Photographers do this in the studio by bouncing light off white surfaces or by shining the light through big diffusion screens made from transparent white material.
The best form of diffusion I've found for a natural daylight studio is the sheet foam that many appliances come wrapped in. I use it to cover the windows when I set up a daylight studio in my clients homes, it creates the softest light but doesn't alter the intensity or brightness of the light. It also serves to simplify reflections in shiny surfaces like the eyes.
I'm about to try a roll of frost cloth on a newborn shoot tomorrow, I'll share the results soon.