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<?xml version="1.0" encoding="UTF-8"?>
<extension href="EXT_disjoint_timer_query_webgl2/">
<name>EXT_disjoint_timer_query_webgl2</name>
<contact> <a href="https://www.khronos.org/webgl/public-mailing-list/">WebGL
working group</a> (public_webgl 'at' khronos.org) </contact>
<contributors>
<contributor>Contributors to ARB_occlusion_query</contributor>
<contributor>Contributors to EXT_timer_query</contributor>
<contributor>Contributors to ARB_timer_query</contributor>
<contributor>Ben Vanik, Google Inc.</contributor>
<contributor>Daniel Koch, TransGaming Inc.</contributor>
<contributor>Florian Boesch (pyalot 'at' gmail.com)</contributor>
<contributor>Members of the WebGL working group</contributor>
</contributors>
<number>33</number>
<depends>
<api version="2.0"/>
</depends>
<overview>
<mirrors href="http://www.khronos.org/registry/gles/extensions/EXT/EXT_disjoint_timer_query.txt"
name="EXT_disjoint_timer_query">
<addendum>
Specifies that queries' results only become available at certain well-defined times.
</addendum>
</mirrors>
<features>
<feature>
This extension provides the same functionality as <a
href="../EXT_disjoint_timer_query/">EXT_disjoint_timer_query</a>. The IDL, description, and
extension name are specialized for WebGL 2.0, which incorporates query objects into the core
specification.
</feature>
</features>
</overview>
<idl xml:space="preserve">
typedef unsigned long long GLuint64EXT;
[NoInterfaceObject]
interface EXT_disjoint_timer_query_webgl2 {
const GLenum QUERY_COUNTER_BITS_EXT = 0x8864;
const GLenum TIME_ELAPSED_EXT = 0x88BF;
const GLenum TIMESTAMP_EXT = 0x8E28;
const GLenum GPU_DISJOINT_EXT = 0x8FBB;
void queryCounterEXT(WebGLQuery query, GLenum target);
};
</idl>
<newtok>
<function name="beginQuery" type="">
<param name="target" type="GLenum"/>
<param name="query" type="WebGLQuery?"/>
<code>target</code> accepts <code>TIME_ELAPSED_EXT</code>.
</function>
</newtok>
<newtok>
<function name="endQuery" type="void">
<param name="target" type="GLenum"/>
<code>target</code> accepts <code>TIME_ELAPSED_EXT</code>.
</function>
</newtok>
<newfun>
<function name="queryCounterEXT" type="void">
<param name="query" type="WebGLQuery"/>
<param name="target" type="GLenum"/>
<code>target</code> accepts <code>TIMESTAMP_EXT</code>.
</function>
</newfun>
<newtok>
<function name="getQuery" type="any">
<param name="target" type="GLenum"/>
<param name="pname" type="GLenum"/>
<code>target</code> and <code>pname</code> accept the following combinations of
parameters. The return type of this method now depends on the parameter queried.
<br/>
<table width="30%">
<tr><th>target</th><th>pname</th><th>returned type</th></tr>
<tr><td>TIME_ELAPSED_EXT</td><td>CURRENT_QUERY</td><td>WebGLQuery?</td></tr>
<tr><td>TIMESTAMP_EXT</td><td>CURRENT_QUERY</td><td>null</td></tr>
<tr><td>TIME_ELAPSED_EXT</td><td>QUERY_COUNTER_BITS_EXT</td><td>GLint</td></tr>
<tr><td>TIMESTAMP_EXT</td><td>QUERY_COUNTER_BITS_EXT</td><td>GLint</td></tr>
</table>
</function>
</newtok>
<newtok>
<function name="getParameter" type="any">
<param name="pname" type="GLenum"/>
<code>pname</code> accepts <code>TIMESTAMP_EXT</code> or <code>GPU_DISJOINT_EXT</code>.
<br/>
The return type depends on the parameter queried:
<table width="30%">
<tr><th>pname</th><th>returned type</th></tr>
<tr><td>TIMESTAMP_EXT</td><td>GLuint64EXT</td></tr>
<tr><td>GPU_DISJOINT_EXT</td><td>boolean</td></tr>
</table>
</function>
</newtok>
<samplecode xml:space="preserve">
<pre>
// Example (1) -- uses beginQuery/endQuery.
var ext = gl.getExtension('EXT_disjoint_timer_query_webgl2');
var query = gl.createQuery();
gl.beginQuery(ext.TIME_ELAPSED_EXT, query);
// Draw object
gl.drawElements(...);
gl.endQuery(ext.TIME_ELAPSED_EXT);
// ...at some point in the future, after returning control to the browser and being called again:
var available = gl.getQueryParameter(query, gl.QUERY_RESULT_AVAILABLE);
var disjoint = gl.getParameter(ext.GPU_DISJOINT_EXT);
if (available && !disjoint) {
// See how much time the rendering of the object took in nanoseconds.
var timeElapsed = gl.getQueryParameter(query, gl.QUERY_RESULT);
// Do something useful with the time. Note that care should be
// taken to use all significant bits of the result, not just the
// least significant 32 bits.
adjustObjectLODBasedOnDrawTime(timeElapsed);
}
//----------------------------------------------------------------------
// Example (2) -- same as the example above, but uses queryCounterEXT instead.
var ext = gl.getExtension('EXT_disjoint_timer_query_webgl2');
var startQuery = gl.createQuery();
var endQuery = gl.createQuery();
ext.queryCounterEXT(startQuery, ext.TIMESTAMP_EXT);
// Draw object
gl.drawElements(...);
ext.queryCounterEXT(endQuery, ext.TIMESTAMP_EXT);
// ...at some point in the future, after returning control to the browser and being called again:
var available = gl.getQueryParameter(endQuery, gl.QUERY_RESULT_AVAILABLE);
var disjoint = gl.getParameter(ext.GPU_DISJOINT_EXT);
if (available && !disjoint) {
// See how much time the rendering of the object took in nanoseconds.
var timeStart = gl.getQueryParameter(startQuery, gl.QUERY_RESULT);
var timeEnd = gl.getQueryParameter(endQuery, gl.QUERY_RESULT);
// Do something useful with the time. Note that care should be
// taken to use all significant bits of the result, not just the
// least significant 32 bits.
adjustObjectLODBasedOnDrawTime(timeEnd - timeStart);
}
//----------------------------------------------------------------------
// Example (3) -- check the number of timestamp bits to determine how to best
// measure elapsed time.
var ext = gl.getExtension('EXT_disjoint_timer_query_webgl2');
var timeElapsedQuery;
var startQuery;
var endQuery;
var useTimestamps = false;
if (gl.getQuery(ext.TIMESTAMP_EXT, ext.QUERY_COUNTER_BITS_EXT) > 0) {
useTimestamps = true;
}
// Clear the disjoint state before starting to work with queries to increase
// the chances that the results will be valid.
gl.getParameter(ext.GPU_DISJOINT_EXT);
if (useTimestamps) {
startQuery = gl.createQuery();
endQuery = gl.createQuery();
ext.queryCounterEXT(startQuery, ext.TIMESTAMP_EXT);
} else {
timeElapsedQuery = gl.createQuery();
gl.beginQuery(ext.TIME_ELAPSED_EXT, timeElapsedQuery);
}
// Draw object
gl.drawElements(...);
if (useTimestamps) {
ext.queryCounterEXT(endQuery, ext.TIMESTAMP_EXT);
} else {
gl.endQuery(ext.TIME_ELAPSED_EXT);
}
// ...at some point in the future, after returning control to the browser and being called again:
var disjoint = gl.getParameter(ext.GPU_DISJOINT_EXT);
if (disjoint) {
// Have to redo all of the measurements.
} else {
var available;
if (useTimestamps) {
available = gl.getQueryParameter(endQuery, gl.QUERY_RESULT_AVAILABLE);
} else {
available = gl.getQueryParameter(timeElapsedQuery, gl.QUERY_RESULT_AVAILABLE);
}
if (available) {
var timeElapsed;
if (useTimestamps) {
// See how much time the rendering of the object took in nanoseconds.
var timeStart = gl.getQueryParameter(startQuery, gl.QUERY_RESULT);
var timeEnd = gl.getQueryParameter(endQuery, gl.QUERY_RESULT);
timeElapsed = timeEnd - timeStart;
} else {
timeElapsed = gl.getQueryParameter(query, gl.QUERY_RESULT);
}
// Do something useful with the time. Note that care should be
// taken to use all significant bits of the result, not just the
// least significant 32 bits.
adjustObjectLODBasedOnDrawTime(timeElapsed);
}
}
</pre>
</samplecode>
<history>
<revision date="2016/09/30">
<change>Split WebGL 2.0 specification of this extension into its own file
for better comprehensibility.</change>
</revision>
<revision date="2016/10/11">
<change>Fixed errors in sample code pointed out by @juj.</change>
</revision>
</history>
</extension>
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