Very often in visual effects you’ve got to deal with shadows. If you’re adding a CG object or character to a scene, it’s almost certain that somewhere else in that scene it’s going to be casting a shadow. This is typically dealt with by using a shadow pass, one of the many render passes you can output when rendering. In Blender, the shadow pass usually entails a little bit of work in the compositor to setup. There’s multiple ways to do it, and if you use the camera tracker and the scene setup, the nodes will even be created for you.
However, there’s an easier way being developed. The shadow catcher object. This feature is still heavily under development and many features aren’t yet completed (or even started!). In fact, this may be one of the first builds available for testing. But it’s out there, so I gave it a shot. The goal is to make setting up shadows much easier and faster, and to be able to use those shadows right in the rendered viewport.
Check out the video below to see how to start testing it out and playing around with it. So far I’ve only seen Windows builds, so if you know of a Linux or Mac build, please post in the comments and I’ll update the post.
Most recent Windows build (10-5-16):
GraphicAll Shadow Catcher build
Previous Windows build (8-31-16):
Build 1 (Thanks tungerz!)
EDIT: It turns out that the problem in the video where the cylinder emission light is causing the ground plane to become dark is simply a matter of the the green metal sphere casting a shadow on the entire plane. Moving the emission cylinder shows this, see the screenshot below.