3D Modeling Types Available in AutoCAD

AutoCAD allows you to create three different types of 3D models: wireframe, surface, and solid. Each model type has strengths and weaknesses. When you want to create a presentation drawing of some sort, surface and solid 3D models are what you need; to create a solid or surface model, you can use a wireframe model as a template.

Wireframe model

Wireframe models are often referred to as 21⁄2D drawings because they aren’t 2D drawings in the true sense; they’re created with 2D objects but in 3D space. Wireframe models aren’t true 3D models because they lack faces, which allow objects that are beyond to be hidden when a 3D visual style is applied or a rendering is done. You can think of a wireframe model as being like a wire coat hanger or a chain link fence. Wireframe models are made up of standard 2D
objects that are given an additional coordinate value for the Z direction. You can use most 2D objects when creating a wireframe model, but objects such as lines, arcs, and circles are commonly used. The 2D objects are drawn in 3D using full X, Y, and Z coordinate values rather than just X and Y coordinate values. Figure-1 shows a wireframe model of a bracket that connects two parts together. The wireframe model is shown with the 3D Hidden visual style; all the individual 2D objects used to create the model are shown.


Surface model

Surface models are created from 3D objects called faces, which are true 3D objects in the sense that they contain a surface that can hide objects beyond them when a 3D visual style is applied or a rendering is done. Faces are created with three or four sides. Although the surface of a face can hide objects that are beyond it in the current view, they require some cleanup when shared edges are involved to provide a clean look that makes individual surfaces seem like a much larger surface.
AutoCAD offers a number of commands that allow you to create individual faces or primitive objects such as boxes, spheres, and cones. Figure-2 shows two surface models of the same bracket; the left model doesn’t have any of its edges cleaned up, whereas the right model has been cleaned up. The surface model is shown with the 3D Hidden visual style, and the objects closest to you in the current view hide the objects beyond them (unlike the wireframe model). Part IV covers surface models in greater depth.

Solid model

Solid models are created from 3D objects called solids, which are true 3D objects similar to faces that are used to make up surface models. 3D solids in AutoCAD are very different from surface models; these objects aren’t flat surfaces. Also unlike surface models, solid models don’t require additional cleanup of shared edges of the model because a 3D solid object is one continuous object instead of being made up of many different faces.
AutoCAD offers a number of commands that allow you to create primitive objects such as boxes, spheres, and cones along with editing the faces, edges, and bodies of a solid in many different ways. Figure-3 shows a solid model of a bracket. The solid model is shown with the 3D Hidden visual style, and the objects closest to you in the current view hide the objects beyond them (like a surface model does).