Area lights are a special kind of point light and spotlight. The rays emanate from a geometric area instead of a single point. This is useful for creating soft shadows with both an umbra (the full shadow where an object blocks all rays from the light) and a penumbra (the partial shadow where an object blocks some of the rays).
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| The chess piece on the left is lit by a standard point source light producing sharp shadow edges. The same piece on the right is illuminated by an area light which creates blurred shadows. |
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The shadow's relative softness (the relation between the umbra and penumbra) is affected by the shape and size of the light's geometry. You can choose from a variety of geometry and transform the geometry area as you wish.
To determine the amount of illumination on a surface, a sample of points is distributed evenly over the area light geometry. Rays are cast from each sample point; all, some, or none of the rays may be blocked by an object. This creates a smoothly graded penumbra.
For complete information about working with area lights, see Creating Area Lights and Transforming Area Lights [Direct Illumination].
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