Final answer:
Artists create the illusion of 3D form in a drawing, such as a cone, by using shading to apply darker tones where light is naturally blocked. This technique simulates depth and curvature, with the placement of shadows depending on the light source's position relative to the object.
Step-by-step explanation:
To create the illusion of 3D form in a drawing of a cone, the artist manipulates light and shadow through a technique known as shading.
Shading applies darker tones to areas where light is blocked, giving the impression of depth and curvature. Just as Raphael used variations in value to convey three-dimensional forms in La Donna Velata, an artist drawing a cone would need to determine where the light source is coming from and add shadows appropriately.
The areas on the cone's surface that are farthest from the light source would be the darkest, while the areas nearest the light would remain lighter, simulating the way light falls on a three-dimensional object.
Moreover, artists like Cézanne, who was inclined towards breaking down natural forms into their geometric essentials, would conceptualize the cone by its fundamental geometric shape, enhancing its three dimensionality.
Computer-generated art also has its techniques to create 3D objects and virtual reality works, but in traditional drawing, these geometric concepts are translated onto a two-dimensional medium through skilled shading and perspective drawing.