CONVEYING LIGHT
While tonal values can imply depth on aflat drawing surface, we turn to light
to more vividly describe the three-dimensional qualities of forms and spaces
in our environment. Light is the radiant energy that illuminates our world
and enables us to see three-dimensional forms in space. We do not actually
see light but rather the effects of light. The way light falls on and is
reflected from a surface creates areas of light, shade, and shadow, which
give us perceptual clues to the surface's three-dimensional qualities.
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The light-and-dark patterns we see emanate
from the interaction of light with the objects
and surfaces around us. Within these patterns
of light and dark shapes, we can recognize the
following elements:
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·
_ - - Light values occur on any surface turned
toward the light source.
Tonal values shift as a surface turns away
from the light sou rce, w interme
ith
diate
values occurring on surfaces that are tangent
to the direction of the light rays.
_______. Highlight s appear as luminous spots on
______....-----smooth surfaces that directly face or mirror
/...-----the light source.
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Shade refers to the comparatively dark values
of surfaces that are turned away from the
light source.
Shadows are t hedark values cast by an object
or part of an object upon a surface that would
otherwise be illuminated by the light source.
Areas of reflected light-light cast back
froma nearby surface-lig htenthe tonal
value of a portion of a shaded surface or a
shadow.
• T l value is the graphic equivalent of shade
ona
and shadow, and can on ly indicate light by
describing its absence.
Digital Lighting
Modeling and rendering software enable us to specify the orientation of the
sun in order to study the solar responsiveness of a design. We can also
designate the number and type of light sources to simulate the lighting
within aspace. These simulations, however, are often only approximations
of the effects of point sources and their energy distribution profiles.
Judgment of the end result, therefore, whether produced by hand or the
computer, remains the responsibility of the illustrator.
RENDERING TONAL VALUES /1 35