192 lines
10 KiB
XML
192 lines
10 KiB
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="glMapBuffer">
|
|
<refmeta>
|
|
<refmetainfo>
|
|
<copyright>
|
|
<year>2005</year>
|
|
<holder>Sams Publishing</holder>
|
|
</copyright>
|
|
</refmetainfo>
|
|
<refentrytitle>glMapBuffer</refentrytitle>
|
|
<manvolnum>3G</manvolnum>
|
|
</refmeta>
|
|
<refnamediv>
|
|
<refname>glMapBuffer</refname>
|
|
<refpurpose>map a buffer object's data store</refpurpose>
|
|
</refnamediv>
|
|
<refsynopsisdiv><title>C Specification</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>void * <function>glMapBuffer</function></funcdef>
|
|
<paramdef>GLenum <parameter>target</parameter></paramdef>
|
|
<paramdef>GLenum <parameter>access</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
</refsynopsisdiv>
|
|
<refsect1 id="parameters"><title>Parameters</title>
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><parameter>target</parameter></term>
|
|
<listitem>
|
|
<para>
|
|
Specifies the target buffer object being mapped.
|
|
The symbolic constant must be
|
|
<constant>GL_ARRAY_BUFFER</constant>,
|
|
<constant>GL_COPY_READ_BUFFER</constant>,
|
|
<constant>GL_COPY_WRITE_BUFFER</constant>,
|
|
<constant>GL_ELEMENT_ARRAY_BUFFER</constant>,
|
|
<constant>GL_PIXEL_PACK_BUFFER</constant>,
|
|
<constant>GL_PIXEL_UNPACK_BUFFER</constant>,
|
|
<constant>GL_TEXTURE_BUFFER</constant>,
|
|
<constant>GL_TRANSFORM_FEEDBACK_BUFFER</constant> or
|
|
<constant>GL_UNIFORM_BUFFER</constant>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><parameter>access</parameter></term>
|
|
<listitem>
|
|
<para>
|
|
Specifies the access policy, indicating whether it will be possible to read from, write to,
|
|
or both read from and write to the buffer object's mapped data store. The symbolic constant must be
|
|
<constant>GL_READ_ONLY</constant>, <constant>GL_WRITE_ONLY</constant>, or <constant>GL_READ_WRITE</constant>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
<refsynopsisdiv><title>C Specification</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>GLboolean <function>glUnmapBuffer</function></funcdef>
|
|
<paramdef>GLenum <parameter>target</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
</refsynopsisdiv>
|
|
<!-- eqn: ignoring delim $$ -->
|
|
<refsect1 id="parameters2"><title>Parameters</title>
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><parameter>target</parameter></term>
|
|
<listitem>
|
|
<para>
|
|
Specifies the target buffer object being unmapped.
|
|
The symbolic constant must be
|
|
<constant>GL_ARRAY_BUFFER</constant>,
|
|
<constant>GL_COPY_READ_BUFFER</constant>,
|
|
<constant>GL_COPY_WRITE_BUFFER</constant>,
|
|
<constant>GL_ELEMENT_ARRAY_BUFFER</constant>,
|
|
<constant>GL_PIXEL_PACK_BUFFER</constant>,
|
|
<constant>GL_PIXEL_UNPACK_BUFFER</constant>,
|
|
<constant>GL_TEXTURE_BUFFER</constant>,
|
|
<constant>GL_TRANSFORM_FEEDBACK_BUFFER</constant> or
|
|
<constant>GL_UNIFORM_BUFFER</constant>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
<refsect1 id="description"><title>Description</title>
|
|
<para>
|
|
<function>glMapBuffer</function> maps to the client's address space the entire data store of the buffer object
|
|
currently bound to <parameter>target</parameter>. The data can then be directly read and/or written relative to
|
|
the returned pointer, depending on the specified <parameter>access</parameter> policy. If the GL is unable to
|
|
map the buffer object's data store, <function>glMapBuffer</function> generates an error and returns
|
|
<constant>NULL</constant>. This may occur for system-specific reasons, such as low virtual memory availability.
|
|
</para>
|
|
<para>
|
|
If a mapped data store is accessed in a way inconsistent with the specified <parameter>access</parameter> policy,
|
|
no error is generated, but performance may be negatively impacted and system errors, including program
|
|
termination, may result. Unlike the <parameter>usage</parameter> parameter of <function>glBufferData</function>,
|
|
<parameter>access</parameter> is not a hint, and does in fact constrain the usage of the mapped data store on
|
|
some GL implementations. In order to achieve the highest performance available, a buffer object's data store
|
|
should be used in ways consistent with both its specified <parameter>usage</parameter> and
|
|
<parameter>access</parameter> parameters.
|
|
</para>
|
|
<para>
|
|
A mapped data store must be unmapped with <function>glUnmapBuffer</function> before its buffer object is used.
|
|
Otherwise an error will be generated by any GL command that attempts to dereference the buffer object's data store.
|
|
When a data store is unmapped, the pointer to its data store becomes invalid. <function>glUnmapBuffer</function>
|
|
returns <constant>GL_TRUE</constant> unless the data store contents have become corrupt during the time
|
|
the data store was mapped. This can occur for system-specific reasons that affect the availability of graphics
|
|
memory, such as screen mode changes. In such situations, <constant>GL_FALSE</constant> is returned and the
|
|
data store contents are undefined. An application must detect this rare condition and reinitialize the data store.
|
|
</para>
|
|
<para>
|
|
A buffer object's mapped data store is automatically unmapped when the buffer object is deleted or its data store
|
|
is recreated with <function>glBufferData</function>.
|
|
</para>
|
|
</refsect1>
|
|
<refsect1 id="notes"><title>Notes</title>
|
|
<para>
|
|
If an error is generated, <function>glMapBuffer</function> returns <constant>NULL</constant>, and
|
|
<function>glUnmapBuffer</function> returns <constant>GL_FALSE</constant>.
|
|
</para>
|
|
<para>
|
|
Parameter values passed to GL commands may not be sourced from the returned pointer. No error will be generated,
|
|
but results will be undefined and will likely vary across GL implementations.
|
|
</para>
|
|
</refsect1>
|
|
<refsect1 id="errors"><title>Errors</title>
|
|
<para>
|
|
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not
|
|
<constant>GL_ARRAY_BUFFER</constant>,
|
|
<constant>GL_COPY_READ_BUFFER</constant>,
|
|
<constant>GL_COPY_WRITE_BUFFER</constant>,
|
|
<constant>GL_ELEMENT_ARRAY_BUFFER</constant>,
|
|
<constant>GL_PIXEL_PACK_BUFFER</constant>,
|
|
<constant>GL_PIXEL_UNPACK_BUFFER</constant>,
|
|
<constant>GL_TEXTURE_BUFFER</constant>,
|
|
<constant>GL_TRANSFORM_FEEDBACK_BUFFER</constant> or
|
|
<constant>GL_UNIFORM_BUFFER</constant>.
|
|
</para>
|
|
<para>
|
|
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>access</parameter> is not
|
|
<constant>GL_READ_ONLY</constant>, <constant>GL_WRITE_ONLY</constant>, or <constant>GL_READ_WRITE</constant>.
|
|
</para>
|
|
<para>
|
|
<constant>GL_OUT_OF_MEMORY</constant> is generated when <function>glMapBuffer</function> is executed
|
|
if the GL is unable to map the buffer object's data store. This may occur for a variety of system-specific
|
|
reasons, such as the absence of sufficient remaining virtual memory.
|
|
</para>
|
|
<para>
|
|
<constant>GL_INVALID_OPERATION</constant> is generated if the reserved buffer object name 0 is bound to <parameter>target</parameter>.
|
|
</para>
|
|
<para>
|
|
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glMapBuffer</function> is executed for
|
|
a buffer object whose data store is already mapped.
|
|
</para>
|
|
<para>
|
|
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glUnmapBuffer</function> is executed for
|
|
a buffer object whose data store is not currently mapped.
|
|
</para>
|
|
</refsect1>
|
|
<refsect1 id="associatedgets"><title>Associated Gets</title>
|
|
<para>
|
|
<citerefentry><refentrytitle>glGetBufferPointerv</refentrytitle></citerefentry> with argument <constant>GL_BUFFER_MAP_POINTER</constant>
|
|
</para>
|
|
<para>
|
|
<citerefentry><refentrytitle>glGetBufferParameter</refentrytitle></citerefentry> with argument <constant>GL_BUFFER_MAPPED</constant>, <constant>GL_BUFFER_ACCESS</constant>, or <constant>GL_BUFFER_USAGE</constant>
|
|
</para>
|
|
</refsect1>
|
|
<refsect1 id="seealso"><title>See Also</title>
|
|
<para>
|
|
<citerefentry><refentrytitle>glBindBuffer</refentrytitle></citerefentry>,
|
|
<citerefentry><refentrytitle>glBindBufferBase</refentrytitle></citerefentry>,
|
|
<citerefentry><refentrytitle>glBindBufferRange</refentrytitle></citerefentry>,
|
|
<citerefentry><refentrytitle>glBufferData</refentrytitle></citerefentry>,
|
|
<citerefentry><refentrytitle>glBufferSubData</refentrytitle></citerefentry>,
|
|
<citerefentry><refentrytitle>glDeleteBuffers</refentrytitle></citerefentry>
|
|
</para>
|
|
</refsect1>
|
|
<refsect1 id="Copyright"><title>Copyright</title>
|
|
<para>
|
|
Copyright <trademark class="copyright"></trademark> 2005 Addison-Wesley.
|
|
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>
|