The glass material in one of my scenes is not rendering as expected. It is a simple shadowless glass material I have used countless times. In an attempt to track down the reason, I created a duplicate of an existing scene (GlassCorrect.blend) in which the shader is working and deleted every object except for an eyeball with a glass shell, lights and a camera. Then I created a duplicate of my problem scene (GlassIncorrect.blend), deleted all objects and the world, and appended the objects and world from the first scene. The glass is rendering without any transparency, just reflecting the world around it. Please help me figure out what is going wrong.