"To actually make the light come from behind we need a black centered light map , with bright edges." That's the point. The background image shows the sun behind the object, or in some cases, people. What we see is an object lit from the front. That's why you can't just take the middle of your pano and put it in back of your scene - it's actually lighting the front of your scene. That's why you need to put what goes in the back behind the main object. This is the sides of the pano and the edges of the problight. Think of the pano as actually being in a ring around the object, casting light. The middle is directly in front of the object, and the edges meet behind it. So it's a 180 degree shift along the pano. But you're turning. So it's a mirror image - the right is now on the left and the left is on the right. At least, that's my understanding.