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Objective

To create 3D wireframe models using AutoCAD. To create drawings using Layouts (paper space) and model space commands in AutoCAD. This assignment is in two parts.

A wireframe model is a skeletal description of a 3D object. There are no surfaces in a wireframe model; it consists only of points, lines, and curves that describe the edges of the object. With AutoCAD you can create wireframe models by positioning 2D (planar) objects anywhere in 3D space. AutoCAD also provides some 3D wireframe objects, such as 3D polylines (that can only have a CONTINUOUS linetype) and splines. Because each object that makes up a wireframe model must be independently drawn and positioned, this type of modeling can be the most time-consuming.

Exercise Part A:

1.Start a new drawing and set units to architectural.

2.Create a 1” wireframe cube.

Rotate the XY drawing plane to an axonometric view. Use “View-3D Views-VPORT” or any of the other viewing options. Use the LINE command to sketch a 1"x1" square at the origin: (0,0,0), (1,0,0), (1,1,0), (0,1,0).

Sketch another square at an elevation (Z) of 1": (0,0,1), (1,0,1), (1,1,1), (0,1,1).

Set object snapping to "ENDpoint" and use the LINE command to add the vertical lines, connecting corresponding points on the top and bottom squares.

3.Label the top, front and side faces of the cube. Use the UCS and TEXT commands to achieve this.

4.Make single plots of at least two different views of the wireframe cube.

5.Make an object by offsetting and trimming the wireframe cube.

Remove the text from the cube. Use OFFSET, TRIM, UCS, and LINE to transform the cube into a new model. HIDE and Plot. Command HIDE should have no affect since the model is wireframe and has no occluding faces.

  1. Build four pieces of wireframe furniture to scale.

(You can instead model two of the mechanical parts from the previous assignment.)

No credit will be given for surface or solid models. Do not start with the cube unless you scale it first.

7.Create a furniture grouping with your furniture in it.

Plot a one- and two-point perspective of the furniture grouping. (Use either the DVIEW command and do not forget to set a “Distance”, or the “Orbit” subsystem.) Pay careful attention to the presentation of DVIEW and Orbit in class for steps necessary to produce one- and two-point perspectives. (I think Orbit is officially called “3D Orbit.”)

Exercise Part B:

In this exercise we will explore using “Layout viewports” in AutoCAD. This subject was partly covered in CAD Fundamentals I, so you should already be familiar with the general concepts. For those with short memories, here is a little refresher.

AutoCAD provides two different kinds of viewports, which can be rather confusing. The older system of viewports, called “tiled viewports” exists even in prior versions of AutoCAD. Tiled viewports can be set up using the “View-Viewports” command when in model space, and are merely a convenience for drawing and modeling purposes. They cannot be moved around in the drawing area, nor can they be plotted.

The newer system of viewports, which we will refer to here as “Layout viewports,” was introduced in Release 12 (as “paper space”), and is much more useful. It facilitates the manipulation of graphical properties and relative positions of objects in viewports, and the manipulation of the viewports themselves. It also makes it possible to plot viewports. We will only deal with Layout viewports here.

You have to understand two related concepts to use Layout viewports. The first is the concept of “paper space” (as opposed to “model space”). Paper space is the AutoCAD parallel universe where you can only draw things in two dimensions (just as you would on a piece of paper.) Model space, which you know by now, will allow you to draw anything at full scale in three dimensions. Things drawn in paper space have their own set of controlling setup parameters like drawing limits. Since things drawn in paper space are primarily intended to embellish the plotted output, it is most convenient to use the same size and units of the plotting medium, US letter size or 11x17 paper in our case. You use the Layout tab on the bottom edge of the drawing window to switch to paper space. Notice that the UCS icon turns into a triangle.

Now for the confusing part: AutoCAD will allow you to both see into your model space world, and manipulate it when you are in paper space, by allowing you to create Layout space viewports. In essence, Layout space viewports are like holes in your sheet of paper, through which you can not only see the model space underneath, but also reach in and alter the model space objects. To edit model space objects in a Layout space viewport, you use the MSPACE command while the triangle icon of layout space is still visible. This will put you in what we refer to below as “model space edit mode.”

8.Create a single Layout view.

Switch to paper space using the Layout tab.

Create a Layout viewport using “View-Viewports.” Set the lower left corner to 0,0 and the upper right corner to 10.5,8 (or larger if you intend to plot at 11x17.)

Use the Paper/Model button on the Status bar to switch to editing the model space view in the viewports Use ZOOM to scale the viewport to an appropriate scale. Click insidethe viewport to edit the model space contents.

9.Add a prismed RECTANGLE next to the object. Make sure you give it a reasonable THICKNESS.

The only purpose the extruded rectangle serves is to provide proof that you have created wireframe furniture pieces and not surfaces or solids. By producing a hidden line-free drawing (see below) you will see the extruded rectangle with hidden lines removed and clipped, and the wireframe furniture still showing all lines. If your furniture shows hidden lines removed, you have built the furniture using something other than the LINE, ARC, SPLINE, etc. tools.

10.Preview the viewport.

Make sure you are still in paper space, and that you are in model space edit mode (one of the model space icons should be visible inside the viewport). If not, use the Paper/Model button to get there. Use the PLOT dialog and its “Plot Preview” option.

11.Preview thedrawing with hidden lines removed.

Use the Paper/Model button to switch to paper space (the triangle icon will become visible). Use the right mouse button to bring up the local menu and choose “Properties.” Set the “Hide plot” property to “Yes.” This time, the entire drawing should be visible, and the prism should have its hidden lines removed.

12.Add dimensions.

Use MSPACE to switch to model space edit mode. Create a new layer for a set of dimensions.

Hint: Set the UCS to an appropriate location before dimensioning. It is not necessary to completely dimension the furniture piece.

14.Use the same technique to add dimensions toeither the side or front (that is, dimensions that project in a side or front view).

15.Assign the viewport border to its own layer.

Create a layer, say BORDER, and add the viewport border to it. You must be in paper space edit mode. Freeze the BORDER layer. Notice that only the border frame is frozen; the model space contents of the viewport are still shown.

  1. Add annotations while in paperspace

This should at least be a border and title.

  1. Create a plot of the dimensioned drawing

As the figure shows, you may zoom in on the area that has the dimensions.

  1. Plot an un-dimensioned drawing.

CAD Fundamentals IIWireframe ModelingAutoCAD