Basics of 3D display objects

The main difference between a two-dimensional (2D) object and a three-dimensional (3D) object projected on a two-dimensional screen is the addition of a third dimension to the object. The third dimension allows the object to move toward and away from viewpoint of the user.

When you explicitly set the z property of a display object to a numeric value, the object automatically creates a 3D transformation matrix. You can alter this matrix to modify the 3D transformation settings of that object.

In addition, 3D rotation differs from 2D rotation. In 2D the axis of rotation is always perpendicular to the x/y plane - in other words, on the z-axis. In 3D the axis of rotation can be around any of the x, y, or z axes. Setting the rotation and scaling properties of a display object enable it to move in 3D space.

Important concepts and terms

The following reference list contains important terms that you will encounter when programming 3-dimensional graphics:

Perspective
In a 2D plane, representation of parallel lines as converging on a vanishing point to give the illusion of depth and distance.

Projection
The production of a 2D image of a higher-dimensional object; 3D projection maps 3D points to a 2D plane.

Rotation
Changing the orientation (and often the position) of an object by moving every point included in the object in a circular motion.

Transformation
Altering 3D points or sets of points by translation, rotation, scale, skew, or a combination of these actions.

Translation
Changing the position of an object by moving every point included in the object by the same amount in the same direction.

Vanishing point
Point at which receding parallel lines seem to meet when represented in linear perspective.

Vector
A 3D vector represents a point or a location in the three-dimensional space using the Cartesian coordinates x, y, and z.

Vertex
A corner point.

Textured mesh
Any point defining an object in 3D space.

UV mapping
A way to apply a texture or bitmap to a 3D surface. UV mapping assigns values to coordinates on an image as percentages of the horizontal (U) axis and vertical (V) axis.

T value
The scaling factor for determining the size of a 3D object as the object moves toward, or away from, the current point of view.

Culling
Rendering, or not, surfaces with specific winding. Using culling you can hide surfaces that are not visible to the current point of view.