This is something interesting about how Revit deals with Model Fill Patterns. When you have fill patterns applied to elements in your model, at different scales it will be represented differently, and 1:100 is usually the magic number before visual changes take place.
As the scale increases, Revit will halftone your fill pattern or even change its representation to a solid fill. This is to do with how close the lines are in your fill pattern and the scale of the view.
The Example below is a brick wall, with the model fill pattern to indicate the brickwork. As you increase the view scale it changes from black lines at scales up to 1:100, to halftone at 1:250, to a halftone solid fill at 1:1000.
Different fill patterns with different line spacing’s will give you varying results. It is just good to know that Revit is going to make these changes to your fill, whether you like it or not.