Simulating Soft-boxes with UberArea Lights
I have some experience in photography and I know that studio photographers usually use soft-boxes or umbrellas for portrait lighting. They give soft light without harsh shadows that still looks very 3 dimensional and is flattering for portraits.
I found commercial products that added mesh lights that would simulate soft-boxes, like for example http://www.daz3d.com/shop/inaneglorys-photo-studio-3
That product looks very nice with lights to simulate beauty dishes as well as soft-boxes, but then I discovered that Daz Studio includes an UberArea light. There are presets to add area lights of various shapes, the plane and the disc being most useful for simulating a soft box. There has been a lot of discussion about portrait lighting, for example here http://www.daz3d.com/forums/discussion/1201/, but I could not find any reference to using UberArea lights to get soft-box like lighting.
Now the UberArea lights are a little weird. They are actually light emitting shaders on a surface, so you have to control them from the surface tab rather than as a light. There is some documentation on them here: http://www.omnifreaker.com/index.php?title=UberAreaLight
I decided to try to test this with a simple portrait lighting setup. The images below show the resulting render and a setup picture to show you how the area lights were placed. In studio lighting you usually place the lights 3-6 ft from the subject. You want the soft-box to look large to the model. If you place the soft-box far away, you will get hard lighting (sharply defined shadows).
For this picture I have a primitive plane set vertically well behind the model as a backdrop. The primitive plane is grey and is emitting ambient light so I don't need to light it. There is a light blue spot light near the back drop plane that is illuminating the light blue around the models head. The key light is camera left. I scaled this UberArea plane a little larger and the intensity is about 2x the intensity of the fill light which is camera right.. I used the UberArea light fall off feature so that the UberaArea lights do not illuminate the background. You can see the range of the UberArea light illumination on the black ground plane in the setup picture.
With the UberArea lights the "Samples" parameter controls the quality. The default value of 8 usually gives you noisy renders. The render below was done with samples set to 32 and the shading rate set to 0.2. It still may have some noise in the shadows. Render time was about 24 mins for 1600x1200.
I am pretty happy with the lighting and 3 dimensionality of this image. I'm surprised there has not been much discussion of this kind of lighting.