Definition of "shadeable"

The draughtsman could not have held the sheet with the apse at the tip, for then, instead of shading away from the edge, most of his hatched lines would begin in the uncharted middle ground of a shadeable area, to strike against the contour; […]

1960, Leo Steinberg, San Carlo Alle Quattro Fontane: A Study in Multiple Form and Architectural Symbolism

This might seem like a special case, but everything in the model should have been created with an eye to making it easily shadeable. Often this is expressed through the naming and grouping of components that make up the model.

2003, Mark Adams, Max Sims, Erick Miller, Inside Maya 5, volume 1, page 222