title: How to plot a 3D figure in matlab based on a function like f(x,y,z)=0?
body: <p>How to plot a 3D figure in <code>MATLAB</code> based on a function like <code>f(x,y,z)=0</code>? 
  And this complicated function can not be written as <code>z = f(x,y)</code>. </p>
  
  <pre><code>f(x,y,z)=sum(a.*exp(sv(:,1)-x).^2+sv(:,2)-y).^2+sv(:,3)-z).^2)-b=0
  </code></pre>
  
  <p>where a is a known vector, sv is a known matrix, b is a known value. x,y,z are three variables. How to draw this surface in 3D way in matlab?</p>