glBeginQuery — delimit the boundaries of a query object
void glBeginQuery( | GLenum target, |
GLuint id); |
target
Specifies the target type of query object established between
glBeginQuery and the subsequent glEndQuery.
The symbolic constant must be one of GL_ANY_SAMPLES_PASSED, GL_ANY_SAMPLES_PASSED_CONSERVATIVE,
or GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN.
idSpecifies the name of a query object.
void glEndQuery( | GLenum target); |
target
Specifies the target type of query object to be concluded.
The symbolic constant must be one of GL_ANY_SAMPLES_PASSED, GL_ANY_SAMPLES_PASSED_CONSERVATIVE,
or GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN.
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_ANY_SAMPLES_PASSED, GL_ANY_SAMPLES_PASSED_CONSERVATIVE,
or GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN. The behavior of the query
object depends on its type and is as follows.
If target is GL_ANY_SAMPLES_PASSED, 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. When
glEndQuery is executed, the samples-passed flag is assigned to the query object's result value. This value can
be queried by calling glGetQueryObjectuiv with pname
GL_QUERY_RESULT.
If target is 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. The implementation
may choose to use a less precision version of the test, which can additionally set the samples-passed flag to GL_TRUE
in some other implementation-dependent cases. When glEndQuery is executed, the samples-passed flag is assigned to
the query object's result value. This value can be queried by calling glGetQueryObjectuiv
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 glGetQueryObjectuiv with pname
GL_QUERY_RESULT.
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. Note: GL_ANY_SAMPLES_PASSED
and GL_ANY_SAMPLES_PASSED_CONSERVATIVE alias to the same target for the purposes of this error.
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 not a name returned from a previous call to
glGenQueries, or if such a name has since been deleted with glDeleteQueries.
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.
Copyright © 2005 Addison-Wesley. 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/.