How to simulate convex lens and concave lens?

I am simulating convex and concave lens, is there any shader available?
Please help me.
Thanks in advance.

i dont know about the shader but a tried some method the generate convex or concave effect.

  1. Create a render texture.
  2. Add a camera and use the above created render texture as renderer in camera.
  3. create a new material (Unlit->Texture). Enter the above render texture as its texture.
  4. Apply this material on the object on which you want the effect.
    Hope this might work for you !!!