CG Basics - An Introduction to Computer Graphics for Artists - page 21

Table 2.4 Draw modes

Mode Result

Wireframe All geometry is drawn as lines connecting vertices

Backface culling Backwards-facing polygons are culled. All others are drawn

Hidden line Similar to backface culling, but also occludes view of overlapped

elements, such as grid

Shaded Rendered with an ambient light

Shaded with wireframe Same as shaded, with lines drawn along all edges

Ghost/X-ray Semi-transparent view of shaded geometry

Textured Assigned textures rendered in shaded mode

Scene lights Instead of using default light, scene lights are used

Textured and scene lights Assigned texture maps and scene lights are rendered

Table 2.5 Vertex notation
Line number Vertex label Vertex number X-axis Y-axis Z-axis

First V 1 1 2 3

Second V 2 2 2 1

Third V 3 3 2 2

2.4.1 Components

2.4.1.1 Vertex

A vertex is a single coordinate, or a point, in world space. It has no dimension and
very few properties by itself. To fi nd the location of a vertex, you simply need to
know how far from the global origin it is in each of the three major axes. This is just
like plotting a point in Math class, with the addition of an extra dimension to work
with, the Z-axis. There are different ways of describing vertices, but the following
table (Table 2.5 ) gives an idea how it is done. The vertices described in the table
correspond to the position of vertices in Fig. 2.15 .
The letter “V” is placed at the beginning of each line to identify the coordinate as
a vertex. Following the “V” are three numbers. These are the individual axis coor-
dinates. The space between numbers is a separator between each axis coordinate.
The horizontal order of the numbers corresponds to the order of the three global
axes: X, Y, and Z. The vertical order of the lines is the same as the vertex numbers
assigned to each set of coordinates.
The same vertices would be written something like this in an ASCII (text) fi le:

V1 2 3
V2 2 1
V3 2 2