Chapter 23 /Getting Started with 3D
Learning Objectives:








Understand the use of three-dimensional (3D) drawing.
Understand various types of 3D models.
Understand the conventions in AutoCAD.
Use the DDVPOINT command to view the objects in the 3D space.
Use the VPOINT command to view the objects in the 3D space.
Understand various types of 3D coordinate systems.
Create surface models using various options.
Set the thickness and elevation for the objects.
Chapter 23 /Getting Started with 3D
 TYPES OF 3D MODELS
In AutoCAD, depending upon their characteristics, the 3D models are divided into three
types. They are:
• Wireframe Models
• Surface Models
• Solid Models
Learning
Objectives
Chapter 23 /Getting Started with 3D
• Wireframe Models
These are the models created using the simple
AutoCAD entities such as lines, polylines,
rectangles, polygons, or some other entities like
3D faces, and so on. These models consists of
only the edges and you can see through these
models. Wireframe models are generally used in
the bodybuilding of the vehicles.
A wireframe model
Learning
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Types Of
3D Models
Chapter 23 /Getting Started with 3D
• Surface Models
These are the models made up of one or more surfaces. These models have a negligible
wall thickness and are hollow inside. To understand these models, consider a wireframe
model with a cloth wrapped around it. This type of model is used in the plastic molding
industry, shoe manufacturing, utensils manufacturing and so on.
A surface model created
using a single surface
Learning
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A semifinished surface model created
using more than one surface
Types Of
3D Models
Chapter 23 /Getting Started with 3D
• Solid Models
These are the solid filled models having mass
properties. To understand a solid model,
consider a model made up of metal or wood.
You can perform boolean operations on these
models, cut a hole through them, or even cut
them into slices
A solid model
Learning
Objectives
Types Of
3D Models
Chapter 23 /Getting Started with 3D
 CONVENTIONS IN AutoCAD
It is important for you to know the conventions in AutoCAD before you proceed with the 3D.
AutoCAD follows these three conventions:
1.
Whenever you open a new drawing in AutoCAD, it is in the Plan view and whatever you
draw, it will be in the world XY plane.
2.
The right-hand rule states that if you keep the thumb, index finger, and the middle finger
of the right hand mutually perpendicular to each other as shown in figure (a), then the
thumb of the right hand displays the direction of the positive X axis, the index finger
displays the direction of the positive Y axis and the middle finger of the right hand
displays the direction of the positive Z axis, see figure (b).
Learning
Objectives
Figure (a) showing the
orientation of the fingers
Figure (b) showing the orientation
of the X, Y, and Z axes
Chapter 23 /Getting Started with 3D
3.
The right-hand thumb rule is followed in AutoCAD
to find out the direction of rotation or revolution in
the 3D space. It is very difficult to specify the
clockwise or the counterclockwise direction in the
3D space and, therefore, the right-hand thumb rule
is followed. The right-hand thumb rule states that if
the thumb of the right hand displays the direction
of the axis of rotation, then the direction of the
curled fingers will define the positive direction of
rotation, see figure.
Right-hand thumb rule showing the
axis and direction of rotation
Learning
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Conventions in
AutoCAD
Chapter 23 /Getting Started with 3D
 CHANGING THE VIEWPOINT TO VIEW THE 3D MODELS
In the Plan view, it is very difficult to find out
whether the object displayed is a 2D entity or a
3D model. For example, see the figure. In this
view it appears as though the object displayed is
a rectangle. The reason for this is that by default
you view the objects in the Plan view from the
direction of the positive Z axis. This is a very
confusing situation that has to be avoided.
Figure looking like a rectangle in
the Plan view
Learning
Objectives
Chapter 23 /Getting Started with 3D
In order to do that, you need to change the
viewpoint so that the object is displayed in the space
with all three axes as shown in the figure. In this
view you can also see the Z axis of the model along
with the X and the Y axes and so it is clear that the
original object is not a rectangle but is a 3D model.
The viewpoint can be changed by the
• DDVPOINT Command
• VPOINT Command
• View Toolbar
Viewing the 3D model
changing the viewpoint
Learning
Objectives
after
Chapter 23 /Getting Started with 3D
• Changing the Viewpoint Using the Viewpoint Presets Dialog Box
The DDVPOINT command is used to invoke the
Viewpoint Presets dialog box, which can be
used to set the viewpoint to view the 3D models.
The dialog box sets the viewpoint with respect to
the angle in the XY plane and the angle from
the XY plane. Figure shows different view
direction parameters.
View direction parameters
Learning
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Viewpoint
Chapter 23 /Getting Started with 3D
•
Viewpoint Presets Dialog Box Options
The options available in the Viewpoint Presets dialog box
(figure) are:
Absolute to WCS : This radio button is selected to set the
viewpoint with respect to the world coordinate system.
Relative to UCS : This radio button is selected to set the
viewpoint with respect to the current user coordinate
system (UCS).
From: X Axis : This edit box is used
to specify the angle in the XY plane
from the X axis. You can directly enter
the required angle in this edit box or
you can select the desired angle from
the image tile (figure). This value can
vary between 0 and 359.9.
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Viewpoint Presets dialog box
The image tile for selecting
the angle in the XY plane
DDVPOINT
Command
Chapter 23 /Getting Started with 3D
XY Plane : This edit box is used to specify the angle from the XY plane.
You can directly enter the desired angle in this edit box, or can select
the angle from the image tile as shown in the figure. This value can vary
from -90 to +90.
Set to Plan View : This button is chosen to set the viewpoint to the Plan
view of the WCS or the UCS. Figures given below show a 3D model
from different viewing angles.
Learning
Objectives
Viewing the 3D model
with the angle in the XY
plane as 225 and angle
from the XY plane as 30
Viewing the 3D model
with the angle in the XY
plane as 145 and angle
from the XY plane as 25
The image tile for
selecting the angle
from the XY plane
VPOINT Dialog
Box Options
Chapter 23 /Getting Started with 3D
• Changing the Viewpoint Using the Command Line
The VPOINT command is also used to set the viewpoint for viewing the 3D models. This
command allows the user to specify a point in the 3D space that will act as the viewpoint.
Its various options are:
• Specifying a Viewpoint
• Compass and Tripod
• Rotate
Learning
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Viewpoint
Chapter 23 /Getting Started with 3D
•
Specifying a Viewpoint
This is the default option and is used to set a viewpoint by specifying the location of the
viewpoint using the X, Y, and Z coordinates of that particular point. AutoCAD follows a
conventions of the sides of the 3D model for specifying the viewpoint. The convention
states that if the UCS is at the World position (default position), then:
1. The side at the positive X axis direction will be taken as the right side of the model.
2. The side at the negative X axis direction will be taken as the left side of the model.
3. The side at the negative Y axis direction will be taken as the front side of the model.
4. The side at the positive Y axis direction will be taken as the back side of the model.
5. The side at the positive Z axis direction will be taken as the top side of the model.
6. The side at the negative Z axis direction will be taken as the bottom side of the model.
Learning
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Chapter 23 /Getting Started with 3D
The following figures show 3D model from different viewpoints:
Viewing the model with
the viewpoint -1,-1, 1
Learning
Objectives
Viewing the model with
the viewpoint 1, 1, 1
Viewing the model with
the viewpoint -1, 1, 1
Viewing the model with
the viewpoint 1,-1, 1
VPOINT
Command
Chapter 23 /Getting Started with 3D
•
Compass and Tripod
When you press ENTER at the Specify a
viewpoint or [Rotate] <display compass
and tripod> prompt, a compass and an axis
tripod is displayed as shown in the figure. You
can directly set the viewpoint using this
compass. The crosshairs appears on the
compass and you can pick any point on this
compass to specify the viewpoint. The
compass consists of two circles, a smaller
circle and a bigger circle. Both of these circles
are divided into four quadrants: first, second,
third, and fourth. The resultant view will
depend upon the quadrant and the circle on
which you select the point.
Learning
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The Axis tripod and the compass
Chapter 23 /Getting Started with 3D
In the first quadrant, both the X and Y axes are positive; in the second quadrant, the X axis is
negative and the Y axis is positive; in the third quadrant, both the X and Y axes are negative;
and in the fourth quadrant, the X axis is positive and the Y axis is negative. Now, if you select
the point inside the inner circle, it will be in the positive Z axis direction and if you select the
point outside the inner circle and inside the outer circle, it will be in the negative Z axis direction.
Therefore, if the previously mentioned statements are added, the following is concluded.
1.
If you select a point inside the smaller circle in the first
quadrant, the resultant view will be the Right, Back, Top
view. If you select a point outside the smaller circle and
inside the bigger circle in this quadrant, the resultant view
will be the Right, Back, Bottom view (figure).
2.
If you select a point inside the smaller circle in the second
quadrant, the resultant view will be the Left, Back, Top
view. If you select a point outside the smaller circle and
inside the bigger circle in this quadrant, the resultant view
The directions for the compass
will be the Left, Back, Bottom view (figure).
Learning
Objectives
Chapter 23 /Getting Started with 3D
3.
If you select a point inside the smaller circle in the third quadrant, the resultant view
will be the Left, Front, Top view. If you select a point outside the smaller circle and
inside the bigger circle in this quadrant, the resultant view will be the Left, Front,
Bottom view (figure).
4.
If you pick a select inside the smaller circle in the fourth quadrant, the resultant view
will be the Right, Front, Top view. If you select a point outside the smaller circle and
inside the bigger circle in this quadrant, the resultant view will be the Right, Front,
Bottom view (figure).
Learning
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VPOINT
Command
Chapter 23 /Getting Started with 3D
•
Rotate
This option is similar to setting the viewpoint in the Viewpoint Presets dialog box displayed
by invoking the DDVPOINT command. When you select this option, you will be prompted to
specify the angle in the XY plane and the angle from the XY plane. The angle in the XY
plane will be taken from the X axis.
Learning
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VPOINT
Command
Chapter 23 /Getting Started with 3D
• Changing the Viewpoint Using the View Toolbar
Apart from the Viewpoint Presets dialog box and the VPOINT commands, you can also
set the viewpoint using the View toolbar (figure). This toolbar consists of six preset
orthographic views: Top View, Bottom View, Left View, Right View, Front View, and Back
View. Apart from these orthographic views, this toolbar also has four preset isometric
views: Southwest Isometric View, Southeast Isometric View, Northeast Isometric View, and
Northwest Isometric View.
View toolbar
Learning
Objectives
Viewpoint
Chapter 23 /Getting Started with 3D
 3D COORDINATE SYSTEMS
Similar to the 2D coordinate systems, there are two main types of coordinate systems. They
are as follows.
• Absolute Coordinate System
• Relative Coordinate System
Learning
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Chapter 23 /Getting Started with 3D
• Absolute Coordinate System
This type of coordinate system is similar to the 2D absolute coordinate system in which the
coordinates of the point are calculated from the origin (0,0). The only difference is that here
along with the X and Y coordinates, the Z coordinates are also included. For example, if you
want to draw a line in 3D space starting from the origin to a point say 10,6,6, the procedure
to be followed is:
Command: LINE
Specify first point: 0,0,0
Specify next point or [Undo]: 10,6,6
Specify next point or [Undo]: «
Figure shows the model drawn using the absolute
coordinate systems.
Learning
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Drawing a line from origin to
10,6,6
3D Coordinate
Systems
Chapter 23 /Getting Started with 3D
 Example 1
In this example you will draw the 3D wireframe
model shown in the figure.
1.
Choose the Line button from the Draw
toolbar. The prompt sequence is as follows:
Specify first point: 2,2,0
Specify next point or [Undo]: 8,2,0
Specify next point or [Undo]: 8,6,0
Specify next point or [Close/Undo]: 2,6,0
Specify next point or [Close/Undo]: C
3D wireframe model for Example 1
Learning
Objectives
Chapter 23 /Getting Started with 3D
2.
Choose 3D Views > Viewpoint Presets from the View
menu to display the Viewpoint Presets dialog box (figure).
3.
Set the value of the X Axis edit box to 225. Set the value of
the XY Plane edit box to 38. Choose OK.
4.
Set the value of the XY Plane edit box to 38. Choose OK.
5.
Choose the Line button from the Draw toolbar. The prompt
sequence is as follows:
Specify first point: 2,2,0
Specify next point or [Undo]: 2,2,2
Specify next point or [Undo]: 2,4,2
Specify next point or [Close/Undo]: 8,4,2
Specify next point or [Close/Undo]: 8,2,2
Viewpoint Presets dialog
box
Specify next point or [Close/Undo]: 2,2,2
Specify next point or [Close/Undo]: «
Learning
Objectives
Example 1
Chapter 23 /Getting Started with 3D
6.
Choose the Line button from the Draw toolbar. The prompt sequence is as follows:
Specify first point: 2,4,2
Specify next point or [Undo]: 2,4,4
Specify next point or [Undo]: 2,6,4
Specify next point or [Close/Undo]: 2,6,0
Specify next point or [Close/Undo]: «
7.
Choose 3D Views > Viewpoint Presets from the View menu to display the Viewpoint
Presets dialog box.
8.
Set the value of the X Axis edit box to 335.
9.
Set the value of the XY Plane edit box to 35. Choose OK.
10. Choose the Line button from the Draw toolbar. The prompt sequence is as follows:
Specify first point: 8,2,0
Specify next point or [Undo]: 8,2,2
Specify next point or [Undo]: «
Learning
Objectives
Example 1
Chapter 23 /Getting Started with 3D
11. Choose the Line button from the Draw toolbar. The prompt sequence is as follows:
Specify first point: 8,4,2
Specify next point or [Undo]: 8,4,4
Specify next point or [Undo]: 8,6,4
Specify next point or [Close/Undo]: 8,6,0
Specify next point or [Close/Undo]: «
12. Choose the Line button from the Draw toolbar. The prompt sequence is as follows:
Specify first point: 8,6,4
Specify next point or [Undo]: 2,6,4
Specify next point or [Undo]: «
13. Choose the Line button from the Draw toolbar. The prompt sequence is as follows:
Specify first point: 8,4,4
Specify next point or [Undo]: 2,4,4
Learning
Objectives
Specify next point or [Undo]: «
Example 1
Chapter 23 /Getting Started with 3D
14. Enter VPOINT at the Command prompt. The prompt sequence is as follows:
Current view direction: VIEWDIR=0.7424,-0.3462,0.5736
Specify a viewpoint or [Rotate] <display compass and tripod>: -1,-1,1
15. The final model should look similar to the one shown in the figure.
Learning
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Final 3D model for Example 1
Example 1
Chapter 23 /Getting Started with 3D
• Relative Coordinate System
In the 3D, you are provided with three types of relative coordinate systems. They are as
follows.
• Relative Rectangular Coordinate System
• Relative Cylindrical Coordinate System
• Relative Spherical Coordinate System
Learning
Objectives
3D Coordinate
Systems
Chapter 23 /Getting Started with 3D
•
Relative Rectangular Coordinate System
This coordinate system is similar to the relative rectangular coordinate system, except that
in 3D you have to enter the Z coordinate also along with the X and the Y coordinates. The
syntax of the relative rectangular system for the 3D is @X coordinate,Y coordinate,Z
coordinate.
•
Relative Cylindrical Coordinate System
In this type of coordinate system you are allowed to
locate the point by specifying the distance of the
point from the reference point, the angle in the XY
plane, and its distance from the XY plane. The
syntax of the relative cylindrical coordinate system
is @Distance from the reference point in the XY
plane<Angle in the XY plane from the X axis,
Distance from the XY plane along the Z axis.
Various components of the relative
cylindrical coordinate system
Learning
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Relative Coordinate
System
Chapter 23 /Getting Started with 3D
•
Relative Spherical Coordinate System
In this type of coordinate system you are
allowed to locate the point by specifying the
distance of the point from the reference point,
the angle in the XY plane, and the angle from
the XY plane. The syntax of the relative
spherical coordinate system is @Length of the
line from the reference point<Angle in the
XY plane from the X axis<Angle from the XY
plane. Figure shows various components
involved in the relative spherical coordinate
system.
Various components of the relative
spherical coordinate system
Learning
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Relative Coordinate
System
Chapter 23 /Getting Started with 3D
 Example 2
In this example you will draw the 3D wireframe model
shown in the figure (a). The dimensions of the model
are given in the following figures (b) & (c).
Figure (a) Wireframe model
for Example 2
Figure (b) Front view of
the model
Learning
Objectives
Figure (c) Side view of
the model
Chapter 23 /Getting Started with 3D
1.
Choose the SW Isometric View button from the View
southwest isometric view.
2.
toolbar to shift
to the
As the start point of the model is not given, you can start the model from any point.
Choose the Line button from the Draw toolbar to invoke the LINE command. The prompt
sequence is as follows:
Specify first point: 4,2,0
Specify next point or [Close/Undo]: @0,0,-2
Specify next point or [Undo]: @0,0,2
Specify next point or [Close/Undo]: @3,0,0
Specify next point or [Undo]: @3,0,0
Specify next point or [Close/Undo]: @0,0,-2
Specify next point or [Close/Undo]: @0,0,2
Specify next point or [Close/Undo]: C
Specify next point or [Close/Undo]: @3,0,0
Specify next point or [Close/Undo]: @2<0<315
Specify next point or [Close/Undo]: @2<0<45
Specify next point or [Close/Undo]: @3,0,0
Learning
Objectives
Example 2
Chapter 23 /Getting Started with 3D
3.
4.
Choose the Line button from the Draw toolbar. The prompt sequence is as follows:
Specify first point: 4,2,0
Specify next point or [Close/Undo]: @3,0,0
Specify next point or [Undo]: @0,8,0
Specify next point or [Close/Undo]: @0,0,-2
Specify next point or [Undo]: @0,0,2
Specify next point or [Close/Undo]: @3,0,0
Specify next point or [Close/Undo]: @3,0,0
Specify next point or [Close/Undo]: @0,0,-2
Specify next point or [Close/Undo]: @2<0<315
Specify next point or [Close/Undo]: @0,-8,0
Specify next point or [Close/Undo]: @2<0<45
Specify next point or [Close/Undo]: «
Complete the model by joining the remaining edges using the LINE command.
Learning
Objectives
Example 2
Chapter 23 /Getting Started with 3D
5.
The final 3D model should look similar to the one shown in figure.
Final 3D wireframe model for Example 2
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Objectives
Example 2
Chapter 23 /Getting Started with 3D
 Exercise 1
In this exercise you will draw the 3D
wireframe model shown in the figure.
The dimensions for the model are given
in the figure itself. You can start the
model from any point.
Wireframe model for Exercise 2
Learning
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Chapter 23 /Getting Started with 3D
 TRIM, EXTEND, AND FILLET COMMANDS IN 3D
You can use various options of these commands in 3D space. You can also use the
PROJMODE and EDGEMODE variables. The PROJMODE variable sets the projection
mode for trimming and extending.
A value of 0 implies True 3D mode, that is, no projection. In this case the objects must
intersect in 3D space to trim or extend them. It is similar to using the None option of the
Project option of the EXTEND and TRIM commands.
A value of 1 projects onto the XY plane of the current UCS and is similar to using the UCS
option of the Project option of the TRIM or EXTEND commands.
A value of 2 projects onto the current view plane and is like using the View option of the
Project option of the TRIM or EXTEND commands.
Learning
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Chapter 23 /Getting Started with 3D
 SETTING THICKNESS AND ELEVATION FOR THE NEW
OBJECTS
You can use various options of these commands in 3D space. You can also use the
PROJMODE and EDGEMODE variables. The PROJMODE variable sets the projection
mode for trimming and extending. A value of 0 implies True 3D mode, that is, no projection.
In this case the objects must intersect in 3D space to trim or extend them. A value of 1
projects onto the XY plane of the current UCS and is similar to using the UCS option of the
Project option of the TRIM or EXTEND commands.
A value of 2 projects onto the current view plane and is like using the View option of the
Project option of the TRIM or EXTEND commands. The value of the EDGEMODE system
variable controls how the cutting or trimming boundaries are decided.
A value of 0 considers the selected edge with no extension.
A value of 1 considers an imaginary extension of the selected edge.
Learning
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You can fillet coplanar objects whose extrusion directions are not parallel to the
z axis of the current UCS by using the FILLET command.
Chapter 23 /Getting Started with 3D
 SETTING THICKNESS AND ELEVATION FOR THE NEW
OBJECTS
You can create the objects with a preset elevation or thickness using the ELEV command.
This command is discussed next.
• ELEV Command
This command is a transparent command and is used to set the elevation and
thickness for new objects. The following prompt sequence is displayed when you
invoke this command.
Specify new default elevation <0.0000>: Enter the new elevation value.
Specify new default thickness <0.0000>: Enter the new thickness value.
•
Elevation
•
Thickness
Learning
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Chapter 23 /Getting Started with 3D
•
Elevation
This option is used to specify the elevation value for
new objects. Setting the elevation is nothing but
moving the working plane from its default position.
By default, the working plane is on the world XY
plane. You can move this working plane using the
Elevation option of the ELEV command. However,
remember that the working plane can be moved only
along the Z axis (figure). The default elevation value
is 0.0 and you can set any positive or negative value
for elevation. All the objects that will be drawn
hereafter will be with the specified elevation. The
Elevation option sets the elevation only for the new
objects, and the existing objects are not modified
using this option.
Learning
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Object drawn with elevation
ELEV
Command
Chapter 23 /Getting Started with 3D
•
Thickness
This option is used to specify the thickness values
for the new objects. It can be considered as another
method of creating the surface models. Specifying
the thickness creates the extruded surface models.
The thickness is always taken along the Z axis
direction (figure). The 3D faces will be automatically
applied on the vertical faces of the objects drawn
with thickness. The Thickness option sets the
thickness only for the new objects and the existing
objects are not modified using this option.
Object drawn with thickness
Learning
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ELEV
Command
Chapter 23 /Getting Started with 3D
 SUPPRESSING THE HIDDEN EDGES
You need to manually suppress the hidden lines in the 3D model using the HIDE
command. When you invoke this command, all the objects on the screen are
regenerated and the 3D models are displayed with the hidden edges suppressed. If
the value of the DISPSILH system variable is set to 1, the model is displayed only
with the silhouette edges and the internal edges that have facets will not be
displayed. The hidden lines are again included in the drawing when the next
regeneration takes place. Figure (a) shows the surface model displaying the hidden
edges and figure (b) shows the surface model without the hidden edges.
Learning
Objectives
Figure (a) 3D models
displaying all the edges
Figure (b) Models with hidden
edges suppressed
Chapter 23 /Getting Started with 3D
 CREATING 3D POLYLINES
The 3DPOLY command is used to draw straight polylines in a 2D plane or in 3D space.
This command is similar to the POLYLINE command except that using this command you
can draw the polylines in the plane other then the XY plane also. However, this command
does not provide the Width or the Arc option, and therefore you cannot create a 3D
polyline with width or arc. The Close and the Undo options of this command are similar to
those of the POLYLINE command.
Learning
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Chapter 23 /Getting Started with 3D
 CONVERTING WIREFRAME MODELS INTO SURFACE
MODELS
Once you have created a wireframe model, you can convert it into a surface model using
the 3DFACE command and the PFACE command. These commands for converting a
wireframe model into a surface model are discussed next.
Learning
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Chapter 23 /Getting Started with 3D
• Creating 3D Faces
The 3DFACE command is used to
create 3D faces in the space. You can
create three-sided or four-sided faces
using this command. You can specify
the same or a different Z coordinate
value for each point of the face. When
you invoke this command, you will be
prompted to specify the first, second,
third, and the fourth point of the 3D
face. Keep in mind that the points must
be specified in the natural clockwise or
the counterclockwise direction to create
proper 3D face, see figure.
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3D faces applied to the wireframe model
Chapter 23 /Getting Started with 3D
However, in case of complex wireframe models (figure (a)), it is not easy to apply the 3D faces.
The reason for this is when you apply a 3D face, it generates edges about all the points that you
specify. These edges will be displayed on the wireframe model. You can avoid these unwanted
visible edges by applying the 3D faces with invisible edges. This is done by simply using the
Invisible option. Follow the same procedure for creating the other invisible edges (figure (b)).
Wireframe model with the
edges
Learning
Objectives
Wireframe
the edges
model
without
Converting Wireframe
models into Surface
models
Chapter 23 /Getting Started with 3D
• Creating Polyface Meshes
The PFACE command allows you to create a
mesh of any desired surface shape by
specifying the coordinates of the vertices and
assigning the vertices to the faces in the mesh.
The difference between them is that when you
use the 3DFACE command, you do not select
the vertices that join another face twice. With
the PFACE command, you need to select all
the vertices of a face, even if they are
coincident with vertices of another face. Also,
with this command, there is no restriction on the
number of faces and the number of vertices the
mesh can have.
Learning
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Using the PFACE command
Converting Wireframe
models into Surface
models
Chapter 23 /Getting Started with 3D
• Controlling the Visibility of the 3D Face Edges
This command is used to control the visibility of the selected edges of the 3D faces.
You can hide the edges of the 3D faces or display them using this command (figures
(a) and (b)). When you invoke this command, you will be prompted to specify the 3D
face edge to toggle the visibility or display. To hide an edge, select the edge, and to
display the edges, enter D at the Specify edge of 3dface to toggle visibility or
[Display] prompt.
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Figure (a) Model with visible 3D
face edges
Figure (b) Model after making
the edges invisible
Chapter 23 /Getting Started with 3D
 Exercise 2
In this exercise you will apply the 3D faces to
the 3D wireframe model created in Example 2
(figure).
Wireframe model created in Example 2
Learning
Objectives
Chapter 23 /Getting Started with 3D
 DIRECTLY CREATING THE SURFACE MODELS
The surface models created using the 3D faces consist only of straight edges. The surfaces
with the curved edges cannot be created using the 3D faces. However, in AutoCAD, you
can directly create various types of surface models consisting of straight edges or the
curved edges. All of these surface models along with the commands used to create them
are discussed next.
• Ruled Surfaces (RULESURF command)
• Tabulated Surfaces (TABSURF command)
• Revolved Surfaces (REVSURF command)
• Four-sided Polygon Mesh (EDGESURF command)
Learning
Objectives
Chapter 23 /Getting Started with 3D
• Creating Ruled Surfaces
The RULESURF command is used to create a ruled surface between two defining
entities. You can create a ruled surface between two closed entities, two open
entities, a point and a closed entity, and a point and an open entity. If the two
defining entities are open, the selection points matter. If you select the open entities
at the same end, it creates a straight polygon mesh, and if you select the open
entities at the opposite ends, it creates a self-intersecting polygon mesh as shown in
figures (a) and (b).
Learning
Objectives
Figure (a) Selecting objects
at same ends
Figure (b) Selecting objects
at opposite ends
Chapter 23 /Getting Started with 3D
The smoothness of the ruled surface can be increased using the SURFTAB1 system variable,
see figures. The default value of this system variable is 6 and it excepts any integer between 2
and 32766 as its value.
Ruled surface created keeping
the value of the SURFTAB1
system variable as 6
Learning
Objectives
Ruled surface created keeping
the value of the SURFTAB1
system variable as 50
Creating Surface
Model Options
Chapter 23 /Getting Started with 3D
• Creating Tabulated Surfaces
The TABSURF command is used to create tabulated surfaces using a path curve
along the direction defined by a direction vector. The entities that can be used as
base curves are lines, circles, arcs, splines, 2D polylines, 3D polylines, or ellipses.
The length of the tabulated surface will be equal to the length of the direction vector,
and the point used to select the direction vector will determine the direction of the
resultant surface, see figures.
Learning
Objectives
Direction of tabulated surface
Direction of tabulated surface
Chapter 23 /Getting Started with 3D
If the direction vector consists of more then one
segment, then all the intermediate points will be
ignored and an imaginary vector will be drawn
between the first and the last point on the
polyline. This imaginary vector is considered as
the direction vector and the tabulated surface is
created along this imaginary vector as shown in
the figure.
Direction of tabulated surface
Learning
Objectives
Creating Surface
Model Options
Chapter 23 /Getting Started with 3D
• Creating Revolved Surfaces
The REVSURF command is used to create revolved surface by revolving a path
curve about a specified axis of rotation. You can select an open entity or a closed
entity as the path curve. The direction of the revolution depends upon the side from
which you select the revolution axis. Since it is not possible to define the clockwise
and counterclockwise directions in the 3D space, therefore, AutoCAD uses the righthand thumb rule to determine the direction of revolution. Figure (a) shows a path
curve and a revolution axis and figure (b) shows the revolved surface.
Learning
Objectives
Figure (a) Selecting the object
to revolve and the axis of
revolution
Figure (b) The resultant
revolved surface
Chapter 23 /Getting Started with 3D
You can specify the start angle and the included angle for the revolved surface, see figures.
Revolved surface with start angle
as 0 and included angle as 270
Learning
Objectives
Revolved surface with start angle
as 25 and included angle as 180
Chapter 23 /Getting Started with 3D
The smoothness of the tabulated surface depends upon the value of the SURFTAB1 system
variable. AutoCAD draws tabulated lines in the direction of the revolution and the number of
tabulated lines is specified by the value of the SURFTAB1 system variable. If the revolved
surface is created using the path curve that is a line, arc, circle, spline, or a spline fit polyline,
then another set of lines are drawn to divide it into equal-sized surfaces. The number of
surfaces is defined using the SURFTAB2 system variable (figure).
Figure showing different values of SURFTAB1
and SURFTAB2 system variable
Learning
Objectives
Creating Surface
Model Options
Chapter 23 /Getting Started with 3D
• Creating Four-sided Polygon Mesh
This command is used to create a 3D polygon mesh using four adjoining edges
forming a topologically closed loop. The entities that can be selected as the edges
are lines, arcs, splines, open 2D polylines, or open 3D polylines. You can select the
edges in any sequence. The smoothness of the edge surface will depend on the
values of the SURFTAB1 and SURFTAB2 system variables. The edge selected first
will define the M direction (SURFTAB1 direction) and the other two edges that start
from the endpoint of the first edge will define the N direction (SURFTAB2 direction),
see figures.
Learning
Objectives
Selecting edges for edge
surface
Resultant edge surface
Creating Surface
Model Options
Chapter 23 /Getting Started with 3D
 Exercise 3
In this exercise you will create the table
shown in the figure using various types of
surfaces. Assume the dimensions for the
table.
Model for Exercise 3
Learning
Objectives
Chapter 23 /Getting Started with 3D
 DRAWING STANDARD SURFACE PRIMITIVES
Apart from creating the surface using the
previously mentioned commands, you can also
create some standard 3D surface primitives like
box, cone, dish dome, pyramid, torus, sphere,
mesh, and wedge. These standard surface
primitives can be created using the 3D command.
When you invoke this command by choosing
Draw > Surfaces > 3D Surfaces from the menu
bar, the 3D Objects dialog box will be displayed
as shown in figure. All the 3D surface primitives
that can be created using this command can also
be chosen directly from the Surfaces toolbar.
Learning
Objectives
• BOX
• DOME
• SPHERE
• CONE
• MESH
• TORUS
• DISH
• PYRAMID
• WEDGE
3D Objects dialog box
Chapter 23 /Getting Started with 3D
• Creating a Box-Shaped Surface Mesh
This option is used to create a 3D
polygon mesh in the shape of the box,
see figure. When you invoke this option,
you will be prompted to specify the
corner of the box. Once you specify the
corner of the box, you will be prompted
to specify the length, width, and the
height of the box.
3D box-shaped surface mesh
Learning
Objectives
Surface
Primitives
Chapter 23 /Getting Started with 3D
• Creating a Cone-Shaped Surface Mesh
This option is used to create a 3D polygon mesh in the shape of a cone.you can
draw a truncated cone or a pointed cone.
3D cone-shaped surface mesh
Learning
Objectives
Truncated 3D cone-shaped surface
Surface
Primitives
Chapter 23 /Getting Started with 3D
• Creating a Surface Mesh Dish
A dish is a hemisphere with the convex surface facing
toward the bottom. Just as in the case of the dome,
you can use any one of the methods described
previously for drawing surface mesh models to
construct a dish (figure).
• Creating a Surface Mesh Dome
3D surface dish
A dome is a hemisphere with the
convex surface facing up (toward the
top). You can create a surface mesh
model of a dome (figure) by using any
one of the methods for drawing surface
mesh models.
Learning
Objectives
3D surface dome
Surface
Primitives
Chapter 23 /Getting Started with 3D
• Creating a Planar Mesh
You can create a planar model of a mesh (figure).
The type of mesh obtained is also known as planar
mesh because the mesh is generated in a single
plane. Once you have specified the four corner
points, AutoCAD prompts you to specify the number
of rows (M) and the number of columns (N) of
vertices. The number of vertices in both directions
should be in the range of 2 to 256; that is, M and N
should lie in the range of 2 to 256.
3D Planar surface mesh
Learning
Objectives
Surface
Primitives
Chapter 23 /Getting Started with 3D
• Creating a Pyramid Surface Mesh
You can create a surface mesh model of a pyramid by using any one of the
methods for drawing surface meshes. Choose the Pyramid button in the Surfaces
toolbar. Its various options are:
• Pyramid with an Apex: Apex Point Option
• Pyramid with a Ridge: Ridge Option
• Pyramid with a Top: Top Option
• Tetrahedron with an Apex: Apex Option
• Flat-Topped Tetrahedron: Top Option
Learning
Objectives
Surface
Primitives
Chapter 23 /Getting Started with 3D
•
Pyramid with an Apex: Apex Point Option
The default option is the Apex point (figure). With this
option, you can specify the location of the apex of the
pyramid. You must enter the X, Y, Z coordinates to
specify the location of the apex or use the .X, .Y, .Z
filters. If you simply select a point on the screen, the X
and Y coordinates of the apex will assume the X and Y
coordinates of the point selected, and the elevation, or
the Z coordinate, will be the same as the Z coordinate of
the base points. Hence, the apex of the pyramid will
have the same elevation as the base of the pyramid.
Only if you are in the 3D space [for example, your
viewpoint is (1,-1,1)] you can specify the apex by
selecting a point on the screen.
Learning
Objectives
Surfaced pyramid with an apex
Pyramid Surface
Mesh
Chapter 23 /Getting Started with 3D
•
Pyramid with a Ridge: Ridge Option
This option (figure) can be invoked by entering R at the
Specify apex point of pyramid or [Ridge/Top] prompt.
When you enter this option, the most recently drawn line of
the base is highlighted. This indicates that the first point on
the ridge will be perpendicular to the highlighted line.
•
Pyramid with a Top: Top Option
Surfaced pyramid with a ridge
You can invoke this option (figure) by entering T at the
Specify apex point of pyramid or [Ridge/Top] prompt.
When you invoke this option, a rubber-band line is attached
to the first corner of the base. The rubber-band line stretches
from the corner point to the crosshairs. If you specify the
same location (coordinates) for all four top points, the result
is a regular pyramid with its apex at the location where all the
four top points are located.
Surfaced pyramid with a top
Learning
Objectives
Pyramid Surface
Mesh
Chapter 23 /Getting Started with 3D
•
Tetrahedron with an Apex: Apex Option
As mentioned before, with this option you can draw a
tetrahedron that has four triangular sides and an apex
(figure). Choose the Pyramid button in the Surfaces toolbar.
•
Flat-Topped Tetrahedron: Top Option
With this option, you can draw a
tetrahedron that has a flat top
(figure). This option can be
invoked by entering T at the
Specify
apex
point
of
tetrahedron or [Top] prompt.
Tetrahedron with an apex
Tetrahedron with a top
Learning
Objectives
Pyramid Surface
Mesh
Chapter 23 /Getting Started with 3D
• Creating a Spherical Surface Mesh
The spherical surface mesh (figure) has its
central axis parallel to the Z axis, and the
latitudinal lines are parallel to the XY plane of the
current UCS. You can also append AI_ as a prefix
to sphere and use it as a command.
• Creating a Surface Mesh Torus
Spherical surface mesh
A torus is like a thick, hollow ring.
You can create a surface mesh
model of a torus (figure) by using
any one of the methods for drawing
surface mesh models.
Learning
Objectives
Surfaced torus
Surface
Primitives
Chapter 23 /Getting Started with 3D
• Creating a Surface Mesh Wedge
You can draw a surface mesh model of a rightangled wedge (figure) by using any one of the
methods for drawing surface mesh models. For
example, you can initiate the creation of a 3D
surface mesh model of a wedge by entering the
3D command at the Command prompt and then
entering Wedge at the next prompt. You can also
choose the Wedge button from the Surfaces
toolbar.
3D wedge-shaped surface mesh
Learning
Objectives
Surface
Primitives
Chapter 23 /Getting Started with 3D
 3DMESH COMMAND
When you invoke this command, you will be
prompted to specify the size of the mesh in the M
direction and the N direction, where M X N will be
the total number of vertices in the mesh. Once
you have specified the size of the mesh in the M
and N directions, you will have to specify the
coordinates of each and every vertex individually.
Figure shows a 4 X 4 free-form mesh. This
command is mostly used for programming. For
general drawing, use the Mesh option of the 3D
command. The 3D polygon mesh is always open
in the M and N directions. You can edit this mesh
or the mesh created using the 3D command using
the PEDIT command.
Learning
Objectives
Free-form 3D mesh
Chapter 23 /Getting Started with 3D
 EDITING THE SURFACE MESH
The surface meshes can be edited using the PEDIT command, which is discussed next.
• PEDIT Command
You can also invoke this command using the shortcut menu displayed upon
selecting the surface mesh and right-clicking on it. Choose the Polyline Edit
option to invoke this command. The behavior of the PEDIT command differs,
depending on whether the object selected is a line, polyline, or a surface mesh.
• Edit Vertex
• Mopen
• Smooth Surface
• Nopen
• Desmooth
• Undo
• Mclose
• eXit
• Nclose
Learning
Objectives
Chapter 23 /Getting Started with 3D
•
Edit Vertex
This option is used for individual editing of the vertices of the mesh in the M direction or in
the N direction. When you invoke this option, a cross will appear on the first point of the
mesh and the following sub-options will be provided:
Next. This sub-option is used to move the cross to the next vertex.
Previous. This sub-option is used to move the cross to the previous vertex.
Left. This sub-option is used to move the cross to the previous vertex in the N direction of
mesh.
Right. This sub-option is used to move the cross to the next vertex in the N direction of
mesh.
Up. This sub-option is used to move the cross to the next vertex in the M direction of mesh.
Down. This sub-option is used to move the cross to the previous vertex in the M direction
of the mesh.
Learning
Objectives
Chapter 23 /Getting Started with 3D
Move. This sub-option is used to redefine the location of the current vertex. You can define
the new location using any of the coordinate systems or you can directly select the location
on the screen, see figures.
Vertex before moving
Vertex after moving
REgen. This sub-option is used to regenerate the 3D mesh.
eXit. This sub-option is used to exit the Edit Vertex option.
Learning
Objectives
PEDIT
Options
Chapter 23 /Getting Started with 3D
•
Smooth Surface
This option is used to smoothen the surface of the 3D mesh by fitting a smooth surface, as
shown in figures. The smoothness of the surface will depend upon the SURFU and SURFV
system variables. The value of these system variables can be set between 2 and 200.
3D mesh before fitting the
smooth surface
Learning
Objectives
3D mesh after fitting the
smooth surface
PEDIT
Options
Chapter 23 /Getting Started with 3D
•
Desmooth
This option is used to remove the smooth surface that was fit on the 3D mesh using the
Smooth surface option and restore to the original mesh.
•
•
Mclose
This option is used to close the 3D
mesh in the M direction, as shown in
figures.
Learning
Objectives
3D mesh closed in M and N
direction
Nclose
This option is used to close the 3D
mesh in the N direction, as shown in
figures.
3D mesh open in M and
N direction
PEDIT
Options
Chapter 23 /Getting Started with 3D
•
Mopen
This option will be available if the 3D mesh is closed in the M direction. It is used to open
the 3D mesh in the M direction (figures).
•
Nopen
This option will be available if the 3D mesh is closed in the N direction. It is used to open
the 3D mesh in the N direction (figures).
•
Undo
This option is used to undo all the operations to the start of the PEDIT command.
•
eXit
This option is used to exit the PEDIT command.
Learning
Objectives
PEDIT
Options
Chapter 23 /Getting Started with 3D
 MODIFYING THE PROPERTIES OF THE HIDDEN LINES
When you invoke the HIDE command, by default
the hidden lines are suppressed and are not
displayed in the surface or solid models. The
properties of the hidden lines can be modified
using the Hidden Lines Settings dialog box, se
figure. To invoke this dialog box, right-click in the
drawing area and choose Options from the
shortcut menu. The Options dialog box appears.
Choose the User Preference tab and then choose
the Hidden Line Settings button.
• Obscured lines Area
• Face intersections Area
• Halo gap percentage Area
• Hide precision Area
Learning
Objectives
• Include text in HIDE operations
Hidden Line Settings dialog box
Chapter 23 /Getting Started with 3D
• Obscured lines Area
The options in this area are used to set the linetype and color of the hidden lines (also
called obscured lines).
•
Linetype
The Linetype drop-down list is used to set the linetype for the obscured lines. You can
select the desired linetype from this drop-down list. The linetype of the hidden lines
can also be modified using the OBSCUREDLTYPE system variable. The default value
of this variable is 0. As a result, the hidden lines are suppressed when you invoke the
HIDE command. The following table gives the details of different values of this system
variable and their corresponding linetypes that will be assigned to the hidden lines.
Figure (a) shows a model with hidden linetype changed to dashed and figure (b)
shows the same model with hidden lines changed to dotted.
Learning
Objectives
Hidden Lines Settings
Dialog Box
Chapter 23 /Getting Started with 3D
Different value of system variable and their
corresponding linetype
Learning
Objectives
Linetype
Chapter 23 /Getting Started with 3D
Figure (a) Model with hidden lines
changed to dashed
Learning
Objectives
Figure (b) Model with hidden lines
changed to dashed
Linetype
Chapter 23 /Getting Started with 3D
•
Color
The Color drop-down list is used to define color for the obscured lines. If you define a
separate color, the hidden lines will be displayed with that color when you invoke the HIDE
command. You can select the required color from this drop-down list. This can also be
done using the OBSCUREDCOLOR system variable. Using this variable, you can define
the color that you want to assign to the hidden lines. The default value of this variable is
257. This value corresponds to the By Entity color. You can enter the number of any
desired color at the sequence that will follow when you enter this system variable. For
example, if you set the value of the OBSCUREDLTYPE variable to 2 and that of the
OBSCUREDCOLOR to 1, the hidden lines will appear in red dashed lines when you invoke
the HIDE command.
Learning
Objectives
Obscured
Lines Area
Chapter 23 /Getting Started with 3D
• Face intersections Area
The options in the Face intersections area are used to display a 3D curve at the
intersection of two surfaces. These options are discussed next.
•
Display intersections
If the Display intersections check box is selected, a 3D curve will be displayed that
will define the intersecting portion of the 3D surfaces or solid models.
•
Color
The Color drop-down list is used to specify the color of the 3D curve that is displayed
at the intersection of 3D surfaces or solid models.
Learning
Objectives
Hidden Lines Settings
Dialog Box
Chapter 23 /Getting Started with 3D
• Halo gap percentage Area
The Halo gap percentage area is used to specify in terms of percentage the distance by
which the lines that lie behind a surface or solid model will be shortened, see figures.
Hiding the lines with halo
gap percentage as 0
Learning
Objectives
Hiding the lines with halo
gap percentage as 40
Hidden Lines Settings
Dialog Box
Chapter 23 /Getting Started with 3D
• Hide precision Area
The Hide precision area is used to define the precision of the hidden lines. You can
select the Low (single) radio button to set the hide precision to single. Similarly, you can
select the hide precision to double by selecting the High (double) radio button.
• Include text in HIDE operations
The Include text in HIDE operations check box is selected to hide the text that lies
behind a surface or solid model when the HIDE command is invoked. If this check box is
cleared, the text will not be hidden, even if lies behind a surface or a solid model.
Learning
Objectives
Text included while
hiding the hidden lines
Text excluded while
hiding the hidden lines
Hidden Lines Settings
Dialog Box
Chapter 23 /Getting Started with 3D
 Exercise 4 and 5
In these exercises you will create the models shown in the figures. Assume the missing
dimensions for the models.
Model for Exercise 4
Learning
Objectives
Model for Exercise 5
Chapter 23 /Getting Started with 3D
 Exercise 6
In this exercise you will create the model as shown
in the figure. Assume the missing dimensions for
the model.
Model for Exercise 6
Learning
Objectives
Chapter 23 /Getting Started with 3D
 Problem Solving Exercise 1
Create the drawing shown in figure.
The transition at the bottom can be
drawn by using
the EDGESURF
command. The edges consist of the
semicircle at the top, half rectangle at
the bottom, and the two lines joining
the endpoints of the semicircle to the
endpoints of the bottom rectangle. The
angle of the side tubes are 90- and 45degrees.
Problem Solving Exercise 1
Learning
Objectives
Chapter 23 /Getting Started with 3D
 Problem Solving Exercise 2
Create the drawing shown in figure.
First, create one of the segments of the
base and then use the ARRAY
command to complete the base.
Problem Solving Exercise 2
Learning
Objectives
Chapter 23 /Getting Started with 3D
 Problem Solving Exercise 3
Create the drawing shown in figure. First,
create the base unit (transition) and then the
dish and cone.
Problem Solving Exercise 3
Learning
Objectives
Chapter 23 /Getting Started with 3D
 Problem Solving Exercise 4
Create the drawing shown in figure. First,
create one of the transitions and use the
mirror command to get the second
transition. To get the circular sections, draw
circles and then create a surface between
the circles.
Problem Solving Exercise 4
Learning
Objectives