title: matrix multiplication with vector in glsl
body: <p>Ref <a href="http://webglfundamentals.org/webgl/lessons/webgl-3d-orthographic.html" rel="nofollow">http://webglfundamentals.org/webgl/lessons/webgl-3d-orthographic.html</a>
  In vector shader there is multiplication of <code>mat4</code> and <code>vec4</code>.</p>
  
  <pre><code>attribute vec4 a_position;
  
  uniform mat4 u_matrix;
  
  void main() {
  
    // Multiply the position by the matrix.
  
    gl_Position = u_matrix * a_position;
  
  }
  </code></pre>
  
  <p>How is it possible to multiply 4*4 matrix with 1*4 matrix?
  Shouldn't it be <code>gl_Position = a_position * u_matrix;</code></p>
  
  <p>Can anybody explain this?</p>