title: Creating a 3D HUD in unity
body: <p>I am making a space racing game in unity where the race tracks are tunnels which have intricate 3d paths. I want to create an HUD element which gives the player an idea of where she is on the track. I cannot do this by showing only a 2-D projection of the track in the HUD - I need to display the track in 3D.</p>
  
  <p>Let's assume the whole track is one mesh. One idea I had is to create a game object copy of that mesh in a very small size (apply a simple translucent material/shader), and place that object visible in the corner of the camera, as its child object. My problem is that the track can be very large, and I only want to display a part of it at any time. A 3-D masking solution would be perfect - I could use a sphere as a mask. </p>
  
  <p>Is there any way to do this? The nearest thing I found was an UI mask, but that only works on objects on UI canvas, and I can't put a mesh there.</p>
  
  <p>Thanks!</p>