Research on Basic shapes and fundamental forms

Light and shadow visually defines objects, and artists use values, the different shades of grey between white and black, to translate the light and shadow they see into shading, thus creating the illusion of third dimension. This can be achieved using techniques such as hatching and crosshatching to create shading.

Form shadow and cast shadow

Lights indicate an object’s shape and shadows define an object’s volume.

Form shadow appears on an object that receives little or no light, and the maximum intensity of the shadow is the boundary between the illuminated part of the object and its shadowed part.

Cast shadow shows the relationship between the object and the environment, and indicates the position of the light source. Cast shadow can profoundly alter the shape of the body that produced it.

Reference:

Giovanni Civardi, 2013, Drawing a complete guid, China, Search Press