## Jul 3, 2010

### Basics of Drawing Form - Elements of Light and Form

There are a few things to consider as you set out to draw realistically. Drawing realistic form begins with the understanding of how we visually perceive light and shadow and how these two relate together to  give us the sense of  three dimensional form. There are some basic principles you can use as a guide finding form using the information from the way light interacts with the objects it comes in contact with.

It is through light and shadow that we see form. We visually use the information created from the interplay of light and shadow to understand the shape, size, and mass of an object. This is because light behaves consistently and this consistency is what gives us a frame work to to interpret three dimensional form. If you understand how the light behaves then drawing a realistic object becomes easier.

Light Follows a Path
Light is directional and it moves in a straight path emanating away from a point of origin.  The light will follow this path until something blocks it form continuing on its course. The objects that block the light will absorb  and reflect it, changing the direction of the path the light is traveling. This is what creates shadow. The space behind the object falls into shadow as the light is no longer able to continue beyond the surface in blacking the light path. That is the basis of the elements I describe below. Complexity of what is happening can scale up depending on the variables of lighting and surfaces involved but the basic principles will always apply.

When the surface of an object blocks light from going any further it creates two types of shadows, form shadow and cast shadow.

The parts of the object that are behind that obstructing surface are now in shadow. This is what we call the form shadow. Looking at the example of the sphere below you can see that as the surface of the edge bends away from the light it is now in an area where the light can not reach it.

The other shadow type with is one that is created when the surface of the object blocking the light creates a shadow on the surface area behind it. This is the cast shadow. In the example below the sphere casts a shadow onto the area of ground behind where the sphere rests.

Light Side
Looking at the light side of the form, we can see that the light is strongest or brightest on the area of the surface that is closest to the light source and gradually weakens in strength as the surface moves away from that source. The brightest part of the surface is called the highlight.  The darkest part of the surface is called the middle tone area. This is the area of the surface that is furthest from the light source while remaining in the light side of the object.