Contact Shadows and Indirect Light

Contact Shadows and Indirect Light

For the most part, successful shading in a 2D scene relies on
getting what you can practically, and getting creative when
there are no practical shadows. There are plenty of cases
where a full cast shadow would be correct and no shadow at
all clearly looks wrong, but a simple contact shadow will at
least remove glaring contrast.
A contact shadow is a lot like a drop shadow, basically just
an offset, soft, dark copy directly behind the foreground.
A drop shadow, however, is good only for casting a shadow
onto an imaginary wall behind a logo, whereas a contact

shadow is held out to only the areas of the foreground that
have contact with the ground plane.
Figure 12.17 shows the foreground layer duplicated and
placed behind the source. A mask is drawn around the
base, and it is then offset downward. A blur is applied to
soften the transparency channel. That gives you the matte.
A shadow is not just a black overlay; it’s an area of reduced
light and therefore, color. Instead of darkening down the
matte itself to create the shadow, create an adjustment
layer just below the contact shadow layer and set an Alpha
track matte. Add a Levels (or if you prefer, Curves) effect
and adjust brightness and gamma downward to create your
shadow. Treat it like a color correction, working on separate
channels if necessary; the result is more interesting
and accurate than a pool of blackness ..
Refl ected light is another type of contact lighting that
plays a role in how things look in the real world, and thus
in your composited scenes. Most objects in the world have
diffuse surfaces that refl ect light; when the object is prominent
or colorful enough, your eye expects it to affect other
more neutral neighboring surfaces .

In 3D computer graphics this fact has been realized via
global illumination, which considers light and surface
interactions in a render. If you’re working with a computergenerated
scene, aim for a pass that includes these types
of light interactions. If you have to create the effect from
scratch, the method is similar to that of shadows or color
matching: Create a selection of the area refl ecting light,
including any needed falloff (that may be the hard part),
and use color correction tools to color match the adjacent
object refl ecting color.