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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 pnameGL_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
pnameGL_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
pnameGL_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 pnameGL_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
pnameGL_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 pnameGL_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] 07/22/2015 GLBEGINQUERY(3G)