Shadows without lights
Lighting and shadows can each be disabled independently. You can keep shadows visible, even when lighting is disabled, allowing you to keep the original unshaded look of the scene. Turning off lighting also changes the way shadows are rendered.
When shading (the visible effect of lighting) is disabled, shadows behave differently. Rather than being multiplied with the object upon which they are cast, the shadow’s color and opacity are controlled only by the Shadows settings in the Light Inspector.
This allows you to create shadows of any color or opacity, from traditional dark shadows to brightly colored or even white shadows.
You can disable shading globally in the View pulldown menu (choose View > Render Options > Lighting to remove the checkmark from the menu item) or in the Render pop-up menu above the Canvas (choose Lighting to remove the checkmark from the menu item). You can also disable shading for a specific layer by setting the Shading parameter in the Properties Inspector to Off.
With spot lights, enabling Shadows but disabling shading can create a seemingly strange result where the shadow is suddenly cut off because it has exceeded the scope of the light cone. Because the shading effect of the light cone is turned off, the shadow edge looks unnatural.
To correct such an occurrence, increase the Cone Angle in the Light Inspector.