The ROBLOX team brings you another exciting release with awesome graphics improvements! Presenting: ambient shadows!
Ambient shadows are shadows that are created from ambient (as opposed to direct) light. With ambient shadows on, you will notice that the corners of rooms are darker, as well as areas where two parts are close together (like the top of the stairs in the following screenshot).
You will the see the new shadows in all ROBLOX levels if you have a mid-to-high range graphics card. Shadows are a computationally taxing. For complicated levels with a lot of bricks you may see shadows turn on, and then turn off if ROBLOX notices shadows is dropping your framerate below 30 FPS.