Use the Rendering modes tool to change the way objects (excluding humans) are displayed on the scene.
To change the display mode, press the 
button and select one of the following options in the menu that opens:
- Fill and Lines - this will display the object using solid color fill and lines;
- Lines Only - this will display the object using lines;
- Fill Only - this will display the object objects using solid color fill.
You can change the thickness of the lines used to display the objects in Fill and Lines and Lines Only modes in the application settings. For more information, see General Settings.