Formal Aspects

A moving plane, moving in a direction other than its own intrinsic direction gives rise to a volume.

We identify a volume because of its 3rd dimension of depth and the fact that it occupies space.

Volumes have 3 dimensions.
For example, a rectangular prism has length, breadth and height.

A 3 dimensional volume is perceived in a closed or almost closed plane.

Planes that are close to each other with a common directional relationship are perceived as a volume.

Volumetric forms can be represented by means of points, lines or by means of outlines.

The perception of depth or volumetric space is created by using textures, shadows, changing colour values and the use of perspective.

Semantic Aspects

Volumes are 3 dimensional in nature and denote volumetric spaces.
In 2 dimensional representation of volumes, the perception of space and depth is illusory. Volumetric depictions in 2 dimensions (2D) are closest to how those objects would be perceived as in 3 dimensions (3D).

Practical Aspects

We are able to represent 3 dimensional volumetric objects as representations on a 2 dimensional surface. Examples of these are illustrations on paper, displays on monitors, images on movie screens, etc.