So I really wanted to use cycles for an upcoming animation project, but was disappointed to find out cycles didn’t have a way to animate an object’s opacity like you can in Blender Internal. I think I have found a way to do it in cycles using material nodes as shown below. By adjusting the Fac value of the leftmost Mix Shader node to 0, you can effectively make it invisible. The key was also making the color of the Transparent Shader node have an alpha value of 0. With this setup you could just keyframe the Fac value of the leftmost Mix Shader node and animate an object’s visibility. This is good for when you want to fade something onscreen in place or fade it out.
I know someone may have figured this out already but I thought it was a simple way to achieve it and I also could not find anything on google showing me how I could animate visibility with cycles. Hope this helps someone out there!! Enjoy
-In Search Graphics