Help with the physics of optical illusions

You really need to do something, anything, yourself before we can help

 

That's becasue it's not physics- it's how the brain decodes the images in an effort to make sense.

 

Exactly right, it's all about the psychology of human perception and brain processing. An interesting enough topic all to itself.

 

I don't know which illusion you are using, but here's a really simple example:

Say you have a glass of water with a straw in it.

Why does the straw get "cut" sometimes? Does the angle of the straw matter? Does the angle of the light? What about the angle of the viewer? Does the same thing happen with sound?

 

Is that really an 'optical illusion'? I'm not so sure... It looks odd, but I think it's a little different from cognitive illusions:

http://www.world-mysteries.com/illusions/sci_illusions3.htm

The OP did not give us the images (s)he is trying to explain

 

Can you show us the images you plan to use? We can't really help you unless you do that.