title: 3d object with transparrent material shows as solid black
body: <p>My guns have a certain range. When hovering over one I want to demonstrate what that means. So I've added a 3d-object (a flattened cylinder) which I want to show/hide onMouse-enter/leave.  </p>
  
  <p>But first I need it to be transparent - I've searched and found how - It's materials rendering mode must be transparent, and the color must have an alpha value (here 128).<br>
  <a href="https://i.stack.imgur.com/Mnk17.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Mnk17.png" alt="enter image description here"></a>
  But it looks VERY SOLID BLACK to me...?</p>