autocad 2009 second level 3d fundamentals bsie chapter 16.pptx

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Part III: Drawing in Three Dimensions

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3DDrawing

Chapter 16: Specifying 3D

Coordinates

IN THIS CHAPTER

Understanding 3D drawings

Working with 3D coordinates

Using elevation and thickness


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3DDrawing Working in a 3D Environment

To use the 3D template, choose Menu BrowserFileNew. In the Select

Template dialog box, choose acad3D.dwt (or acadiso3D.dwt for metric

drawings) and click Open. The tool palettes open and the panels on the

ribbon tabs change as well. In figure on the next slide, you see the result,minus the tool palettes, which was closed to display more of the drawing

area.

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From the Workspace Switching pop-up menu, choose 3D Modeling.

This displays the Dashboard with 3D commands.


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3DDrawing Using 3D Coordinates

All the 2D methods of specifying coordinates have their 3D counterparts.

Absolute coordinatesare the same in 3Dyou just add a Z coordinate. In

the same way, you can specify relative coordinates. In 3D drawings, you can

use two new types of coordinates that are 3D counterparts of polarcoordinates, cylindricaland spherical.

Cylindrical and Spherical Coordinates

Just as polar coordinates are often more useful than Cartesian coordinatesin 2D, cylindrical and spherical coordinates can be more useful in 3D. Heres

how they work.

Cylindrical coordinates have the format (@)distance


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3DDrawing The first distance is the number of units in the XY plane from the origin

(for absolute coordinates) or your last point (for relative coordinates).

The angle is the number of degrees from the X axis in the XY plane.

The second distance is the number of units along the Z axis.

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3DDrawing When you draw a line using cylindrical coordinates, neither distance that

you specify is the length of the line. In essence, youredefining the lengths

of two sides of a triangle to draw the hypotenuse. Figure below shows an

example of a line drawn with cylindrical coordinates. The line was drawn

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3DDrawing from 0,0,0 to 5


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3DDrawing Therefore, the hypotenuse is the square root of 25 + 9 or 34, which is

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3DDrawing Spherical coordinates have the format (@)distance


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3DDrawing When you draw a line using spherical coordinates, the first distance is the

actual length of the line. Figure below shows an example of a line drawn

with spherical coordinates. The line was drawn from 0,0,0 to 5


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3DDrawing Creating 3D Polylines

Youve already created 3D lines by specifying 3D coordinates for the

endpoints. One command that has a 3D counterpart is PLINE. The 3D

command is 3DPOLY (Menu BrowserDraw3D Polyline). The 3DPOLY

command is like the PLINE command with a few differences:

You cannot draw arcs.

You cannot give the polyline a width.

You cannot use a noncontinuous linetype.

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3DDrawing Creating Helixes

You can create a wireframe helix, or spiral, by using the HELIX

command. In the 3D Modeling workspace, choose Home tabDraw

panelHelix.

When you start the command, an initial message indicates the default

number of turns and the direction of the twist (clockwise or

counterclockwise).

Follow the prompts:

Specify center point of base: Specify the center point for the base at

the bottom of the helix.

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3DDrawing Specify base radius or [Diameter] : Enter a radius (or diameter)

using the option. The default is the last radius you used.

Specify top radius or [Diameter] : Enter a radius for the top of

the helix.

Specify helix height or [Axis endpoint/Turns/turn Height/tWist] :

Enter a height to use the default number of turns. You can also use the

options to change the number of turns and the direction of the twist. You

can specify the height by specifying an axis endpoint (the center of the

top of the helix) or the turn height.

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3DDrawing Figure below shows a helix with five turns. You can grip-edit the helix to

increase its height. Chapter

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3DDrawing Using Elevation and Thickness

Wireframes have a number of limitations. Also, creating the detail of a real

chair would be tedious if you were to use individual lines or 3D polylines.

Finally, wireframes dont have any surface or solid properties. You cant

display them in any realistic fashion or calculate properties, such as area,mass, and so on.

Creating surfaces with thickness

You can create simple surfaces by adding thickness to 2D objects. When

you add thickness to a 2D object, the object is pushed out into the third

dimension. For example, a circle becomes a cylinder and a rectangle

becomes a box. Remember that you wont see the thickness if youre

looking at the object from the top.

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3DDrawing Figure below shows some objects created using thickness.

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3DDrawing To add thickness to an existing 2D object, display the Properties palette

(Ctrl+1) and select the object. (You can also select the object first.) In the

palette, click the Thickness property and change the number in the

Thickness text box. Press Enter.

Adding elevation to objects

Until now, weve discussed 3D objects based on 2D objects that were on

the XY plane. In other words, their Z coordinate was zero. Although you

generally dontwant objects to float in the air, you certainly may want to

place one object on top of another. To do this, you need to start the object

above the XY plane (you can also place objects below the XY plane) and

give an object elevation, which is its Z coordinate.

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3DDrawing To give elevation to an existing object, you can use this method:

Select the object and display the Properties palette (Ctrl+1). Click the

Elevation property, type a new elevation in the text box, and press Enter.

For new objects, change the current elevation with the ELEV command.When you change the current elevation, all objects that you create are

drawn on that elevation. Remember to change the elevation back to zero

when you want to draw on the XY plane again.

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3DDrawing Working with the User Coordinate System (UCS)

Much of 3D work starts with a 2D shape. However, the 2D drawing

commands can be drawn only on, or parallel to, the XY plane. For example,

the spool in figure below consists of three circles, all parallel to the XY

plane. How do you draw a circle, or any other 2D object for that matter,that is not parallel to the XY plane?

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3DDrawing The answer is to change the User Coordinate System (UCS), thereby

changing the definition of the XY plane. You can move the UCS to any

location to define the XY plane in any way that you want. After you do so,

you can draw a 2D object at any angle.

Using the UCS icon

Although you may have found the UCS icon an annoyance in 2D work, you

should display it when working in 3D. Otherwise, itseasy to lose track of

which direction is which. Remember that you can choose the Origin option,

which displays the UCS icon, if possible, at the origin. Choose Menu

Browser View Display UCS Icon Origin. You can also choose

View tabUCS panel (expanded)Display UCS Icon.

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3DDrawing Using the UCS options to change the UCS

To change the UCS, choose View tabUCS panel, and choose one of

the options. (Some are on the expanded panel.) The following UCS

options are useful for 3D drawing.

3Point

The first point that you specify is the origin, the second point indicates

the positive direction of the X axis, and the third point indicates the

positive direction of the Y axis.

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3DDrawing

Chapter

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Summary

In this chapter you learned the following:

Understanding all the types of 3D coordinates and how to use them

Utilizing elevation and thickness

Working with User Coordinate Systems in 3D


autocad 2009 second level 3d fundamentals bsie chapter 16.pptx

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