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Name
SGIX_async_histogram
Name Strings
GL_SGIX_async_histogram
Version
$Date: 1998/02/11 23:24:25 $ $Revision: 1.3 $
Number
134
Dependencies
SGIX_async is required.
EXT_histogram is required.
Overview
This extension introduces a new asynchronous mode for histogram
and minmax readbacks. It allows programs to get the contents of a
histogram or minmax table without blocking and to continue issuing
graphics commands during the readback.
New Procedures and Functions
None
New Tokens
Accepted by the <cap> parameter of Enable, Disable and IsEnabled,
and by the <pname> parameter of GetBooleanv, GetIntegerv, GetFloatv,
and GetDoublev:
ASYNC_HISTOGRAM_SGIX 0x832C
Accepted by the <pname> parameter of GetBooleanv, GetIntegerv,
GetFloatv, and GetDoublev:
MAX_ASYNC_HISTOGRAM_SGIX 0x832D
Additions to Chapter 2 of the 1.1 Specification (OpenGL Operation)
None
Additions to Chapter 3 of the 1.1 Specification (Rasterization)
Add the following to the end of the specification of histogram and
minmax operators in section 3.6.4 ("Pixel Transfer Operations"):
Calling Enable with the <cap> parameter set to
ASYNC_HISTOGRAM_SGIX causes subsequent GetHistogramEXT and
GetMinmaxEXT commands to be asynchronous (similar to the
asynchronous DrawPixels command described earlier). An
implementation of these asynchronous commands may be non-blocking:
It may return control to the program immediately rather than
waiting for an asynchronous query command's results to be written
into host memory. Asynchronous histogram and minmax readback
commands sample the OpenGL state vector at the time they are
issued, but they may be executed at some undefined point in the
future. In particular, if subsequent commands change the contents
of the histogram or minmax table then the result of the query is
undefined.
Calling Disable with the <cap> parameter set to
ASYNC_HISTOGRAM_SGIX restores the default synchronous behavior.
Additions to Chapter 4 of the 1.1 Specification (Fragments and the
Frame Buffer)
None
Additions to Chapter 5 of the 1.1 Specification (Special Functions)
None
Additions to Chapter 6 of the 1.1 Specification (State and State Requests)
None
Additions to the GLX Specification
None
GLX Protocol
None
Dependencies on SGIX_async
This document adds a new category of asynchronous commands to
the framework defined by SGIX_async.
Dependencies on EXT_histogram
This document changes the semantics of the query commands defined
by EXT_histogram.
Errors
INVALID_OPERATION is generated if GetHistogramEXT or GetMinmaxEXT
is called and ASYNC_HISTOGRAM_SGIX is enabled and the number of
asynchronous histogram or minmax readback commands that have been
issued but not queried (using FinishAsyncSGIX or PollAsyncSGIX)
exceeds MAX_ASYNC_HISTOGRAM_SGIX.
New State
Get Value Get Command Type Value Attrib
--------- ----------- ---- ------- ------
ASYNC_HISTOGRAM_SGIX IsEnabled B False enable
New Implementation Dependent State
Minimum
Get Value Get Command Type Value
--------- ----------- ---- -------
MAX_ASYNC_HISTOGRAM_SGIX GetIntegerv Z+ 1