reference by Monika Zagrobelna
What are materials and textures? How can we see transparent things? What makes a scene something more than a set of objects? How do you mix reflected colors? Learn tricks that will bring life to your realistic paintings!
This is the the last part of our mini series on color and light. In the first tutorial welearned how to see light and shadow, and in the second one, the principles of color. Today we’re going to learn some advanced tricks that will give your artwork a real spark. The key word here is variety, in color and form. If sometimes the things you draw look like plastic figurines, this tutorial should help you a lot!
Most of the problems with painting colors lies in the depiction of surfaces. The surface structure influences our perception of color and brightness, and there are a lot of issues you need to take control of. When ignored, it can make for a dull, “plastic” scene. Plastic is the default material of every beginner’s drawings—let’s move past that.
Specular and Diffuse Reflection
In the previous tutorial I mentioned glossiness, but I didn’t emphasize how important it is. In general, there are two kinds of color-making reflections: diffuse, and specular. Usually they’re mixed together, and the proportion between them creates the overall reflection we perceive. So we can see matte, gloss, matte shine and all the stages in between.
As we noticed before, specular reflection is made by a ray reflected perfectly by the surface straight to our eyes. The more specular the surface, the clearer image of the light source appears on it. The less specular it is, the fuzzier the image, until it eventually becomes just a blurry spot of a diffuse reflection shifted to the light source’s color. The shiny layer may be a property of the material, or just an effect added by water.
It’s safe to treat every material as partially specular. Even a rubber ball or a plush has a little bit of shine. Using various specularity levels for the materials on your scene is very important for diversity. Shine is so powerful that it’s tempting to use it everywhere, but flooding all the scene with oil isn’t really the way to an attractive artwork.
A clear specular reflection doesn’t always have the color of the light source. It works like this only if the “specular layer” (that’s a simplification, but there’s no need to go into technical details) reflects all the colors. If it doesn’t, we get a red ball with clear green opalescence. It’s a nice effect for gemstones, expensive fabrics, feathers (for example, ravens are black with blue tint) and the carapaces of beetles (blue tint on a green body).
The level of specularity should also be used to show how rough or polished the material is. A rough material after careful polishing will reflect a lot of light, so you should use a different specularity for an old wooden table and a polished wooden bowl—although they are made of the same material, their tooling made the difference.
Texture isn’t only about shape of a surface and the way it should be drawn, but also about the reflective properties of the material. Every surface is made of tiny objects, and they all react to the light source too—they cast their tiny shadows and have their little highlights. That’s why simply pasting a half-transparent textured photo over the top of a drawn material doesn’t always make it look “right”. The finer the texture, the less this effect occurs, but you need to be careful with bigger ones, like scales or bark. Also, every rough texture drastically decreases overall specularity of the surface!
The perceived specularity of a surface depends on the angle of view. The sharper the angle, the clearer the reflection. This effect is very helpful in finding a perfect place to define glossiness of our material, and it also tells us when to treat water or glass as a transparent material, and when it should work like perfect mirror. You can observe this phenomenon on wet floor—the lower you keep your head, the clearer the reflection.
Transparency is troublesome, because its intuitive definition is almost impossible to be conveyed into drawing. A simple change in the opacity of an object makes it look like a ghost, not like a glass. That’s because our casual definition of “transparency” simplifies the issue.
Let’s see how it works. Colored glass is easy to explain: for example, red glass absorbs all the colors, and only red passes through. Putting it simply, it works like a color filter.
Intuitively, a fully transparent material lets all the rays through, without any absorption or reflection. But if the rays didn’t interact with the material in any way, how would we be able to see the material?
If you read the previous paragraphs carefully, you should guess the answer—only a 100% matte material reflects nothing. So even our pure glass reflects a bit of specular reflection, showing us the surface.
An interesting fact: specular reflection is what turns a lake of transparent water into a mirror!
But how do transparent objects like water drops or glass cast shadow? This is based on refraction, the bending of the rays when they pass between two media. Including this phenomenon in your painting gives a transparent object a sense of volume—this is the difference between a solid glass ball and a bubble.
You should remember this scheme from physics classes. The only thing we need to remember here is that the thicker the material, the more likely the rays will be disturbed.
The situation gets even more interesting when the surface is bent, creating a lens. Lenses have an amazing ability to focus or scatter rays. And when rays are focused (bent from their initial direction to one single point), areas of shadow appear. That’s how a transparent lens creates a shadow!
Every transparent object with bent surface makes a lens. Every convex lens is able to focus light to some extent. Therefore, a wine glass, a bottle of water or a drop will all cast a shadow and very bright spot (or smudge, depending on how good the lens is) of focused light. If, additionally, the lens is colored, the bright spot will be colored too.
But what does such a convex lens do? Of course, it magnifies! That’s the most important thing you need to paint realistic transparent, solid materials. Continue reading