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GLMAPBUFFER(3G) | [FIXME: manual] | GLMAPBUFFER(3G) |
NAME¶
glMapBuffer, glMapNamedBuffer - map all of a buffer object's data store into the client's address spaceC SPECIFICATION¶
void *glMapBuffer(GLenum target,
GLenum access);
void *glMapNamedBuffer(GLuint buffer,
GLenum access);
PARAMETERS¶
targetSpecifies the target to which the buffer object is bound
for glMapBuffer, 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
glMapNamedBuffer.
access
Specifies the access policy for glMapBuffer and
glMapNamedBuffer, 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 GL_READ_ONLY,
GL_WRITE_ONLY, or GL_READ_WRITE.
DESCRIPTION¶
glMapBuffer and glMapNamedBuffer map the entire data store of a specified buffer object into the client's address space. The data can then be directly read and/or written relative to the returned pointer, depending on the specified access policy. A pointer to the beginning of the mapped range is returned once all pending operations on that buffer object have completed, and may be used to modify and/or query the corresponding range of the data store according to the value of access:•GL_READ_ONLY indicates that the returned
pointer may be used to read buffer object data.
•GL_WRITE_ONLY indicates that the returned
pointer may be used to modify buffer object data.
•GL_READ_WRITE indicates that the returned
pointer may be used to read and to modify buffer object data.
If an error is generated, 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.
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.
No GL error is generated if the returned pointer is accessed in a way
inconsistent with access (e.g. used to read from a mapping made with
accessGL_WRITE_ONLY or write to a mapping made with
access GL_READ_ONLY), but the result is undefined and system
errors (possibly including program termination) may occur.
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 available 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.ERRORS¶
GL_INVALID_ENUM is generated by glMapBuffer if target is not one of the buffer binding targets listed above. GL_INVALID_OPERATION is generated by glMapBuffer if zero is bound to target. GL_INVALID_OPERATION is generated by glMapNamedBuffer if buffer is not the name of an existing buffer object. GL_INVALID_ENUM is generated if access is not GL_READ_ONLY, GL_WRITE_ONLY, or GL_READ_WRITE. GL_OUT_OF_MEMORY is generated 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. GL_INVALID_OPERATION is generated if the buffer object is in a mapped state.ASSOCIATED GETS¶
glGetBufferPointerv() with argument GL_BUFFER_MAP_POINTER glGetBufferParameter() with argument GL_BUFFER_MAPPED, GL_BUFFER_ACCESS, or GL_BUFFER_USAGE 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 |
glMapBuffer | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
glMapNamedBuffer | - | - | - | - | - | - | - | - | - | - | - | ✔ |
SEE ALSO¶
glBindBuffer(), glBindBufferBase(), glBindBufferRange(), glBufferData(), glBufferSubData(), glDeleteBuffers(), glMapBufferRange(), glUnmapBuffer()COPYRIGHT¶
Copyright © 2005 Addison-Wesley. 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 © 2005 Addison-Wesley Group08/26/2014 | [FIXME: source] |