Soft Shadows: Area Lights

Up to now the lights have only been represented by a single, infinitesimally smally point. This doesn't accurately model light in the real world which comes from an object have volume. Look at a light bulb, it takes up some amount of space. The side affect of have a point light is that all the shadows are really sharp, they have very defined edges. While the edges of shadows cast by lights with volume or area have soft edges. Here is a picture of the soft edges cast in real life:

(Image courtesy of Shadow Rendering Home Page at Lund University @

Here is a series of images using area lights:

3x3 Samples

16x16 Samples

32x32 Samples