This week I had a quick look at painting and drawing shine on objects. Last week’s “Coastal Shiner” painting picked up some shine the simple way, by just drawing exactly what is there. But it got me thinking about the mechanics of shine and reflection and wondering what rules make the patterns of light that I see in glossy objects. The way light reflects from shiny, wet objects is so fascinating but I only know the basics of how any of this works. I can feel the pattern behind the reality of what I see but find it very hard to formalise it into workable rules for painting.
I began with some basic sketches in my sketchbook…
I was playing around with how reflections sometimes show some of the local colour (or in the case of pencil sketches local tone). I found it very hard to get these sketches to read as if the two animals are wet, although the frog’s eye works to some extent.
A deep glossy shine is basically a reflection so it very much depends on the surroundings of the object. In the right light a reflective surface can look absolutely marvellous. But I wanted to know how to simplify this effect we see in nature so as to capture it in a painting in it’s simplest form. I played around with some gouache and watercolour paint on regular copy paper to see if I could find some basic rules. Here’s one of these trials…
It’s more than just the highlights – there are colour reflections between coloured objects and lower light reflections too.
So, my first step was to simplify all of this down to low light reflections and high light reflections and had a go at painting a beautiful little creature called the Spotted Salamander (Ambystoma maculatum).
I painted his body black and then added some grey highlights and some white highlights like this…
It’s not quite there but does read as a little bit shiny (if you squint a bit!)
Then I decided to paint some wet rocks in a stream. I tried to abstract things a little here to see if the basic reflection rules I’d made would go that far…
Again it reads as water but isn’t quite there yet.
I decided that this is something I am going to have to study for a while to really understand.
After reading around I found out that modelling light on objects is called an Illumination Model. In fact there are a number of different models to chose from. The more advanced the model, the more factors are taken into account and the more accurate the surface rendering is when compared to real life. This field of study began with the study of optics during the enlightenment and continues today with the huge advances in computer generated images.
For example a very basic model is called the Lambert Model which was figured out in the 18th Century CE. In this model all surfaces are uniformly matte and reflect light to the viewer according to a simple geometric law (the cosine law). It sounds complicated but really it just means that if an object is illuminated by strong directional light (like light from the sun) then the intensity of the light reflected from it varies with the angle of the object surface to the light. If the surface is perpendicular to the light source then the intensity is maximum. If it’s at an angle it’s less and the steeper the angle the less light gets reflected. This model gives us a basic understanding of illumination but is very far from being accurate.
A more accurate model is the Phong Model, from 1975, which combines three types of lighting effects…
- Ambient light – caused by light bouncing around a volume randomly in an atmosphere. This light is low level but the same everywhere. (Interestingly, this lighting is almost completely absent in space which is why spacecraft look very different on earth compared to when they are out of our atmosphere.)
- Then there is diffuse lighting which is similar to Lambertian lighting and illuminates an object at each point according to it’s surface angle to the directional light source.
- Finally there are specular reflections. These are mirror like reflections of a light source on the surface of an object. In Phong’s model these are white highlights but in more advanced models you can adjust the shininess of an object to get more or less specular reflection from tiny white highlights to a full mirrored surface, like chrome.
Anyway, I’m going to read into this a bit more to try to make an illumination map in my mind for my painting. Only time will tell if this helps at all!