Simon Frankau's blog
Ray-tracing fun: Soft shadows
As a follow-up to depth of field, I've now implemented soft shadows. I used two lights, one large, dim area light above to soften most of the shadow (getting right under the sphere on all sides), and a smaller light to the side which changes colour across it, to give the image some interest in the colour. I'm not sure the colour on the shadow works quite right, but I think it gives some nice warmth to the highlight in what would otherwise be a monochromatic image.
Posted 2014-12-22.