does anybody know how to hide an object but still have it to where in the final render, it still reflects and raytraces the objects around it? Thanks in advance! Boss needs a globe with snow in it but I need the objects rendered seperatly but still retain their effects.
In the attributes editor of an object, find the "Render Stats" section and untick "Primary Visibility." Now this object will be visible to rays (reflections, refractions, etc.), but invisible to the camera and will not render out (except in reflections and refractions, of course.)
This scenario is quite common when for instance, you have a shiny chrome object, but only looks chrome when it's reflecting something in Raytracing, but you still need to comp the object separately for color-correct or what have you. There are a number of useful render stats that come in handy as well, ie., Not Seen in reflections.
another method if rendering with mental ray is (and its handy if you have 200+ elements!!) - group all the bits you just want to have reflections for and in the group node's mentalray/flags menu simply turn off "derive from maya" then turn off the "visible" so it reads "NO" as opposed to "USE INHERITED"
unfortunately it doesn't create a matte cutout in your render (I usually render off a sep pass for animation anyhow) but its very handy when you've literally hundreds of elements in a scene - you can just group them all and have them controlled by one node :D