T - Touch Point.

The point under the form, past the profile edge, where the form is actually resting on the surface.

Sketch an ellipse through the sphere, aligned perpendicular to the Light Angle.

For Parallel Shadows, use a relatively flat ellipse and use the lower arc to define the core shade/shadow.

For Positive Light Shadows, the shadow is coming toward us, then use the upper arc for the core shad.

For Negative Light Shadows, the shadow is moving away from us, then use the lower arc, and a more open/round ellipse if necessary.

Learn more about
Shadow Casting Here

A - Apex

The point at the high point of the sphere, like the North Pole.

LA - Light Angle. The angle at which your light source is coming from.

Core Shade or Core Shadow.

GA - Ground Angle

Vertical lines and edges translate horizontally across the ground, coming from the light source direction.

TUTORIALS & HOW-TO GUIDES

A helmet can be easily approached from thinking of a sphere
or egg-like form.

Remember there's
no such thing as Black
(or white), there are only
values in a dark (or light)
spectrum. There must always be
a Core Shade Value, Highlights, and even
Bounced Light or Reflected Light on the surface
area rolling down under the form. This light is
reflected light from the table or base plane.

One of the more common places to apply this logic is in rendering tires that have a very high dome profile, such as a motorcycle slick street tire.

This form study below is based on the Torus, the donut-like geometry.

CSULB |  COTA  |  DEPARTMENT OF DESIGN  |  BIO

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