Not much to say here. I had a bit of inspiration, remembering a Christoph Hormann tutorial http://www.imagico.de/pov/icons.html on making transparent icons in povray and realized that what he was describing was the final piece in the povray for viewsheds milleau: no_image option for an object forces it to interact with the scene in every way, but to be seen by the camera. I’ll post the revised code coming up, but it’s pretty simple. Add the following option inside the code to the tree object:
no_image .

http://www.povray.org/documentation/view/3.6.1/328/