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Concepts

This is a relatively comprehensive list of the important paradigms of digital art. Once completing revision of this page, you should consider reviewing the geometry, trigonometry and physics section if you are unfamiliar with those areas from past study. A guide for calculus has been included for completeness. Then review the each guide page down the list. Once you have completed the entire guide, you should be significantly more capable with digital art, optionally bolstered with a firmer understanding of mathematics and phenomena.

3D objects are composed of vertices/points, edges/lines, and faces/polygons/ngons/quads/tris.

Flat Object

a flat image of a vertex, edge, and face

3D Object

an image of a 3d object with a vertex, edge, and face

3D objects transformed (moved, rotated or scaled) in 3d space according to the X, Y and Z axes. The transform handle can be manipulated to cause the movement:

Blender Object Transform

local transform and axes shown, z points up (in Maya, y points up)

Aspect ratios are image proportions definitions, while pixel aspect ratios are re-scaling instructions, usually left at square pixels (1) for computers:

4:3 aspect

standard definition (SD) aspect ratio

16:9 aspect

high definition (HD) aspect ratio

Pixel Aspect Ratio

common pixel aspect ratios

Pixel Aspect Rescaling

example of pixel aspect re-scaling

In 2d art, there are two types of images, a raster image (PNG/JPG/TGA/GIF etc.) and a vector image (SVG/EPS/AI).

Big Raster

exaggeration of enlarged raster image - it loses quality when zooming

Vector Comparison

a vector image compared to a raster scale - vector preserves quality but it is hard to maintain fine details in vector images

There are two primary object types in most 3d applications: polygons and NURBS. NURBS are mathematically defined surfaces, while polygons are defined by vertices. NURBS curves exist in Adobe Illustrator, while the polygon concept is similar to the rasterization in Adobe Photoshop. It is usually better to use polygonal models for finer control, while NURBS usually gives a pleasing, quick result. When rendering (outputting a file), the NURBS object must also be tesselated, sometimes losing the smooth appearance unless taking extra render time.

Polygon and NURBS

polygonal sphere on the left, NURBS sphere on the right

In order to approximate values between key points, interpolation is used in animation between keyframes, 3d curves and paths, and attribute properties (for a color gradient or opacity curve relative to distance, for example). In addition to the most common types shown below (linear and spline), others include step and bezier. For more information on the bezier system, please see the photoshop pen tutorial.

Linear Interpolation

linear

Spline Interpolation

spline

When defining curves, the key points are usually specified with tangents, especially in the case of a bezier anchor point (unless broken).

Tangent

tangents just touch a curve's immediate area at the anchor point, but may intersect at farther areas

The faces of 3d objects must be marked with a normal configuration that determines the direction of the face to allow for proper lighting and texture placement. In general, the normals of a polygon all face outwards or inwards, and in similar directions for nearby faces.

Polygon Normals

faces have two normals and only one marked normal

Surface Normals

a normal of a face points directly outwards (or inwards) from the point

Multiple Surface Normals

many surface normals exist, two per face (outward normals shown here)