title: Plotting with three independent variables in Matlab
body: <p>I want to plot a 3d function, say u(x,y,z), where all the variables are independent. Can anyone help me out?</p>
  
  <p>Note : The existing so-called 3d plotting functions usually employ two independent variables and a third dependent one.</p>
  
  <p>For example,
  x and y are defined independently, and z = x^2 + y^2. Whereas in my case, even z is also an independent variable, and I want to plot u(x,y,z) = x^2 + y^2 + z^2.</p>