Understanding the difference between two and three dimensions, or 2D versus 3D, can help you make many decisions in the process of creating a design. For example, if someone assigns you the task of creating a model house you can view from all sides, your understanding of 2D and 3D will quickly indicate that this is a 3D project. After recognizing this fact, you can create a physical model of the house or a virtual one using modeling software.
The term “2D,” or two dimensional, is a term designers and others apply to objects that have only two of the following three spatial components: length, width, and depth. “2D” refers to things that exist on a single plane, including graphics, both printed and digital. By contrast, “3D” refers to objects with length, width and height. A shoebox is an example of a 3D object.
2D Software Design
Software programs enabling you to create 2D designs include the popular applications Photoshop, Microsoft Paint, and Corel Painter. Though Painter and Photoshop have some 3D design factions, most of their functions create 2D graphics. You can classify these graphics into two broad categories: vector-based graphics and raster-based graphics.
Vector-based graphics are those 2D or 3D graphics you can scale to any size without losing image quality. Some design programs, including GIMP and Photoshop, call these graphics “paths,” and let you create these items with a “Pen” tool, in contrast to the raster-based “Pencil” and “Paintbrush” tools. What makes vector graphics possible is a data structure and accompanying algorithms that treat graphics not as a collection of points, but as a set of instructions for creating graphics. For example, you could relate the vector representation of a line with the simplified instruction, “Move three units to the left and five units up from the line’s start point to locate the end point.”
Most of the digital graphics you see on the Web are raster based, which you can verify by running your browser’s “Zoom” tool to maximum magnification. When you do so, you’ll see the individual pixels — picture elements — of graphics. The file structure of all raster graphics stores data that tells whatever program will display these graphics exactly what will appear in each pixel. For example, you could simplify the structure of a raster graphic of a two-pixel line to the following description: “the pixel location one unit up and one unit left from the bottom right portion of the screen will have the color blue. The pixel two units up and two left from screen bottom right will also be blue.”
3D Design Programs
In contrast to 2D design programs, 3D design programs let you define geometry that has length, width and height. These programs typically have simple forms with these dimensions predefined, such as cubes, cylinders, cones and spheres. You can use these basic elements to assemble more complex forms; for example, stacking a cone atop a cylinder to form a house lamp.
Unless you’re using computer software, creating a realistic illusion of 3D on a 2D surface requires you to understand natural phenomena like lighting and linear and atmospheric perspective. For example, to render even a simple scene with a sphere resting on a tabletop in full sunlight involves considering the sun’s position relative to the sphere, the viewpoint from which you see the sphere and how sunlight projects onto the sphere’s surface. Acquiring manual skills that address these factors typically takes extensive training. In contrast, manually creating purely 2D designs that don’t need to realistically communicate three spatial dimensions requires only that you produce marks on a surface, such as applying ink to paper.