For models where adjacent surfaces in a model have the same texture it can be useful to show black lines around the edge of surfaces to help distinguish between the different surfaces. You can achieve this by checking one or both of the Show external surface edges and Show internal surface edges checkboxes in the Display options panel in the bottom left of the screen. These options are described in more detail below.
When viewing the model from outside the Show external surface edges, when checked, helps ensure that all external block edge surfaces are clearly delineated. The screenshots below illustrate the effect of changing this setting.
Show external surface edges: Off
Show external surface edges: On
When viewing the model from inside the Show internal surface edges, when checked, helps ensure that all zone internal surfaces are clearly delineated. The screenshots below illustrate the effect of changing this setting.
Show internal surface edges: Off
Show internal surface edges: On
Note: When a model includes external surfaces with zero thickness surfaces, it can be better to uncheck this option when viewing from the outside to avoid any lines from internal surfaces such as partitions bleeding through to the outside. See screenshots below.
Show internal surface edges: Off
Show internal surface edges: On