Texturing Realistic Skin - Tips and Techniques for Painting Believable Skin
Creating realistic skin textures is something that will most likely need to be accomplished at some point in your CG projects. Whether it's for a human character, an animal or some type of mythical creature there are some basic techniques and workflows that can be applied for just about any character to help establish realistic skin textures. An artist's first instinct may be to simply take photographic reference and project it onto the 3D model, while this method can work it's not always the best route to take.
Having the skill and knowledge to be able to hand paint your own skin textures will allow you to create realistic skin for any project whether it's for a human character or even a tree frog. This article will cover some of the main techniques that go into texturing realistic skin so you can start implementing them into your own projects.
This may sound contradictory to what was mentioned previously about not taking photos of skin. But that doesn't mean you can't study reference to get an idea of what goes into skin, and why it's so unique. Skin textures are one of those things that a viewer can quickly see if it's believable or not, they may not know on a technical level what makes it feel "fake" but they will know when something feels off.
Find reference online of different skin and study it. How do the veins flow along the hand? How prominent are the specular highlights and how do the small cracks and wrinkles form on different areas of the skin? Studying these different things can help you establish realistic textures for your model.
Gathering reference is not only important for creating human skin but you can also get reference for different creatures, whether it's an animal or even a mythical creature. Don't be afraid to get creative on the type of reference you use. For instance, you may have a Goblin creature model that obviously isn't grounded in realism, but you can still get skin texture ideas from something like a baby pig or a hairless cat. Some of the best reference is in the most unlikely places.
Create a Bump Map
Almost all skin has a certain level of bump to it. If you were to look closely at your own skin, you'd see it's not perfectly flat. Painting in pores and different bumps can really help push the realism of the model. Your first thought may be to establish the diffuse color, but first creating the small details is usually best to do first because these things can change the look of the diffuse.
It's also important that you don't overdo the bump for your texture. The bumps and pores on skin are typically very subtle so make sure you're creating the bump with some caution. It can be very easy to overdo a bump map and creating a skin texture that is too bumpy can create some very unrealistic results.
Create Small Imperfections
Along with creating the bump for your skin textures it's also a great idea to add in small little imperfections like cracks and scratches. If you look closely at the top of your hand you'll be able to see very fine cracks that run along the surface of your hand.
Your first thought may be to sculpt this detail in a program like ZBrush or Mudbox, but you can actually get nice results from painting this detail in. It's important that you should keep the same caution you did when painting a bump map because you don't want to overdo this process. These little details should be very subtle.
Add a Subdermal Base
Creating the subdermal base for your skin is vital for establishing a very realistic look. The subdermal base are the details that lie just beneath the skin. For example, the veins and blood that gives the skin its reddish hue in certain areas. This is the meat and flesh that the skin covers up and protects. This should be painted on first before the diffuse because the diffuse color is going to cover up this subdermal layer.
Once you've established the diffuse color for your skin you can start to reveal the subdermal layer. Of course the subdermal layer should be very faint and may only be visible in certain areas on the skin but having the proper subdermal layer painted with the different vein and blood details is critical for creating a realistic skin texture and should be implemented when you're painting the skin for any character.
Skin has a certain level of shininess to it, and creating a specular map is important for giving the skin that level of sheen. Having the right level of specularity is vital for giving the illusion that it's actually skin. Without specularity it can look flat and unrealistic.
As with the bump map you don't want to overdo the specular map, if you overdo it the skin can quickly look more like plastic, so make sure you find the right balance.
Translucency is one of the key characteristics of skin. You may not know just by looking at it, but skin is actually very translucent. Of course, it's not see-through, but there are many different layers that make up someone's skin, that's why it's very easy to see veins and blood under your skin.
Creating translucency for your skin textures is one of the best ways to sell that it's actually skin. If you overlook this step, no matter how your bump map looks or how well your specular highlights are implemented if your skin texture doesn't have the right amount of translucency it won't look believable.
By making sure you incorporate some of these techniques and understanding some of the key characteristics of skin like the translucency and specular highlights you'll be sure to create believable skin textures for any project you may encounter. If you want to learn more check out Painting Realistic Skin in Mari: Hands to get an in-depth look at how to hand paint believable skin.
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