Secondly, constructed wireframe entities have true 3D space coordinates, while the thickness approach creates entities with no true 3D coordinates.
First of all, we do not really extrude the wireframe entities instead we simply make copies of wireframe entities in the desired directions. This method is similar to the 2D extrusion approach illustrated in the previous chapter (Chapter 2) with several differences. The 2D Extrusion method involves making copies of 2D geometries in specific directions. The 3D wireframe model is typically completed by locating and connecting corners within the box. As the name implies, the Box method involves the creation of a 3D box with the edges constructed from the overall height, width and depth dimensions of the design. Two of the most commonly used methods for creating 3D wireframe models are the Box method and the 2D Extrusion method. With most CAD systems, creating 3D wireframe models usually starts with constructing 2D entities in 3D space. Note that 3D wireframe modelers are usually used in conjunction with surfacing modelers, which we will discuss in the later chapters of this text, to eliminate the problem of ambiguity. You should also realize that, in some cases, it could be quite difficult to locate some of the corner locations while creating a 3D wireframe model. A 3D wireframe model, also known as a stick-figure model or a skeleton model, contains only information about the locations of all the corners and edges of the design in space coordinates. The computer hardware requirements for wireframe modelers are typically much lower than the requirements for surface and solid modelers. Wireframe Ambiguity: Which corner is in front, A or B? The main advantage of using a 3D wireframe modeler to create 3D models is its simplicity. For example, in the figure displayed below, which corner is in front, corner A or corner B? The ambiguity problem becomes much more serious with complex designs that have many edges and corners. But because surface definition is not part of a wireframe model, all wireframe images have the inherent problem of ambiguity. The 3D wireframe models can be viewed from any direction as needed and are in general reasonably good representations of 3D design. Computer generated 3D wireframe models contain information about the locations of all the corners and edges in space coordinates. Introduction The first true 3D computer model created on CAD systems in the late 1970s was the 3D wireframe model. Input Options Using the View Toolbar Setup and Using the TRIM options Using the Setup Wizard Create Wireframe Models Apply the Box Method in Creating Models Construct with the Copy Command Understand the Available 3D Coordinates Visit the following websites to learn more about this book: AutoCAD 2012 Tutorial Second Level: 3D Modeling
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