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
125	and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
126	</para>
127	</refsect1>
128	<refsect1 id="associatedgets"><title>Associated Gets</title>
129	<para>
130	<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_ACCUM_CLEAR_VALUE</constant>
131	</para>
132	<para>
133	<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_DEPTH_CLEAR_VALUE</constant>
134	</para>
135	<para>
136	<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_INDEX_CLEAR_VALUE</constant>
137	</para>
138	<para>
139	<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_COLOR_CLEAR_VALUE</constant>
140	</para>
141	<para>
142	<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_STENCIL_CLEAR_VALUE</constant>
143	</para>
144	</refsect1>
145	<refsect1 id="seealso"><title>See Also</title>
146	<para>
147	<function>glClearAccum</function>,
148	<function>glClearColor</function>,
149	<function>glClearDepth</function>,
150	<function>glClearIndex</function>,
151	<function>glClearStencil</function>,
152	<citerefentry><refentrytitle>glColorMask</refentrytitle></citerefentry>,
153	<citerefentry><refentrytitle>glDepthMask</refentrytitle></citerefentry>,
154	<citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>,
155	<citerefentry><refentrytitle>glScissor</refentrytitle></citerefentry>,
156	<citerefentry><refentrytitle>glStencilMask</refentrytitle></citerefentry>
157	</para>
158	</refsect1>
159	<refsect1 id="Copyright"><title>Copyright</title>
160	<para>
161	Copyright <trademark class="copyright"></trademark> 1991-2006
162	Silicon Graphics, Inc. This document is licensed under the SGI
163	Free Software B License. For details, see
164	<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
165	</para>
166	</refsect1>
167	</refentry>