Which element often influences the perception of shape in a painting?

Light is a fundamental element that significantly influences the perception of shape in a painting. When light interacts with the surfaces of objects, it creates highlights and shadows that define the contours and dimensions, thus giving a sense of form. Artists utilize light to manipulate how shapes are perceived, employing techniques such as chiaroscuro (the treatment of light and shadow) to enhance the three-dimensionality of their subjects. The way light falls on an object can alter its visual appearance, making it appear more rounded or flat, which directly impacts the viewer's understanding of the shape depicted.

While color, size, and composition are also important elements in a painting, they play different roles in how we interpret visual information. Color can affect mood and atmosphere but is not primarily responsible for defining shape. Size can give context to an artwork but does not inherently influence the perception of shape in the same fundamental way that light does. Composition organizes visual elements within the artwork, but again, it does not specifically affect the perception of shape as directly as light does.