Types of Light, Cast Shadows & Perspective of Shadows

Greetings, this week we will be continuing our discussion of Andrew Loomis’ book Successful Drawing, and considering types of light and how to represent shadow.

He begins by indicating that there are two main types of light. These types are

Direct light
Indirect light

Loomis emphasizes that the decision to treat a scene or subject which an artist is attempting to represent, begins with choosing one or the other of these 2 types. It is important to choose only one of these types, and to stick to it because the treatment of light in a drawing is what gives the art an impression of consistency. The absence of light could technically also be a 3rd category, but Loomis doesn’t even mention it because the drawing would be pure black. Any small amount of a subject matter, regardless of shadow depth around it, is an effect of Indirect Light treatment.

With the casting of light, comes the Cast Shadow. Cast shadows are the areas of a drawing where your subject matter interferes with the direction of light, and that interruption shows on another plane in the form of a shadow. The shadow you see of yourself on the ground on a bright day is a Cast Shadow. This is different than the type of shadow called Shading; ie. how lights and darks fall on an object, as discussed previously. Although one could consider the Shading on the dark side of the moon, to be a shadow which is cast by its lit side, such reasoning only confuses the issue. It is better to think of Cast Shadows as those shadows which an object throws onto another plane or object.

Cast Shadows: the interruption of light caused by an object, translated as darker value, appearing on a secondary object.
Shading: the translation of how light falls on a specific form, related to that form’s general shape.

When representing Cast Shadows, the artist must consider 3 factors. These factors are as follows:

position of light source
angle of light
the Vanishing Point (VP) of the shadow on the horizon.

Each of these three must be understood in order to place a Cast Shadow convincingly within the context of the scene an artist is attempting to represent. Loomis shows us how to do it. He indicates the best way to cast the shadow properly is to alter the plane of your subject matter which is facing the light to a square. Draw this square properly extending to the VP. Then, using the line the light falls at, project a central line and lines from the corners to the angle of ground you have your subject matter sitting on. This will show you how a square casts a shadow.

Example.

Here are the steps.

Contour draw your actual subject matter with light pencil. Decide where the light is hitting the object and the angle it is coming at.
Draw a line of the light direction, and approximate the “Illustrator’s Bump” (see last post) which will show at the transition from light to half tones. The line of light will bisect the Bump.
Draw a flat square shape, representing a simplification of the plane of your subject matter which is facing the light. Set the square to the VP which your actual subject matter is related to. Cast diagonals from corner to corner of your new square to reveal the centre. I do this on a separate layer to keep the original artwork clean. NB> the line of light is not related to the perspective lines. They are at separate angles.
Project the edge of the square onto the ground at the angle you imagine your subject matter to be sitting at. This angle goes to the horizon again, at a secondary point, where the VP of the shadow points.
Cast a line parallel to your light line off of the top near corner of the square. Let it cross the angle line you drew in step 4.
From the bottom near corner, send a line to the VP. Likewise do the same from the point where the top light line from step 5 bisects your ground angle. Lines to VP are pink, Light lines are green. The pink perspective lines show you the top of the projected square.
Use the points of the square to draw the other side of the projected square, bisecting the top perspective line you just drew. Aim this line to the VP of the shadow used in step 4. This line will establish the mostly hidden other side of the projected square. The yellow line represents the opposide edge of the projected square.
On another layer, draw lines from corner to corner on the projected square, and where they cross, draw a third dotted line parallel to either side. That dotted line is the centre of your projected square. These guides will help you draw the projected shadow of your original subject matter.
Using this information you worked out, go back to your original contour drawing of the shape, and add the proper modelling of form in light, as well as the Cast Shadow laying on the ground beside. Don’t forget the Illustrator’s Bump, where the shaded side meets the lit side.