title: WebGL Flat Shading
body: <p>I have a vertex shader and fragment shader using the <code>flat</code> qualifier, and for complicated hacky reasons explained near the end of <a href="https://www.youtube.com/watch?v=l6PEfzQVpvM" rel="nofollow noreferrer">https://www.youtube.com/watch?v=l6PEfzQVpvM</a>, I want to change the WebGL flat shading provoking vertex, which is the vertex number that WebGL will use when passing varying colors. (my shader is like this):</p>
  
  <pre><code>// ...
  flat out vec3 pass_vertexColor;
  // ...
  </code></pre>
  
  <p>and I know in OpenGL you can change the provoking vertex like this:</p>
  
  <pre><code>glProvokingVertex(1 /* 2, 3 */); // i think
  </code></pre>
  
  <p>But I don't think there is an equivalent in WebGL yet. So my question is:</p>
  
  <p><strong>What is the default WebGL Provoking Vertex?</strong></p>