I created a canvas of world space where I put the image. At the top of this image, I place the material with the custom shader that I found there http://answers.unity3d.com/questions/878667/world-space-canvas-on-top-of-everything.html
This works great, unless I get close to a large object, my user interface will disappear. When I clean the occlusion, it works well. The problem is that my UICanvas and my image are not marked as “static”. I also tried to bake when my user interface canvas was disabled and I still have the same problem.
The shader used by my user interface elements has "Cull Off".
How it should be (occlusion is not baked): 
( ): 
: http://imgur.com/a/r5Ksc
UICanvas (y > 0), .
, ?