712 Part IV Drawing in Three Dimensions

Summary

In this chapter, I covered all of the ways to view your 3D drawing. You read about:

Using the standard viewpoints on the Viewpoint flyout for a quick look.

Utilizing the DDVPOINT command to specify exact angles.

Using the tripod and compass for flexibility.

Using the PLAN command to quickly return you to plan view.

Shading your drawing in one of several modes — these shading modes persist until you turn them off.

Applying 3D orbit to view your model from any position. You can zoom and pan, create parallel and perspective views, and set clipping planes. You can also create a continuously moving orbit.

Using the DVIEW command to let you create parallel and perspective views. You set the camera and target where you can create front and back clipping planes.

Employing the three commands — SOLVIEW, SOLDRAW, and SOLPROF — that help you lay out views of a 3D drawing for plotting.

In the next chapter, I explain how to create 3D surfaces.

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Figure 23-2: A surface mesh.

When working with surfaces, you may want to display the Surfaces toolbar. Right-click any toolbar and choose Surfaces.

Drawing Surfaces with 3DFACE

Two-dimensional objects are often used to create three-dimensional models. In Chapter 21, I discuss how you can use 2D solids (the SOLID command), wide polylines, and circles to make horizontal surfaces when you add a thickness to them. In fact, the SOLID command is so useful in 3D that you can find its icon on the Surfaces toolbar.

You can also use regions in 3D drawings. Although regions are 2D objects and cannot be given a thickness, when you use the HIDE command, AutoCAD displays the region as a surface. When the drawing is regenerated to a wireframe display, the region is displayed as a wireframe again, losing its surface properties.

Another option is to use 3DFACE, which is a true 3D command. 3DFACE creates threeor four-sided surfaces that can be in any plane. You can place surfaces together to make a manysided surface. While AutoCAD draws lines between these surfaces, you can make the lines invisible to create the effect of a seamless surface. You define the surface by specifying the points that create the corners of the surface. As a result, a 3D face cannot have any curves. 3DFACE only creates surfaces — you cannot give a thickness to a 3D face. However, you can create a 3D solid from a 3D face using the EXTRUDE command. 3D solids are covered in the next chapter.

Using the 3DFACE command

To create a 3D face, choose 3D Face from the Surfaces toolbar. AutoCAD prompts you for first, second, third, and fourth points. You must specify points clockwise or counter-

clockwise, not in the zigzag fashion required by the 2D SOLID command. When creating a 3D face:

Press Enter at the Specify fourth point or [Invisible] <create three-sided face>: prompt to create a three-sided surface. Then press Enter again to end the command.

To create a four-sided surface, specify a fourth point. AutoCAD repeats the Specify third point or [Invisible] <exit>: prompt. Press Enter to end the command.

To create surfaces of more than four sides, continue to specify points. AutoCAD repeats the thirdand fourth-point prompts until you press Enter — twice after a third point or once after a fourth point.

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Making 3D face edges invisible

Making edges invisible makes a series of 3D faces look like one 3D face. Figure 23-3 shows three 3D faces with and without internal seams.

All edges visible

Internal edges invisible

Figure 23-3: You can make internal edges of a 3D face invisible.

You can control the visibility of 3D face edges in several ways.

Controlling visibility during 3D face creation

While you’re drawing the 3D face, you can right-click and choose Invisible before each edge. Then specify the next point. However, it’s sometimes difficult to predict exactly where to indicate the invisible edge.

Using the EDGE command

After creating the entire 3D face, you can use the EDGE command. The sole purpose of the EDGE command is to make 3D face edges visible and invisible — this is probably the easiest way to control the visibility of 3D face edges.

Choose Edge from the Surfaces toolbar. At the Specify edge of 3dface to toggle visibility or [Display]: prompt, select a visible edge that you want to make invisible.

AutoCAD repeats the prompt so that you can select additional edges. Press Enter to make the edges invisible. Although a visible edge might actually be two edges belonging to two adjacent 3D faces, EDGE makes them both invisible.

To make invisible edges visible, right-click and choose the Display option. AutoCAD displays all of the edges in dashed lines and shows the Enter selection method for display of hidden edges [Select/All] <All>: prompt. Press Enter to display all of the edges or use the Select option to select 3D faces (you can use windows for selection). Either way, you see

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the edges of the 3D face that you want to edit. AutoCAD then repeats the Specify edge of 3dface to toggle visibility or [Display]: prompt. You can now select the edge that you want to make visible. Press Enter to end the command and make the edge visible.

Using the Properties palette

After creating one or more 3D faces, you can also open the Properties palette (choose Properties on the Standard toolbar) and select one 3D face. You can choose more than one, but the results are difficult to predict.

Using this palette to edit 3D-face edge visibility presents two difficulties. First, you have no easy way of knowing which edge is which, because the palette only labels them Edge 1, 2, 3, and 4. Second, although the EDGE command makes both edges of adjacent 3D faces visible or invisible, the Properties palette does not. You need to use it for each adjacent face. The best method is to use the EDGE command to control visibility of 3D face edges.

Using the SPLFRAME system variable

Setting the SPLFRAME system variable to 1 and then regenerating the drawing makes all 3D face edges visible. (The SPLFRAME system variable also affects the display of spline-fit polylines, hence its name.) To return edges to their original setting, set SPLFRAME to 0 and do a REGEN.

STEPS: Drawing 3D Faces

1.Open ab23-a.dwg from the CD-ROM.

2.Save it as ab23-01.dwg in your AutoCAD Bible folder. This is a blank drawing with architectural units. Turn on ORTHO. OSNAP should be on. Set running object snaps for endpoints and midpoints. If the Surfaces toolbar is not displayed, right-click any toolbar, and check Surfaces.

3. Choose 3D Face from the Surfaces toolbar. Follow the prompts:

Specify first point or [Invisible]: 6,6 Specify second point or [Invisible]: @20,0

Specify third point or [Invisible] <exit>: @0,2'

Specify fourth point or [Invisible] <create three-sided face>: @–20,0 Specify third point or [Invisible] <exit>:

4.Start the COPY command. Follow the prompts:

Select objects: Select the 3D face. Select objects:

Specify base point or [Displacement] <Displacement>: Pick any point.

Specify second point of displacement or <use first point as displacement>: @0,0,1.5'

Specify second point of displacement or <use first point as displacement>: @0,0,3'

Specify second point of displacement or <use first point as displacement>:

You don’t see any difference because you’re looking at the three 3D faces in plan view and they’re on top of each other.

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5.Choose View 3D Views SE Isometric. Your drawing should look like Figure 23-4. You now have the top, bottom, and middle shelves of the cabinet.

3

6

2

7

4

5

1

8

Figure 23-4: The three 3D faces from an isometric viewpoint.

6.Start the 3DFACE command again. Follow the prompts:

Specify first point or [Invisible]: Pick the endpoint at 1 in Figure 23-4.

Specify second point or [Invisible]: Pick the endpoint at 2. Specify third point or [Invisible] <exit>: Pick the endpoint at 3. Specify fourth point or [Invisible] <create three-sided face>: Pick the endpoint at 4.

Specify third point or [Invisible] <exit>: Pick the endpoint at 5. Specify fourth point or [Invisible] <create three-sided face>: Pick the endpoint at 6.

Specify third point or [Invisible] <exit>: Pick the endpoint at 7. Specify fourth point or [Invisible] <create three-sided face>: Pick

the endpoint at 8.

Specify third point or [Invisible] <exit>:

7.To draw the door of the cabinet, change the current layer to CONST. Start the LINE command and draw a line from 2 in Figure 23-4 to @18<225. End the LINE command. Now start the COPY command and copy the line from 2 to 1. These two construction lines frame the door.

8.To make it easier to work on the door, choose Tools New UCS 3 Point. Follow the prompts:

Specify new origin point <0,0,0>: Pick the left endpoint of the bottom construction line.

Specify point on positive portion of X-axis <-0'-5 3/4",-0'-6 3/4",0'-0">: Pick 1 in Figure 23-4.

Specify point on positive-Y portion of the UCS XY plane <-0'-7 7/16",- 0'-6",0'-">: Pick the left endpoint of the top construction line.

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9.Start the LINE command again. Follow the prompts:

Specify first point: Choose the From object snap.

Base point: Pick the left endpoint of the top construction line.

<Offset>: @3,–3

Specify next point or [Undo]: Move the cursor to the right and type

12 .

Specify next point or [Undo]: Move the cursor down and type 30 .

Specify next point or [Close/Undo]: Move the cursor to the left and type 12 .

Specify next point or [Close/Undo]: c

Your drawing should look like Figure 23-5.

5 8

6 7

3

2

4 1

Figure 23-5: The partially completed cabinet.

10.Change the current layer to 0. Choose 3D Face from the Surfaces toolbar. Follow the prompts:

Specify first point or [Invisible]: Pick the endpoint at 1 in Figure 23-5.

Specify second point or [Invisible]: Pick the endpoint at 2. Specify third point or [Invisible] <exit>: Pick the endpoint at 3. Specify fourth point or [Invisible] <create three-sided face>: Pick the endpoint at 4. Notice the edge lines between 1 and 2 and between 3 and 4.

Specify third point or [Invisible] <exit>: Right-click and choose Invisible. Pick the endpoint at 5.

Specify fourth point or [Invisible] <create three-sided face>: Pick the endpoint at 6.

Specify third point or [Invisible] <exit>: Right-click and choose Invisible. Pick the endpoint at 7.

Specify fourth point or [Invisible] <create three-sided face>: Pick the endpoint at 8.

Specify third point or [Invisible] <exit>: Pick the endpoint at 1.