Gradient Shaders for Skin Renders

By Yves Poissant

A few months ago, I've been working with gradients to help render skintones. Here are some very partial results. There is still some experimenting to do but the result are very interesting.

The render on the left was produced with a simple color for the skin tone. The skin tone changes in luminosity but does not change in hue as light incidence increases. The render on the right uses a gradient in combination with the Gradient shader. The gradient is designed so that the skin color shifts toward red as light incidence increase. The two renders where produced with exactly the same default 3 light choreography setup.

Those are more examples of different gradients used to render different skin tones. It can get quite wild. For example, try the Thermo gradient. But with care, it can produce quite acceptable results.

There are actually 2 types of shifts in the tonal variation. A shift toward red and a shift in saturation. The two shift are not quite in phase one from the other. So the main difficulty is to get the two shifts right. Trying to do that in Photoshop proved to be too much work. So I had to program a little application that allowed me to tweak the Hue, Saturation and Value of the gradient specification.

Note that the gradients are not used with the Toon shader but rather with the Diffuse shader plugin where I select "Gradient" from the list of shaders.

I haven't had the time to work again on those gradients