I'm trying to create a nice planet with good atmosphere. I've made three concentric spheres, the smallest a planet skin, the next two slightly bigger than the last and i intend them to have camera facing shaders, so that the atmosphere is thickest around teh edges. I had managed this once in 4.0 but forgot how I did it. I'm in 5 now and a bit fuzzy on the use of render nodes for this. Any ideas?

Thanks..