title: How could you create a ultrasonic vision in Unity3d? (Bat Vision)
body: <p>I had the idea to create a game where you would see everything like a bat. There are some <a href="https://www.youtube.com/watch?v=BWDbc2l8YlE" rel="nofollow noreferrer">people</a> which have achieved something like that.</p>
  
  <p>The problem is I would like to have another type of "Bat Vision". It is pretty hard to explain but if i look into one direction and then rotate the character I would still see something I looked at before. </p>
  
  <p><strong>Explanation with timestamps:</strong></p>
  
  <ul>
  <li>Sec 0: I am looking at point A where a object is 300 meters away</li>
  <li>Sec 1: I rotate to point B and see an object 100 meters away</li>
  <li>Sec 2: I see object A and B at the same time</li>
  <li>Sec 3: I still see object B</li>
  </ul>
  
  <p><strong>Explanation with picture:</strong>
  <a href="https://i.stack.imgur.com/zbiVR.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/zbiVR.png" alt="enter image description here"></a>
  As you can see the player first shoots the ultrasonic waves <em>a</em> first on <em>A</em> and afterwards waves <em>b</em> on <em>B</em>. They both come back at the same time so that both objects are seen at the same time.</p>
  
  <p>If you did not understand why I see objects delayed. As everyone knows sound travels with a speed about 1/3 km/s. So an object which is 300 meters in the distance would get seen after about 2 sec. </p>
  
  <p>I already tried to shoot <code>RayCasts</code> or <code>GameObjects</code> into the direction and as further they are away the darker the pixel at that position will be. But as you can think... Shooting 2 million <code>RayCasts</code> every Frame is not very healthy. I was also thinking about <code>Shaders</code> but I don't know how it is possible that one still sees the <code>Shaders</code> while looking into another direction. Also I don't have much experience with <code>Shaders</code> and would need help there anyways.</p>
  
  <p>I would be glad if someone has another Idea how I could create this.</p>