Learning Outcomes

When you have completed this module, you will be able to: Apply the TRIM and EXTEND commands when trimming and extending in three dimensional wireframe modeling. Apply the ROTATE3D command to rotate 3D models.

Rotating in 3D

AutoCAD has individual 2D and 3D rotate commands. The 2D rotate command is ROTATE and in 3D, it is ROTATE3D. In this module, using the ROTATE3D command will be taught. It is used to rotate the model in 3D space. The main difference between the two commands is that the ROTATE command uses a XY point to rotate around and the ROTATE3D command uses two XYZ points or an axis to rotated around. The ROTATE command can be used while 3D modeling as long as all of the objects being rotated are 2D objects and located on the current UCS. If 3D objects are going to be rotated in 3D space, the ROTATE3D command must be used. See Figure 8-1.

AutoCAD Command: ROTATE3D

The ROTATE3D command is used to rotate objects in 3D space around an axis or two XY points. Shortcut: none

WORK ALONG: Rotating Wireframe Models in 3D Space

Step 1

Using the NEW command, start a new drawing using the template: 3D Layout English.

Step 2

Save and name the drawing: AutoCAD 3D Workalong 08-1.

Step 3

On layer: Model, draw a wireframe model of the object shown in the multiview drawing. (Figure Step 3A and 3B)

Step 4

Enter the commands, as shown below, to set the TRIM and EXTEND commands while working in 3D.

Command: TRIM

Current settings: Projection=None, Edge=No Extend

(Note how in this case, the Projection is set to None and Edge to No Extend. Your computer might be different.)

Select cutting edges … (Select an object, any object)

Select objects or <select all>: (Press Enter)

Select object to trim or shift-select to extend or [Fence/Crossing/Project/Edge/eRase/Undo]: P

Enter a projection option [None/Ucs/View] <None>: U

(Enter U for Ucs.)

[Fence/Crossing/Project/Edge/eRase/Undo]: E

Enter an implied edge extension mode [Extend/No extend] <No Extend>: E

(Enter E for Edge and then another for Extend. That means that the intersection of the two objects that you are trimming or extending do not have to physically intersect. AutoCAD will extend them to find the apparent intersection for you.)

Command: EXTEND

Current settings: Projection=Ucs, Edge=Extend

Select cutting edges …

Select objects or <select all>:

(By entering the EXTEND command, you will now see the settings are set for this command as well.)

Command:

AUTHOR’S COMMENTS: The way the TRIM and EXTEND commands projects into 3D space can be configured in your AutoCAD software. These settings are saved in the registry which means they will affect all drawings modified on your computer. You only are required to set either the TRIM or the EXTEND command and the settings will be used by both. Complete Step 4 to set your TRIM and EXTEND commands for the AutoCAD 3D book.

Step 5

Enter the TRIM command as shown below. The Current settings: should be set as shown. If not, go back and redo Step 4. If they match, abort the command.

Command: TRIM

Current settings: Projection=UCS, Edge=Extend

Select boundary edges …

Step 6

Enter the ROTATE3D, as shown below, to rotate the model 90 degrees counterclockwise around the X axis. (Figure Step 6)

Command: ROTATE3D

Current positive angle: ANGDIR=counterclockwise ANGBASE=0

Select objects:

Specify opposite corner: 22 found

(Using a window, select all the objects)

Select objects:

Specify first point on axis or define axis by [Object/Last/View/Xaxis/Yaxis/Zaxis/2points]: X

(Rotate around the X axis.)

Specify a point on the X axis <0,0,0>:

(Press Enter to select 0,0,0 as the base point of the rotation.)

Specify rotation angle or [Reference]: 90

(The angle is positive since looking along the X axis towards 0,0,0, counterclockwise is the direction you want to rotate.)

Command:

AUTHOR’S COMMENTS: Unlike the ROTATE command, where the objects are rotated around a point, the ROTATE3D command rotates the objects around two XYZ points or an axis.

Step 7

Using what you learned in Step 6, rotate the model 90 degrees around the Y axis. This rotation will have be negative 90 degrees since the rotation is clockwise. (Figure Step 7)

AUTHOR’S COMMENTS: To find whether the rotation direction is either counterclockwise or clockwise, look at 0,0,0 from the positive end of the axis that you are rotating around.

Step 8

Change the UCS to the front and locate it at the centre of the circle. (Figure Step 8)

Step 9

On layer: Construction, draw a line from 0,0,0 at any angle and any length. The line you draw does not have to match the figure exactly. Draw it by eye. (Figure step 9)

Step 10

Change to the Front view to ensure that the line was drawn correctly. (Figure Step 10)

MUST KNOW: The TRIM and EXTEND commands should have the following default settings when working in 3D: Current settings: Projection=UCS, Edge=Extend

Step 11

Change the current view to SE Isometric and enter the ROTATE3D command, as shown below, to rotate the model using the Reference option. (Figure Step 11)

Command: ROTATE3D

Current positive angle: ANGDIR=counterclockwise ANGBASE=0

Select objects:

(Select all of the model objects in a window. Do not include the reference line that you just drew in the selection.)

Specify opposite corner: 22 found

Select objects:

Specify first point on axis or define axis by

[Object/Last/View/Xaxis/Yaxis/Zaxis/2points]: Z

(Rotating around the Z axis.)

Specify a point on the Z axis <0,0,0>:

Specify rotation angle or [Reference]: R

Specify the reference angle <0>: (cen) P1

Specify second point: (cen) P2

Specify the new angle: (cen) P1

(Note that you have to select the P1 location twice.)

Specify second point: (end) P3

Command:

MUST KNOW: Unlike the ROTATE command where the object is rotated around a point, the ROTATE3D uses two XYZ points to rotated around. You can use the X, Y or Z axis or two endpoints of a line.

Step 12

The wireframe model should now appear as shown in Figure Step 12A. Change the current view to Front to ensure that the model was rotated correctly. (Figure Step 12A and 12B)

AUTHOR’S COMMENTS: There is no key for this workalong and any future workalongs in theAutoCAD 3D book. Keys are supplied are for the lab exercises. The reason for this is I want to slowly remove your reliance on using keys to check the accuracy of your models. Since keys are not available to you after you complete this book, you must learn how to check the accuracy of your models on your own.

Step 13

Save and close the drawing.

USER TIP: When using the ROTATE3D command, ensure that the ANGDIR and ANGBASE system variables are set as shown below. These setting will display when you enter the command, as you can see below. After you become more familiar using 3D, you can change these settings. While working on the AutoCAD 3D book, leave them set as shown. Command: ROTATE3D Current positive angle: ANGDIR=counterclockwise ANGBASE=0

Key Principles

Key Principles in Module 8

While working in 3D, the TRIM and EXTEND commands should have the following default settings: Projection=UCS, Edge=Extend The ROTATE command, used for a 2D rotate, uses a XY point to rotate For a 3D rotate using the ROTATE3D command, one of the axises, a line or two XYZ points must be specified to rotate around. To find whether the 3D rotation direction is counterclockwise or clockwise, look at 0,0,0 from the positive end of the axis you are rotating around.

Lab Exercise 8-1

Time allowed: 60 minutes.

Drawing Name	Template	Units
AutoCAD 3D Lab 08-1	3D Layout English	Inches

Step 1

Draw all construction objects on layer: Construction and all model objects on layer: Model.

Step 2

Draw a wireframe model of the object shown in the figure. (Figure Step 2A, 2B, 2C,and 2D)

Step 3

When complete, freeze layer: Construction.

Step 4

Enter the UNITS command. In the Units dialogue box, set the Insertion Units to Inches. Change the location of the UCS to World and check the model with the key.

Step 5

Ensure that the USC is set to World and the current view is SE Isometric. (Figure Step 5)

Step 6

Rotate the model 90 degrees around the X axis. (Figure Step 6)

Step 7

Rotate the model 90 degrees around the Y axis. (Figure Step 7)

Step 8

Rotate the model 90 degrees around the X axis. (Figure Step 8)

Step 9

Rotate the model 90 degrees around the Z axis. (Figure Step 9)

AUTHOR’S COMMENTS: If you take note of where the WCS is located in each figure and where is was located in the previous figure, it will help you select which axis to rotate around.

Step 10

Save and close the drawing.

Lab Exercise 8-2

Time allowed: 40 minutes.

Drawing Name	Template	Units
AutoCAD 3D Lab 08-2	3D Layout English	Inches

Step 1

Draw all construction objects on layer: Construction and all model objects on layer: Model.

Step 2

Draw a wireframe model of the object shown in the figure. (Figure Step 2A, 2B, 2C, and 2D)

Step 3

When complete, freeze layer: Construction.

Step 4

Enter the UNITS command. In the Units dialogue box, set the Insertion Units to Inches. Change the location of the UCS to World and check the model with the key.

Step 5

Save and close the drawing.