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NAME
glMapBufferRange, glMapNamedBufferRange - map all or part of a buffer object's data store
into the client's address space
C SPECIFICATION
void *glMapBufferRange(GLenum target, GLintptr offset, GLsizeiptr length,
GLbitfield access);
void *glMapNamedBufferRange(GLuint buffer, GLintptr offset, GLsizei length,
GLbitfield access);
PARAMETERS
target
Specifies the target to which the buffer object is bound for glMapBufferRange, which
must be one of the buffer binding targets in the following table:
┌─────────────────────────────┬────────────────────────────────┐
│Buffer Binding Target │ Purpose │
├─────────────────────────────┼────────────────────────────────┤
│GL_ARRAY_BUFFER │ Vertex attributes │
├─────────────────────────────┼────────────────────────────────┤
│GL_ATOMIC_COUNTER_BUFFER │ Atomic counter storage │
├─────────────────────────────┼────────────────────────────────┤
│GL_COPY_READ_BUFFER │ Buffer copy source │
├─────────────────────────────┼────────────────────────────────┤
│GL_COPY_WRITE_BUFFER │ Buffer copy destination │
├─────────────────────────────┼────────────────────────────────┤
│GL_DISPATCH_INDIRECT_BUFFER │ Indirect compute dispatch │
│ │ commands │
├─────────────────────────────┼────────────────────────────────┤
│GL_DRAW_INDIRECT_BUFFER │ Indirect command arguments │
├─────────────────────────────┼────────────────────────────────┤
│GL_ELEMENT_ARRAY_BUFFER │ Vertex array indices │
├─────────────────────────────┼────────────────────────────────┤
│GL_PIXEL_PACK_BUFFER │ Pixel read target │
├─────────────────────────────┼────────────────────────────────┤
│GL_PIXEL_UNPACK_BUFFER │ Texture data source │
├─────────────────────────────┼────────────────────────────────┤
│GL_QUERY_BUFFER │ Query result buffer │
├─────────────────────────────┼────────────────────────────────┤
│GL_SHADER_STORAGE_BUFFER │ Read-write storage for shaders │
├─────────────────────────────┼────────────────────────────────┤
│GL_TEXTURE_BUFFER │ Texture data buffer │
├─────────────────────────────┼────────────────────────────────┤
│GL_TRANSFORM_FEEDBACK_BUFFER │ Transform feedback buffer │
├─────────────────────────────┼────────────────────────────────┤
│GL_UNIFORM_BUFFER │ Uniform block storage │
└─────────────────────────────┴────────────────────────────────┘
buffer
Specifies the name of the buffer object for glMapNamedBufferRange.
offset
Specifies the starting offset within the buffer of the range to be mapped.
length
Specifies the length of the range to be mapped.
access
Specifies a combination of access flags indicating the desired access to the mapped
range.
DESCRIPTION
glMapBufferRange and glMapNamedBufferRange map all or part of the data store of a
specified buffer object into the client's address space. offset and length indicate the
range of data in the buffer object that is to be mapped, in terms of basic machine units.
access is a bitfield containing flags which describe the requested mapping. These flags
are described below.
A pointer to the beginning of the mapped range is returned once all pending operations on
the buffer object have completed, and may be used to modify and/or query the corresponding
range of the data store according to the following flag bits set in access:
• GL_MAP_READ_BIT indicates that the returned pointer may be used to read buffer object
data. No GL error is generated if the pointer is used to query a mapping which
excludes this flag, but the result is undefined and system errors (possibly including
program termination) may occur.
• GL_MAP_WRITE_BIT indicates that the returned pointer may be used to modify buffer
object data. No GL error is generated if the pointer is used to modify a mapping which
excludes this flag, but the result is undefined and system errors (possibly including
program termination) may occur.
• GL_MAP_PERSISTENT_BIT indicates that the mapping is to be made in a persistent fassion
and that the client intends to hold and use the returned pointer during subsequent GL
operation. It is not an error to call drawing commands (render) while buffers are
mapped using this flag. It is an error to specify this flag if the buffer's data store
was not allocated through a call to the glBufferStorage() command in which the
GL_MAP_PERSISTENT_BIT was also set.
• GL_MAP_COHERENT_BIT indicates that a persistent mapping is also to be coherent.
Coherent maps guarantee that the effect of writes to a buffer's data store by either
the client or server will eventually become visible to the other without further
intervention from the application. In the absence of this bit, persistent mappings are
not coherent and modified ranges of the buffer store must be explicitly communicated
to the GL, either by unmapping the buffer, or through a call to
glFlushMappedBufferRange() or glMemoryBarrier().
The following optional flag bits in access may be used to modify the mapping:
• GL_MAP_INVALIDATE_RANGE_BIT indicates that the previous contents of the specified
range may be discarded. Data within this range are undefined with the exception of
subsequently written data. No GL error is generated if subsequent GL operations access
unwritten data, but the result is undefined and system errors (possibly including
program termination) may occur. This flag may not be used in combination with
GL_MAP_READ_BIT.
• GL_MAP_INVALIDATE_BUFFER_BIT indicates that the previous contents of the entire buffer
may be discarded. Data within the entire buffer are undefined with the exception of
subsequently written data. No GL error is generated if subsequent GL operations access
unwritten data, but the result is undefined and system errors (possibly including
program termination) may occur. This flag may not be used in combination with
GL_MAP_READ_BIT.
• GL_MAP_FLUSH_EXPLICIT_BIT indicates that one or more discrete subranges of the mapping
may be modified. When this flag is set, modifications to each subrange must be
explicitly flushed by calling glFlushMappedBufferRange(). No GL error is set if a
subrange of the mapping is modified and not flushed, but data within the corresponding
subrange of the buffer are undefined. This flag may only be used in conjunction with
GL_MAP_WRITE_BIT. When this option is selected, flushing is strictly limited to
regions that are explicitly indicated with calls to glFlushMappedBufferRange() prior
to unmap; if this option is not selected glUnmapBuffer() will automatically flush the
entire mapped range when called.
• GL_MAP_UNSYNCHRONIZED_BIT indicates that the GL should not attempt to synchronize
pending operations on the buffer prior to returning from glMapBufferRange or
glMapNamedBufferRange. No GL error is generated if pending operations which source or
modify the buffer overlap the mapped region, but the result of such previous and any
subsequent operations is undefined.
If an error occurs, a NULL pointer is returned.
If no error occurs, the returned pointer will reflect an allocation aligned to the value
of GL_MIN_MAP_BUFFER_ALIGNMENT basic machine units. Subtracting offset from this returned
pointer will always produce a multiple of the value of GL_MIN_MAP_BUFFER_ALIGNMENT.
The returned pointer values may not be passed as parameter values to GL commands. For
example, they may not be used to specify array pointers, or to specify or query pixel or
texture image data; such actions produce undefined results, although implementations may
not check for such behavior for performance reasons.
Mappings to the data stores of buffer objects may have nonstandard performance
characteristics. For example, such mappings may be marked as uncacheable regions of
memory, and in such cases reading from them may be very slow. To ensure optimal
performance, the client should use the mapping in a fashion consistent with the values of
GL_BUFFER_USAGE for the buffer object and of access. Using a mapping in a fashion
inconsistent with these values is liable to be multiple orders of magnitude slower than
using normal memory.
NOTES
Alignment of the returned pointer is guaranteed only if the version of the GL version is
4.2 or greater. Also, the GL_ATOMIC_COUNTER_BUFFER target is accepted only if the GL
version is 4.2 or greater.
The GL_DISPATCH_INDIRECT_BUFFER and GL_SHADER_STORAGE_BUFFER targets are accepted only if
the GL version is 4.3 or greater.
The GL_QUERY_BUFFER target is available only if the GL version is 4.4 or greater.
The GL_MAP_PERSISTENT_BIT and GL_MAP_COHERENT_BIT flags are available only if the GL
version is 4.4 or greater.
ERRORS
GL_INVALID_ENUM is generated by glMapBufferRange if target is not one of the buffer
binding targets listed above.
GL_INVALID_OPERATION is generated by glMapBufferRange if zero is bound to target.
GL_INVALID_OPERATION is generated by glMapNamedBufferRange if buffer is not the name of an
existing buffer object.
GL_INVALID_VALUE is generated if offset or length is negative, if $offset + length$ is
greater than the value of GL_BUFFER_SIZE for the buffer object, or if access has any bits
set other than those defined above.
GL_INVALID_OPERATION is generated for any of the following conditions:
• length is zero.
• The buffer object is already in a mapped state.
• Neither GL_MAP_READ_BIT nor GL_MAP_WRITE_BIT is set.
• GL_MAP_READ_BIT is set and any of GL_MAP_INVALIDATE_RANGE_BIT,
GL_MAP_INVALIDATE_BUFFER_BIT or GL_MAP_UNSYNCHRONIZED_BIT is set.
• GL_MAP_FLUSH_EXPLICIT_BIT is set and GL_MAP_WRITE_BIT is not set.
• Any of GL_MAP_READ_BIT, GL_MAP_WRITE_BIT, GL_MAP_PERSISTENT_BIT, or
GL_MAP_COHERENT_BIT are set, but the same bit is not included in the buffer's storage
flags.
No error is generated if memory outside the mapped range is modified or queried, but the
result is undefined and system errors (possibly including program termination) may occur.
ASSOCIATED GETS
glGet() with pname GL_MIN_MAP_BUFFER_ALIGNMENT. The value must be a power of two that is
at least 64.
VERSION SUPPORT
┌──────────────────────┬───────────────────────────────────────────────────────────────────────┐
│ │ OpenGL Version │
├──────────────────────┼─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┤
│Function │ 2.0 │ 2.1 │ 3.0 │ 3.1 │ 3.2 │ 3.3 │ 4.0 │ 4.1 │ 4.2 │ 4.3 │ 4.4 │ 4.5 │
│/ │ │ │ │ │ │ │ │ │ │ │ │ │
│Feature │ │ │ │ │ │ │ │ │ │ │ │ │
│Name │ │ │ │ │ │ │ │ │ │ │ │ │
├──────────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
│glMapBufferRange │ - │ - │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │
├──────────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
│glMapNamedBufferRange │ - │ - │ - │ - │ - │ - │ - │ - │ - │ - │ - │ ✔ │
└──────────────────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┘
SEE ALSO
glMapBuffer(), glUnmapBuffer(), glFlushMappedBufferRange(), glBindBuffer(),
glBufferStorage()
COPYRIGHT
Copyright © 2010-2014 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.
http://opencontent.org/openpub/.
COPYRIGHT
Copyright © 2014 Khronos Group
[FIXME: source] 01/03/2018 GLMAPBUFFERRANGE(3G)