Face

– If no vertex falls over an obstacle, the obstacle is not detected as a collider.
– In these cases face can be used for collision detection but makes solver really slow.

– As you can see, no vertex falls over the upper face of the obstacle. So the obstacle is not detected as a collider if the checkbox ‘Face’ is not enabled.

Blender Soft Body Edges Face Top View

Blender Soft Body Edges Face