blob: 23fda418a2d8e4249d71199ba771708907259a33 [file] [log] [blame]
XXX - incomplete
Name Strings
$Date: 1998/06/17 19:59:07 $ $Revision: 1.4 $
SGIX_instruments is required
SGIX_multisample affects the definition of this extension.
This extension defines behavior for instruments which are
maintained on the Bali R chips. The behavior is different from
standard instruments behavior since each system may contain more
than one R chip.
Additionally, this extension defines two such instruments: one to
count the number of fragments generated and a second to count the
number of fragments which passed the depth test.
* Should fragments generated by internal pixel operations be
counted? From a GL point of view they don't exist, but from
an R usage point of view they do.
* Should we expose the texture cache wait counter? What could
the user do about a bottleneck caused by texture cache misses?
* Currently we count only fragments which passed the depth test
and do not count fragments which were drawn when the depth
test was disabled. Is this the correct behavior?
* Are there any other R instruments we should add?
New Procedures and Functions
New Tokens
Accepted by the <cap> parameter of Enable, Disable and IsEnabled:
Accepted by the <pname> parameter of GetBooleanv, GetIntegerv,
GetFloatv, and GetDoublev:
Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation)
Additions to Chapter 3 of the 1.0 Specification (Rasterization)
Additions to Chapter 4 of the 1.0 Specification (Per-Fragment Operations
and the Frame Buffer)
Add to section 4.1 after the introductory paragraph and prior to
section 4.1.1 (Pixel Ownership Test):
instruments have been started via a call to StartInstrumentsSGIX,
a counter of the number of fragments generated is maintained.
This counter is incremented by one for each fragment. The GL
implementation is not guaranteed to generate a fragment for every
screen pixel which the primitive touched as long as this
optimization will not affect the final image. For example, if a
region of the primitive only contains fragments which the GL has
determined will fail the Z test, the fragments may not be
generated. Therefore, the count of fragments generated may be
smaller than but may not be greater than the screen space area of
the primitive as determined by the number of pixels touched by the
Added to subsection 4.1.5 (Depth buffer test) at the end of the
paragraph which begins "If the depth buffer test fails...":
If BALI_DEPTH_PASS_INSTRUMENT is enabled and instruments have been
started via a call to StartInstrumentSGIX, a counter of the number
of fragments which have passed the depth test is maintained. This
counter is incremented by one for each fragment which passes the
depth test. If MULTISAMPLE_SGIS is enabled, the counter is
incremented by one for each fragment containing at least one
sample for which the depth test passed.
Additions to Chapter 5 of the 1.0 Specification (Special Functions)
Add to the end of section 5.X entitled Instruments:
For instruments which are computed on the Bali R chip, one
response will be returned to the buffer per R chip. The number of
R chips is queried using the enum BALI_R_CHIP_COUNT (see Chapter
6). From the point of view of this extension, the R chips are
considered to be completely interchangable and no mechanism for
identifying which response came from which R chip is provided.
Generally, the application should combine the results from all the
R chips together (for example, by adding them) before using the
Each call to StopInstrumentsSGIX or ReadInstrumentsSGIX will
generate one response per R chip for each enabled R chip
instrument. This count will be reflected in the return values of
glGetInstrumentSGIX. The values from each R chip do not
necessarily return at the same time, so the glGetInstrumentsSGIX
call may return a value from 0 to BALI_R_CHIP_COUNT times the sum
in words of the size of the instrument. However, the values from
each R are returned atomically from the point of view of
glGetInstrumentsSGIX so the return value must be a multiple of the
size in words of the instrument.
If more than one R instrument is enabled and ReadInstrumentsSGIX
or StopInstrumentsSGIX is called, no guarantees are made with
regard to the ordering and interleaving of the reply packets from
the R chips. The instrument response packets from a single R chip
may or may not be placed consecutively in the buffer. Conversely,
the responses from different R chips for a single instrument may
or may not be placed consecutively in the buffer. Also, no
assumptions may be made about which R chip generated which
and BALI_DEPTH_PASS_INSTRUMENT_SGIX instruments uses 4 words of
the buffer. The first word (index 0) will be the enum name of the
BALI_DEPTH_PASS_INSTRUMENT_SGIX). The second word (index 1) of
the instrument is the size in words of all the data returned by
the instrument, which is four for the instruments defined in this
extension. The third word (index 2) will be the instrument
value. Computation of the instrument values is described in
Chapter 3 (Rasterization). The fourth word (index 3) will contain
the marker passed to StopInstrumentsSGIX or ReadInstrumentsSGIX.
Additions to Chapter 6 of the 1.0 Specification (State and State Requests)
Additions to the GLX Specification
New State
New Implementation Dependent State
Get Value Get Command Type Minimum Value
--------- ----------- ---- -------------
BALI_R_CHIP_COUNT GetIntegerv Z+ 1