oracular (3) glBeginQuery.3G.gz
NAME
glBeginQuery - delimit the boundaries of a query object
C SPECIFICATION
void glBeginQuery(GLenum target, GLuint id);
void glEndQuery(GLenum target);
PARAMETERS FOR GLBEGINQUERY
target
Specifies the target type of query object established between glBeginQuery and the subsequent
glEndQuery. The symbolic constant must be one of GL_SAMPLES_PASSED, GL_ANY_SAMPLES_PASSED,
GL_ANY_SAMPLES_PASSED_CONSERVATIVE, GL_PRIMITIVES_GENERATED,
GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN, or GL_TIME_ELAPSED.
id
Specifies the name of a query object.
PARAMETERS FOR GLENDQUERY
target
Specifies the target type of query object to be concluded. The symbolic constant must be one of
GL_SAMPLES_PASSED, GL_ANY_SAMPLES_PASSED, GL_ANY_SAMPLES_PASSED_CONSERVATIVE,
GL_PRIMITIVES_GENERATED, GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN, or GL_TIME_ELAPSED.
DESCRIPTION
glBeginQuery and
glEndQuery delimit the boundaries of a query object. query must be a name previously returned from a
call to glGenQueries(). If a query object with name id does not yet exist it is created with the type
determined by target. target must be one of GL_SAMPLES_PASSED, GL_ANY_SAMPLES_PASSED,
GL_PRIMITIVES_GENERATED, GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN, or GL_TIME_ELAPSED. The behavior of
the query object depends on its type and is as follows.
If target is GL_SAMPLES_PASSED, id must be an unused name, or the name of an existing occlusion query
object. When glBeginQuery is executed, the query object's samples-passed counter is reset to 0.
Subsequent rendering will increment the counter for every sample that passes the depth test. If the value
of GL_SAMPLE_BUFFERS is 0, then the samples-passed count is incremented by 1 for each fragment. If the
value of GL_SAMPLE_BUFFERS is 1, then the samples-passed count is incremented by the number of samples
whose coverage bit is set. However, implementations, at their discression may instead increase the
samples-passed count by the value of GL_SAMPLES if any sample in the fragment is covered. When glEndQuery
is executed, the samples-passed counter is assigned to the query object's result value. This value can be
queried by calling glGetQueryObject() with pname GL_QUERY_RESULT.
If target is GL_ANY_SAMPLES_PASSED or GL_ANY_SAMPLES_PASSED_CONSERVATIVE, id must be an unused name, or
the name of an existing boolean occlusion query object. When glBeginQuery is executed, the query object's
samples-passed flag is reset to GL_FALSE. Subsequent rendering causes the flag to be set to GL_TRUE if
any sample passes the depth test in the case of GL_ANY_SAMPLES_PASSED, or if the implementation
determines that any sample might pass the depth test in the case of GL_ANY_SAMPLES_PASSED_CONSERVATIVE.
The implementation may be able to provide a more efficient test in the case of
GL_ANY_SAMPLES_PASSED_CONSERVATIVE if some false positives are acceptable to the application. When
glEndQuery is executed, the samples-passed flag is assigned to the query object's result value. This
value can be queried by calling glGetQueryObject() with pname GL_QUERY_RESULT.
If target is GL_PRIMITIVES_GENERATED, id must be an unused name, or the name of an existing primitive
query object previously bound to the GL_PRIMITIVES_GENERATED query binding. When glBeginQuery is
executed, the query object's primitives-generated counter is reset to 0. Subsequent rendering will
increment the counter once for every vertex that is emitted from the geometry shader, or from the vertex
shader if no geometry shader is present. When glEndQuery is executed, the primitives-generated counter is
assigned to the query object's result value. This value can be queried by calling glGetQueryObject() with
pname GL_QUERY_RESULT.
If target is GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN, id must be an unused name, or the name of an
existing primitive query object previously bound to the GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN query
binding. When glBeginQuery is executed, the query object's primitives-written counter is reset to 0.
Subsequent rendering will increment the counter once for every vertex that is written into the bound
transform feedback buffer(s). If transform feedback mode is not activated between the call to
glBeginQuery and glEndQuery, the counter will not be incremented. When glEndQuery is executed, the
primitives-written counter is assigned to the query object's result value. This value can be queried by
calling glGetQueryObject() with pname GL_QUERY_RESULT.
If target is GL_TIME_ELAPSED, id must be an unused name, or the name of an existing timer query object
previously bound to the GL_TIME_ELAPSED query binding. When glBeginQuery is executed, the query object's
time counter is reset to 0. When glEndQuery is executed, the elapsed server time that has passed since
the call to glBeginQuery is written into the query object's time counter. This value can be queried by
calling glGetQueryObject() with pname GL_QUERY_RESULT.
Querying the GL_QUERY_RESULT implicitly flushes the GL pipeline until the rendering delimited by the
query object has completed and the result is available. GL_QUERY_RESULT_AVAILABLE can be queried to
determine if the result is immediately available or if the rendering is not yet complete.
NOTES
If the query target's count exceeds the maximum value representable in the number of available bits, as
reported by glGetQueryiv() with target set to the appropriate query target and pname
GL_QUERY_COUNTER_BITS, the count becomes undefined.
An implementation may support 0 bits in its counter, in which case query results are always undefined and
essentially useless.
When GL_SAMPLE_BUFFERS is 0, the samples-passed counter of an occlusion query will increment once for
each fragment that passes the depth test. When GL_SAMPLE_BUFFERS is 1, an implementation may either
increment the samples-passed counter individually for each sample of a fragment that passes the depth
test, or it may choose to increment the counter for all samples of a fragment if any one of them passes
the depth test.
The query targets GL_ANY_SAMPLES_PASSED, and GL_TIME_ELAPSED are availale only if the GL version is 3.3
or higher.
The query target GL_ANY_SAMPLES_PASSED_CONSERVATIVE is available only of the GL version is 4.3 or higher.
ERRORS
GL_INVALID_ENUM is generated if target is not one of the accepted tokens.
GL_INVALID_OPERATION is generated if glBeginQuery is executed while a query object of the same target is
already active.
GL_INVALID_OPERATION is generated if
glEndQuery is executed when a query object of the same target is not active.
GL_INVALID_OPERATION is generated if id is 0.
GL_INVALID_OPERATION is generated if id is the name of an already active query object.
GL_INVALID_OPERATION is generated if id refers to an existing query object whose type does not does not
match target.
VERSION SUPPORT
┌─────────────┬───────────────────────────────────────────────────────────────────────┐
│ │ OpenGL Version │
├─────────────┼─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┤
│Function │ 2.0 │ 2.1 │ 3.0 │ 3.1 │ 3.2 │ 3.3 │ 4.0 │ 4.1 │ 4.2 │ 4.3 │ 4.4 │ 4.5 │
│/ │ │ │ │ │ │ │ │ │ │ │ │ │
│Feature │ │ │ │ │ │ │ │ │ │ │ │ │
│Name │ │ │ │ │ │ │ │ │ │ │ │ │
├─────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
│glBeginQuery │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │
├─────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
│glEndQuery │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │
└─────────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┘
SEE ALSO
glBeginQueryIndexed(), glDeleteQueries(),
glEndQuery, glGenQueries(), glGetQueryObject(), glGetQueryiv(), glIsQuery()
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 Sams Publishing
Copyright © 2010-2014 Khronos Group
[FIXME: source] 04/26/2024 GLBEGINQUERY(3G)