Border around reflection pass I am trying to set up a mix of live footage and 3d rendering, but I keep failing in obtaining a realistic reflection layer.

My workflow is to have a ground plane that is totally white, a white sky, and five the plane some degree of reflection (here in the screenshot it is 1.0, but it's only to show the problem, I know it's not realistic this way).
Then i multiply the reflection layer with the result of movieclip+foreground, but I keep having this annoying border around the plane.

How can I get rid of it?
AFAIK, a Dilate/Erode node is commonly used to fix such issue.

Becides, it seems that you set the robot Layer as Mask layer for the reflect RenderLayer, which caused part of the plane was masked as transparent. Try untoggle that in RenderLayer setting, or add a new RenderLayer to get an expected alpha.