2D and 3D Graphics
For many years CAD was carried out using computer terminals connected to central computers, where the central computer resource was often shared between several terminals. Now each user terminal is a computer in its own right. This is adopted in personal computers and high-performance engineering workstation.
Workstations may be linked together to allow the exchange of data and programs and the sharing of peripherals through networks.
Two-dimensional computer graphics
The central aim of computer graphics in CAD is to perform the transformation from design model to display in an efficient manner. The essential steps of the process are to Convert the geometric representation of the model to a form that may be manipulated by the graphics routines. For the most part, this means converting to lines often termed vectors. Map, or transform, the lines from the model coordinate system to the screen coordinate system. Select those lines that are within the part of the model that it is wished to display- this is known as clipping step. Instruct the device to draw the vectors.
The sequence of operations in generating an image in two-dimensional graphics.
Three-dimensional computer graphics
The elements of three-dimensional computer graphics are broadly the same as those for two-dimensional graphics: the model is converted to a simple graphical representation such as a collection of vectors, these are then clipped to the window boundary, transformed to screen coordinates and displayed in a viewport on the screen.