Page 116 - DCAP504_Computer Graphics

Unit 8: 3-D in Computer Graphics

The figure 8.2 shows a single curve being duplicated and placed as a set to form a surface.

Figure 8.2 : A Surface as a Family of Curves

If the curve is denoted by P (u), its duplicates can be denoted by P i (u), i being the integer index. The
integer index i can be replaced by ‘w’ for each curve. Here, w is the real index. The solid surface will
then be denoted by P w (u) here, u moves with the curve in small steps.
Polygon Surfaces

Also referred to as “standard graphics object”, the set of polygons (where, a polygon is a plane figure
bounded by a closed path) surfaces are the most commonly used 3-D graphics object representation.
The graphics system stores all the descriptions of object as set of polygon surfaces. It helps in
simplifying and speeding up the surface rendering and display of objects. A polygon representation
defines the surface features of the polyhedron object in a very accurate manner. Other than polygon
surface many packages also allow objects to be described with spline surfaces that are converted into
polygon representations.
Polygon Mesh
The polygon mesh representation is common in designing and solid modeling applications. The mesh
outline for the surface can be displayed quickly to give an indication of the structure of the surface. To
reduce the display of polygon edge boundaries on the surfaces, the realistic renderings are created. It is
done by interpolating shading patterns across the surfaces.

Mesh outline – It is a data structure used as a modeling method in the field of computer
graphics. An example of mesh outline image is as shown in figure 8.3.

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