It's a condition in which people see white or black dots in parts or the whole of their visual fields.
Shading will make parts that appear farther away DARKER.
For any art work, the parts that are nearer on the artwork will appear clear while the parts that are farther away will appear faint and light. The parts that are farther away can be shaded to make them them appear darker instead of faint.
The artworks from Africa, China, and the Islamic world influence artists and patrons of the Renaissance Europe in a way that u<span>ntil European artists figured out the secret to making Chinese porcelain, they used the Islamic technique of adding white glaze over clay and adding decoration. Hope this helps.</span>
