table of contents
GLMAPBUFFERRANGE(3G) | [FIXME: manual] | GLMAPBUFFERRANGE(3G) |
NAME¶
glMapBufferRange, glMapNamedBufferRange - map all or part of a buffer object's data store into the client's address spaceC SPECIFICATION¶
void *glMapBufferRange(GLenum target,
GLintptr offset, GLsizeiptr length,
GLbitfield access);
void
*glMapNamedBufferRange(GLuint buffer,
GLintptr offset, GLsizei length,
GLbitfield access);
PARAMETERS¶
targetSpecifies 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
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 |
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 pnameGL_MIN_MAP_BUFFER_ALIGNMENT. The value must be a power of two that is at least 64.VERSION SUPPORT¶
OpenGL Version | ||||||||||||
Function / Feature Name | 2.0 | 2.1 | 3.0 | 3.1 | 3.2 | 3.3 | 4.0 | 4.1 | 4.2 | 4.3 | 4.4 | 4.5 |
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 Group08/26/2014 | [FIXME: source] |