What does a cross-contour line help to describe in a sculpture?

A cross-contour line is used in drawing and sculptural representation to indicate the three-dimensional form and volume of an object. These lines follow the surface contours of the subject, revealing how shapes curve and bend in space. This technique is particularly effective in helping viewers visualize the mass and volume of a sculpture, providing a sense of the object's three-dimensionality.

By utilizing cross-contour lines, artists can communicate the shape of an object more dynamically, portraying how light interacts with its surface and how the form exists in a three-dimensional context. This makes it easier for the audience to understand the physical presence of the sculpture, enhancing the perception of depth and structure.

In contrast, the other options, while relevant to different aspects of art, do not specifically capture the primary function of cross-contour lines in describing sculpture. For instance, while shadow and depth may result from the interplay of light on surfaces, they are not the direct focus of cross-contour lines. Similarly, texture and patterns relate more to surface quality rather than the form itself, and color and tone pertain to the visual element of hue rather than the structural description provided by cross-con touring.