Realism as a topic for artists often inspires the question: “Why bother, when we could just take a photograph?” Well, personally I appreciate art from a diverse set of genres, many of which have little to do with realism. However “suspension of disbelief” is a concept I strive for in my own work. So for me, those realistic elements are vital.
When I watch a movie, I love it when a special effect is good enough to seem plausible. Moreover, I like knowing that the potential for creating something just as convincing, sits waiting in my PC. To that end Daz Studio is an excellent free way to try your hand at 3D rendering.
For many years 3Delight was the only renderer available for Daz Studio. But with the recent arrival of alternative renderers like Lux, Octane, and now Iray, clearly more realism is in demand. What you may not know is that 3Delight possesses hidden power for creating more realistic renders. You just need to know how to take advantage of it.
So in this article, I’m going to focus on improving the look of human skin by using Gamma Correction. Bear in mind though, this really applies to just about any surface in your scene.
Note: This post is essentially a repeat of my original post in the forums at Daz3d.com. Sometimes Forum posts end up MIA, when Daz makes updates to their website. So I want to be sure everyone continues to have access to this information.
One important element of this hidden power is Linear Workflow, otherwise known as Gamma Correction. For some, Gamma Correction may be old news. After all, it was 2008 when Baggisbill compelled Poser users to start using GC in the forums at Renderosity and RuntimeDNA. In fact it’s origins go back further. I was able to find some documentation on the subject from circa 2001. Today the benefits of Gamma Correction in 3D rendering are as important as ever. Yet, it remains widely misunderstood and frequently discarded, even by experienced users and major industry professionals.
There are lots of reputable sources touting the importance of Gamma Correction in 3D rendering. And there are several decent explanations of how it works, though many are highly technical. Here are a few good ones:
Anyway, since the technical details have been well covered elsewhere, I’d like to take a less technical approach. I’ll try to explain Gamma correction in common sense terms. I’ll show exactly how to make use of two Gamma Correction methods in DAZ Studio with 3Delight:
The three most common tell-tail signs of a render without Gamma Correction are:1). Shadows that are entirely too dark (black).2). Exaggerated specular burn out (a shiny spot that is too bright and often too large).3). Color shift (a color you didn’t intend to have in the scene).
If you’ve ever worked with traditional media paints, or spent time studying color photographs and the world around you, then you may have already noticed something wrong with a lot of 3D renders. Specifically, I’m referring to the exaggerated contrast you often see, where shadows are pitch black and void of detail. Painters learn early on that you generally want to describe the shadowed part of a person or object with a darker version of the surface’s basic color, rather than black. So with a blue ball, for instance, you mix a portion of paint that is darker blue and often even more saturated in color, but rarely ever true black. Then you might use a lighter color blue for the brighter parts, and then sparingly a bit of white for the most light reflective parts.
You can bring more of these transitional colors into the mix and utilize different methods of blending. But basically, what you would do to visually evaluate what looks right, is what Linear Workflow is arriving at scientifically. It’s a better way to mix your pixel paint. In any case, a side by side comparison is probably the best way to show the benefits:
These days in DAZ Studio, since Subsurface Scattering based skin shaders are the standard, the skin may appear “waxy”, because too much SSS is being used. Without Gamma Correction it’s difficult to light human skin properly. To compensate, Daz Original characters use SSS partially for it’s primary purpose – simulating the light phenomena of translucent surfaces, and partly to make up for the lack of Gamma Correction. Therefore, when you use Gamma Correction, you can reduce SSS to physically correct levels. Often, setting SSS to half of what it was without Gamma correction is sufficient.
Using one of these two methods of Linear Workflow, we basically apply Anti-Gamma Correction to all color inputs. That way, they can be mixed with light (black to white grayscale) properly. Also they won’t be washed out when we apply Gamma Correction to everything at the end. The result is more color and detail in shadows as well as the brightest parts of our image. We also get colors that are truer to our inputs. For instance, in Figure B above, the prominent aquamarine specular halo (default) is almost non-existent in the Gamma Correction render.
Now that we’re using the correct amount of SSS for our translucent surfaces, we can make some other changes too. Don’t use SSS at all for opaque surfaces because it doesn’t exist that way in the real world. Once GC is doing it’s job, you won’t see a need for SSS in such surfaces. You may also discover that scenes you setup with Gamma Correction off are now too bright. But be aware that Gamma Correction renders will perform better whether your scenes are bright or dark. You will still be able to get dark shadows and saturated colors when you need them. You just need to reduce your light intensity, if you want to match previous scene values. Many consider reducing by one third to be a good approximation.
Many of the tricks and advanced techniques we used to light our scene without Gamma Correction become less necessary. In some cases, we don’t need to use them at all. But maybe this is enough to chew on for the moment. I hope this helps you get more realism out of your renders!