Modeling Form -Part One
Modeling is the act of turning form through value or line, a process which is integral to representing your impression of the scene as well as the illusion of form. Without modeling an artist ends up with a predominantly flat/2dimensional image. Thus over centuries, artists have pushed the limits of two dimensions seeking to trick the eye into believing that what is drawn on a flat surface has the added dimensions of roundness, mass, and that space and depth are also created, giving air to the scene. Although there is some crossover, there are essentially two approaches to modeling: form over value, and value over form. This the artist achieves by careful observation of light and dark/shadow and the careful and deliberate rendering/shading of these light and dark areas and all the values in between.
As its name implies, form over value modeling tends to prioritize the representation of form over that of value. The opposite is true for value over form modeling.
There are four basic laws of light upon which the form over value approach is based:
- Light travels in a straight line.
- When light strikes an object, it reflects off of it in a certain direction.
- Every object can be thought of as being made up of numerous facets or microfacets.
- As the direction of the facets on an object are tilted away from the light source, their reflected value gets darker.
The truth is without light there would be nothing to draw! This is fundamental to the artist’s understanding. Until he realizes that, he’s shooting blind. The artist therefore, if he is to improve his drawing, must learn how to see light and shadow.
Here comes the first, the most important and foundational principle of drawing: light is the only thing we can see. It’s not an object, not a color, not a perspective, not a shape. We can see only light rays, reflected from a surface, disturbed by the properties of the surface and our eyes. I have always told my students, and through demonstration that the absent of light means the absence of form, while at the same time, extremes of light on an object flattens the form and even renders form obliterated. This is why photographers are careful to reduce their use of flash when photographing subject matter with great detail or if unavoidable, use flas with a diffuser so as not to disintegrate the form. This is also the reason I do not advocate that my students draw from photos until they have a full understanding of how form in space is affected by light.
To understand how these laws apply to modeling through form over value, imagine a sphere composed of thousands of tiny facets, or planes, with a singular light source directed at it. Now imagine that the light source is projecting a column of light towards the sphere, composed of thousands of tiny beams.
Once the column of light hits the sphere, the individual beams bounce off of whatever facets they hit and those reflected beams keep on traveling, this time in a new direction. You, while viewing the scene, perceive the reflected beams as illumination.
When the direction of a beam reflects directly towards your eye, you perceive a highlight on the sphere. When the angle of a facet is tilted such that no incoming light strikes its surface, you perceive that facet as being in shadow. In-between are beams of light that hit the sphere and reflect back at various angles. These facts alone can help you model a form whether you are looking at its source or not.
Separating the zone where light hits the sphere (also called the world of light) from the zone where no light hits the sphere (also called the world of shadow) is the terminator, which is also known as the shadow line, and the bedbug line.
Form is perceived, and modeled, within the zone of light. Artists divide this zone into highlight, light, and halftone. Some further subdivide those into smaller increments. As the angle of the facets tilt away from the light source, the values we perceive them to be become darker. This is called light fall-off. It is important to know that light falloff is not linear. In other words, the value change is not in an even progression.
This drawing, by the Italian artist Michelangelo is typical of the style of figure drawing that was taught in the seventeenth and eighteenth centuries. A beautiful drawing though it is, note that each sub–form (especially in the back and arm) appears to be separately modeled. It is unlikely, that he based his modeling on the process of form over value through facets as this is a relatively recent approach. More likely is that he based his form observations on his knowledge of anatomy.
There are many ways to model via form over value: from using facets, to sections, to anatomy. Although this may prove to be a wonderful way to model a form as many artists have done over centuries (Michelangelo, Steve Huston, Burne Hogarth and others). There are simpler ways that one can arrive at a satisfactory result and one that is practiced by every famous artist.
Before you would begin to model, and perhaps before beginning the main drawing or painting itself, you would likely sketch a small value study of your subject. The purpose for doing this sketch is to acquaint you with the general direction and flow of light across the subject.
Next, on your final work surface, you would define the outline of the subject as well as the precise location of the terminator. The terminator defined the main division of light and shade so it is now time to begin modeling the forms.
Below is the approach taken by Darren Rousar- an artist who paints and draws using the Sight Size Method as exemplified by Charles Bargue, and which is currently taught by most Classical Ateliers.
Unlike the process of modeling through value over form, where you try to model the entire subject at once, when modeling through form over value you will be modeling either in strips or sections, thereby paying attention to the full detail of each section of the subject so as to express each area in its full form structure.
For the strip approach, you would first imagine the subject as a series of individual strips that follow the path that the light takes across the form. These might be strips across the entire subject or be restricted to each sub-form of it. The orientation of the strips is based upon the overall range of value on the subject, with the best choice having the largest range from dark to light. Oftentimes this results in strips which are at an angle perpendicular to the direction of the light source. You might actually indicate the edges of the strips, very lightly on your drawing, or you might simply keep them in mind as you model.
Each strip is then imagined as a series of facets, angled towards or away from the light source. You might even lightly draw the boundaries of the facets in as well.
To actually begin modeling you would choose a strip with which to start and flatly shade in the facets on the strip which are in shadow. After that you would model (shade) towards the light as evenly as possible, getting progressively lighter until you reached the light area represented on the strip. Your intent is to model to such a degree that the visual implies the tactile – it looks like how it would feel. Throughout the process you would try to think both about the turn of the form, as would a sculptor, and the flow of light through its angles of incidence and reflection. Your observations, filtered through your knowledge of light, would influence how dark or light you should shade each facet.
After the first strip is initially modeled, you would then do the next strip (or sub-form within the strip) and so on.
Once all of the strips are modeled, you would darken the shadow facets again, this time smoothly blending them into the next lighter value. Finally, you might need to lighten whatever highlight is visible in the strip.
An alternate version of form over value modeling is shown in the image above. Instead of modeling via strips, this approach uses sections of the subject. Once the shown section was fully modeled, the artist would then move onto another section of the subject.
A few things should be obvious from the preceding explanation. One is that in either case, strip or section, it is piecemeal seeing as well as modeling. Mitigating that is one reason why the aforementioned thumbnail sketch would be created. As you model, you will reference it to help you maintain the big look of light and shade. Additionally, after modeling a few strips, you would go back to the preceding strips and correct any errors and aspects which did not properly connect them with the others.
This process of modeling is also a version of window shading. Normally, window shading is done in a top-down manner. But it can be done from any direction and in strips or sections. Modeling errors inherent in the process I outlined above are corrected, hopefully, as you go over the strips for a second and third pass, as well as by continually referencing your thumbnail value sketch.
Finally, there are many artists who are being taught to model using the form over value approach, or who use it professionally. All agree that although visual perception is important when modeling through form over value, the last word on the matter is always the conceptual. Thus at times the form is exaggerated which can make the subject, even with all proportions correct, seem unrealistic.
- These distinctions should not be considered exclusive. Nonetheless, they do represent two schools of thought whose approaches to seeing, and therefore modeling, are sometimes worlds apart.
2. Most Sight-Size artists are taught to model almost entirely relative to their visual Therefore, beyond the basic concepts of light and shade, I do not normally explain the form over value approach to my beginning students. Instead, I prefer to have them learn how to see before they delve too deeply into the physics of light. - Ignorance of the concept of light and shadow is the primary cause of over-modeling (making the halftones too dark) in form over value drawings and
In the next article we will look at “The Block In”. What it is, why it is important and steps to a successful block-In.
Many thanks to Darren Rousar for his insights on drawing using Sight Size.
Mortimer McPherson
April 2019
