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Example of Wireframe Model.

4.9 SURFACE MODELS

In an attempt to solve the drawback of wireframe models, some modeling schemes add information

about the surfaces in the part. In these systems, the user enters the vertices and edges as in
wireframe models, but in an ordered manner, outlining or bounding one face at a time. In our

block-with-a-hole example, the user may first define the base of the block by specifying the

vertices, then connect them in order to bound the bottom surface. The user can then select the type
of surface to be fitted to these edges.

The following are descriptions of major surface entities provided by CAD/CAM systems:

4.9.1 3D FACE

3DFACE creates a three or four sided surface anywhere in 3D space. You can specify different Z

coordinates for each corner point of a 3D face. 3DFACE differs from SOLID, which creates a three
or four-sided surface that is parallel to the current UCS and can be extruded.

3D Wireframe lines 3D Face

4.9.2 TABULATED SURFACE

With the TABSURF command, you can create a mesh that represents a general tabulated surface

defined by a path curve and a direction vector. The path curve can be a line, arc, circle, ellipse,

elliptical arc, 2D polyline, 3D polyline, or spline. The direction vector can be a line or an open 2D or
3D polyline.

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