glMapBufferRange man page on RedHat
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GLMAPBUFFERRANGE(3G) OpenGL Manual GLMAPBUFFERRANGE(3G)
NAME
glMapBufferRange - map a section of a buffer object's data store
C SPECIFICATION
void *glMapBufferRange(GLenum target, GLintptr offset,
GLsizeiptr length, GLbitfield access);
PARAMETERS
target
Specifies a binding to which the target buffer is bound.
offset
Specifies a the starting offset within the buffer of the range to
be mapped.
length
Specifies a length of the range to be mapped.
access
Specifies a combination of access flags indicating the desired
access to the range.
DESCRIPTION
glMapBufferRange maps all or part of the data store of a buffer object
into the client's address space. target specifies the target to which
the buffer is bound and must be one of GL_ARRAY_BUFFER,
GL_ATOMIC_COUNTER_BUFFER, GL_COPY_READ_BUFFER, GL_COPY_WRITE_BUFFER,
GL_DRAW_INDIRECT_BUFFER, GL_DISPATCH_INDIRECT_BUFFER,
GL_ELEMENT_ARRAY_BUFFER, GL_PIXEL_PACK_BUFFER, GL_PIXEL_UNPACK_BUFFER,
GL_TEXTURE_BUFFER, GL_TRANSFORM_FEEDBACK_BUFFER, GL_UNIFORM_BUFFER or
GL_SHADER_STORAGE_BUFFER. offset and length indicate the range of data
in the buffer object htat 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.
If no error occurs, a pointer to the beginning of the mapped range is
returned once all pending operations on that buffer have completed, and
may be used to modify and/or query the corresponding range of the
buffer, 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.
Furthermore, 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 sub- sequent 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. 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, glMapBufferRange returns a NULL pointer. If no
error occurs, the returned pointer will reflect an alignment of at
least GL_MIN_MAP_BUFFER_ALIGNMENT basic machine units. The value of
GL_MIN_MAP_BUFFER_ALIGNMENT can be retrieved by calling glGet() with
pname set to GL_MIN_MAP_BUFFER_ALIGNMENT and must be a power of two
that is at least 64. Subtracting offset from this returned pointed will
always produce a multiple of GL_MIN_MAP_BUFFER_ALINMENT.
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.
ERRORS
GL_INVALID_VALUE is generated if either of offset or length is
negative, or if offset + length is greater than the value of
GL_BUFFER_SIZE.
GL_INVALID_VALUE is generated if access has any bits set other than
those defined above.
GL_INVALID_OPERATION is generated for any of the following conditions:
· The buffer is already in a mapped state.
· Neither GL_MAP_READ_BIT or 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.
GL_OUT_OF_MEMORY is generated if glMapBufferRange fails because memory
for the mapping could not be obtained.
SEE ALSO
glMapBuffer(), glFlushMappedBufferRange(), glBindBuffer()
COPYRIGHT
Copyright © 2010-2012 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/.
AUTHORS
opengl.org
opengl.org 03/16/2013 GLMAPBUFFERRANGE(3G)
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