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---
title: WebGL2RenderingContext.beginTransformFeedback()
slug: Web/API/WebGL2RenderingContext/beginTransformFeedback
tags:
- API
- WebGL
- WebGL2
- 参考
- 实验性
- 方法
translation_of: Web/API/WebGL2RenderingContext/beginTransformFeedback
---
<div>{{APIRef("WebGL")}} {{SeeCompatTable}}</div>
<p><a href="/en-US/docs/Web/API/WebGL_API">WebGL 2 API</a> 的 <strong><code>WebGL2RenderingContext.beginTransformFeedback()</code></strong> 方法开始一个变换回传（Transform Feedback）操作。</p>
<h2 id="语法">语法</h2>
<pre class="syntaxbox">void <var>gl</var>.beginTransformFeedback(<var>primitiveMode</var>);
</pre>
<h3 id="参数">参数</h3>
<dl>
<dt><code>primitiveMode</code></dt>
<dd>A {{domxref("GLenum")}} specifying the output type of the primitives that will be recorded into the buffer objects that are bound for transform feedback. 可能的值：
<ul>
<li><code>gl.POINTS</code></li>
<li><code>gl.LINES</code></li>
<li><code>gl.TRIANGLES</code></li>
</ul>
</dd>
</dl>
<h3 id="返回值">返回值</h3>
<p>无。</p>
<h2 id="示例">示例</h2>
<pre class="brush: js">var transformFeedback = gl.createTransformFeedback();
gl.bindTransformFeedback(gl.TRANSFORM_FEEDBACK, transformFeedback);
gl.beginTransformFeedback(gl.TRIANGLES);
gl.drawArrays(gl.TRIANGLES, 0, 3);
</pre>
<h2 id="规范">规范</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specification</th>
<th scope="col">Status</th>
<th scope="col">Comment</th>
</tr>
<tr>
<td>{{SpecName('WebGL2', "#3.7.15", "beginTransformFeedback")}}</td>
<td>{{Spec2('WebGL2')}}</td>
<td>WebGL中初次定义。</td>
</tr>
<tr>
<td>{{SpecName('OpenGL ES 3.0', "glBeginTransformFeedback.xhtml", "glBeginTransformFeedback")}}</td>
<td>{{Spec2('OpenGL ES 3.0')}}</td>
<td>OpenGL API 页面。</td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<p>{{Compat("api.WebGL2RenderingContext.beginTransformFeedback")}}</p>
<h2 id="相关链接">相关链接</h2>
<ul>
<li>{{domxref("WebGLTransformFeedback")}}</li>
</ul>
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