Working with Three Dimensional Drawing

7. Working with Three Dimensional Drawing

Introduction

Although there are sufficient number of commands to create special 3-Dimensional objects, a lot can be obtained by altering the properties of basic 2-Dimensional objects such as polylines. There are many objects in 2D drawings that can be converted to 3D by providing a thickness by using the 'THICKNESS' option in the Properties 'DDCHPROP' command. The 2D objects that are modified to 3D with a thickness command are also said to be extruded. But you should not be confused with this EXTRUDE command as a THICKNESS command. These two are different commands. The 'EXTRUDE' command creates solid extrusions whereas, the 'THICKNESS' command creates a surface extrusion. Besides, all the objects can be provided an elevation by moving them in Z-direction by using the 'MOVE' command. You can quickly produce simple & easy 3D drawings with a combination of the 'MOVE' & 'Properties' commands.

7.1 Wireframe, Surface and Solid Modeling

Wireframe Modeling:

Thewire-frame modelis a visual presentation of a 3-dimensionalor physical object used in3D computer graphics. It is a skeletal description of a 3-Dimensional object. There are no any surfaces in a wireframe model and it consists only of points, lines and curves that describe the edges of the drawing objects. With AutoCAD we can create wireframe models by positioning 2D (planar) objects anywhere in 3D space. AutoCAD also provides some 3-Dimensional 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, so this type of modeling can be the most time consuming.

Surfaces modeling:

Surface modeling is more refined than wireframe modeling because it defines not only the edges of a 3D object, but also its surfaces. The AutoCAD surface modeler defines the faceted surfaces using a polygonal mesh. Because the faces of the mesh being planar, the mesh can only approximate curved surfaces. With Mechanical Desktop, you can easily create true curved surfaces. In order to differentiate these two types of surfaces, AutoCAD calls faceted surfaces, meshes.

Solid Modeling:

Solid modeling is one of the easiest types of 3D modeling, compared to the above modelings. With the AutoCAD solid modeler, we can make 3D objects by creating basic 3D shapes such as cones, cylinders, spheres, wedges, and so on. Then, you can combine these shapes to create more and more complex solids by joining or subtracting them or finding their intersecting (over-lapping) volume. We can also create solids by sweeping a 2D object along a path or by revolving the object about an axis.

NOTE: Because each modeling type uses a different method for constructing 3D models and editing methods vary in their effect on the different model types, it is recommended that you do not mix the modeling methods.

7.2 Creating 3D Drawing using THICKNESS and ELEVATION Commands

THICKNESS Command:

1. Type THICKNESS in the command line

Command: THICKNESS

2. Type the thickness of the drawing object.

Enter the value for THICKNESS: (number)

Although AutoCAD has a no. of commands for creating special 3D objects, a lot can be achieved by changing the properties of basic 2D objects like polylines. Most of the 2D objects can be given a thickness using the thickness option in the 'PROPERTIES' command. Although the objects with a thickness can be said to be extruded, this should not be confused with the 'EXTRUDE' command that creates solid extrusions.

Moreover, thickness is a property of an object that provides them a 3D appearance. The 3-Dimensional thickness of an object is the distance up to where that object is thickened, above/below its location in space. Positive(+ve) thickness extrudes upward in the +ve Z-direction; negative(-ve) thickness extrudes downward -ve Z-direction. Zero thickness means that there is no 3-Dimensional thickening of any object. The Z-direction is determined by the orientation of the UCS(User Coordinate System) at the time the object is created. Objects with a non-zero thickness can be shaded & also can hide other objects behind them.

We can change the appearance of the following types of objects with this thickness property:

1. 2-Dimensional solids
2. Circles
3. Arcs
4. Traces
5. Lines
6. Polylines (including polygons, rectangles, boundaries, & donuts)

If you modify the thickness property of other types of objects, then it won't affect their appearance.

You can set the thickness property to default for newly created objects by setting the "THICKNESS" system variable. You can change the thickness of an existing object by using the Properties palette. A single object can't have different thicknesses for its different points. The 3-Dimensional thickening is applied uniformly on every drawing objects.

Perhaps, you should change the 3-Dimensional viewpoint to see the effect of 'THICKNESS' command on an object.

ELEVATION Command:

It stores the elevation for the new objects relative to the current UCS for the current space.

1. Type ELEVATION in the command line.

Command: ELEVATION

2. Draw 2 circles in the left view at the new elevation.

Note that they appear to be floating one(1) unit above the ground

7.3 Solid Modeling

• What is Solid Modeling?

- Solid modeling is the most advanced process/method of geometric modeling in 3 dimensions. Solid modeling is the representation of the solid parts of the object on the computer. The typical geometric model is made up of wire frames that show the object in the form of wires. This wire-frame structure can be 2 dimensional, 2 and a half dimensional or, 3 dimensional. Providing surface representation to the wire 3-dimensional views of geometric models makes the object appear solid on the computer screen and this is what is called a solid modeling.

• Advantages of Solid Modeling:

-It is one of the most important applications of the CAD software and lately it's been becoming increasingly popular. The solid modeling CAD(Computer Aided Design) software helps the designer to see the designed object as if it were the real manufactured product. It can be seen from various directions and in different views. This helps the designer to ensure that the object looks exactly as they wanted it to be. Besides, it also gives additional sight of vision to the designer as to what more changes can be done in the object.

7.4 Creating 3D Drawing using EXTRUDE Command

You can create solids & surfaces by extruding the selected objects. Use the 'EXTRUDE' command to create a solid/surface from a common profile of an object.

If you extrude a closed object, then the resulting object after extrusion is a solid. If you extrude an open object, then it is a surface.

Using this command you can create unique solid primitives by extruding existing 2-dimensional objects and also you can extrude multiple objects with this EXTRUDE command.

1. Type EXTRUDE in the command line.

Command: EXTRUDE

2. Pick the object to be extruded

Select objects: (pick objects)

3. Press ENTER if picking objects are completed.
4. Give the height of extrusion

Specify the height of extrusion or [Direction/Path/Taper angle]: (number)

This EXTRUDE command also creates a 3D solid or surface by extending the dimensions of an object.

1. Type EXTRUDE in the command line.

Command: EXTRUDE

2. Current wire frame density: ISOLINES= 4, Closed
3. Profiles creation mode= Surface
4. Pick the objects to extrude

Select objects to extrude or [Mode]: (pick objects)

5. Creation mode [Solid/ SUrface] : _su
6. Press ENTER after finishing to select the objects
7. Provide the height of extrusion.

` Specify height of extrusion or [Direction/Path/Taper angle/Expression] : (number)

7.5 Standard Solid Editing Commands

1. Convert to Solid:

Here, we use command 'CONVTOSOLID' in order to convert polylines & circles with thickness to 3D solids. With this 'CONVTOSOLID' command, you can convert the objects like uniform width wide polylines with thickness, circles with thickness and closed, zero width polylines with thickness into extruded 3D solids.

Type CONVTOSOLID in the command prompt

Command: convtosolid

Select objects: pick circle or polyline 1 found

Select objects: Hit ENTER

2. Convert to Surface

Here, we use the 'CONVTOSURFACE' as a command. This command converts polylines and circles with thickness to surfaces. Using 'CONVTOSURFACE' command you can convert the objects like 2D solids, Bodies, Regions, Open zero-width polylines with thickness, arcs with thickness, lines with thickness and Planar 3D faces into extruded 3D solids.

Type 'CONVTOSURFACE' in the command line

Command: CONVTOSURFACE

Select objects: 1 found

Select objects: (If finished selecting) hit ENTER.

7.5 Standard Solid Editing Commands

3D Move:

It displays the move grip tool in a 3D view and then moves objects at a specified distance.

Type 3DMOVE in the command line.

Command: 3DMOVE

Select objects: (pick object to move)

one(1) found

Select objects: hit ENTER

Specify the base point or [Displacement] : D

Specify displacement <0.000, 0.000, 0.000>: (say) 0,0,2

3D Rotate:

Type 3DROTATE in the command line

Command: 3DROTATE

Current positive angle in UCS: ANGDIR= counterclockwise

ANGBASE=0

Select objects: pick the object and hit ENTER

Specify the base point: pick point

Pick a rotation axis: select X-axis

Specify angle start point: -90

7.5 Standard Solid Editing Command

COMMAND	INPUT	DESCRIPTION
UNION	UNION/UNI	Joins two or more solids into creating one based on the total geometry at all
SUBTRACT	SUBTRACT/SU	Subtracts one or more solids from another creating a solid based on the remaining geometry.
INTERSECT	INTERSECT/IN	Creates a single solid from one more solids based on the intersected geometry.
EXTRUDE FACE	SOLIDEDIT	Allows you to increase the size of a solid by extruding out one of its faces.
SLICE	SLICE	Slices a solid along a cutting plane.
3DALIGH	3DALIGH	Aligns 3D objects in 3D space.

7.6 3D Modifying Commands: move, rotate, mirror, array

- All of the given modifying commands (Move, rotate, mirror and array) are same as in 2D. (so, look at the 2D slide)

- Extrude, rotate, offset, taper, copy, delete are editing commands.

7.7 Shading and Rendering and their Options, Motion Path Animations

The process of generating a shaded image of how geometry might look under a given set of lighting conditions, and based on a given set of materials, and it is called 'rendering'. Architects frequently provide rendered images of buildings to the customers as a part of the design process. Usually, Mechanical designers provide rendered images of components prior to producing them.

Motion Path Animations:

In short, motion path animations, such as 3D animated walk-through of a model, allow you to visually demonstrate a model to both a technical and non-technical audience. You can record and then play back a navigation to communicate your design intent dynamically.

• Topics in this section:

1. Control a Camera Motion Path
2. Specify Motion Path Settings
3. Record a Motion Path Animation

7. Working with Three Dimensional Drawing

Introduction

Although there are sufficient number of commands to create special 3-Dimensional objects, a lot can be obtained by altering the properties of basic 2-Dimensional objects such as polylines. There are many objects in 2D drawings that can be converted to 3D by providing a thickness by using the 'THICKNESS' option in the Properties 'DDCHPROP' command. The 2D objects that are modified to 3D with a thickness command are also said to be extruded. But you should not be confused with this EXTRUDE command as a THICKNESS command. These two are different commands. The 'EXTRUDE' command creates solid extrusions whereas, the 'THICKNESS' command creates a surface extrusion. Besides, all the objects can be provided an elevation by moving them in Z-direction by using the 'MOVE' command. You can quickly produce simple & easy 3D drawings with a combination of the 'MOVE' & 'Properties' commands.

7.1 Wireframe, Surface and Solid Modeling

Wireframe Modeling:

Thewire-frame modelis a visual presentation of a 3-dimensionalor physical object used in3D computer graphics. It is a skeletal description of a 3-Dimensional object. There are no any surfaces in a wireframe model and it consists only of points, lines and curves that describe the edges of the drawing objects. With AutoCAD we can create wireframe models by positioning 2D (planar) objects anywhere in 3D space. AutoCAD also provides some 3-Dimensional 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, so this type of modeling can be the most time consuming.

Surfaces modeling:

Surface modeling is more refined than wireframe modeling because it defines not only the edges of a 3D object, but also its surfaces. The AutoCAD surface modeler defines the faceted surfaces using a polygonal mesh. Because the faces of the mesh being planar, the mesh can only approximate curved surfaces. With Mechanical Desktop, you can easily create true curved surfaces. In order to differentiate these two types of surfaces, AutoCAD calls faceted surfaces, meshes.

Solid Modeling:

Solid modeling is one of the easiest types of 3D modeling, compared to the above modelings. With the AutoCAD solid modeler, we can make 3D objects by creating basic 3D shapes such as cones, cylinders, spheres, wedges, and so on. Then, you can combine these shapes to create more and more complex solids by joining or subtracting them or finding their intersecting (over-lapping) volume. We can also create solids by sweeping a 2D object along a path or by revolving the object about an axis.

NOTE: Because each modeling type uses a different method for constructing 3D models and editing methods vary in their effect on the different model types, it is recommended that you do not mix the modeling methods.

7.2 Creating 3D Drawing using THICKNESS and ELEVATION Commands

THICKNESS Command:

1. Type THICKNESS in the command line

Command: THICKNESS

2. Type the thickness of the drawing object.

Enter the value for THICKNESS: (number)

Although AutoCAD has a no. of commands for creating special 3D objects, a lot can be achieved by changing the properties of basic 2D objects like polylines. Most of the 2D objects can be given a thickness using the thickness option in the 'PROPERTIES' command. Although the objects with a thickness can be said to be extruded, this should not be confused with the 'EXTRUDE' command that creates solid extrusions.

Moreover, thickness is a property of an object that provides them a 3D appearance. The 3-Dimensional thickness of an object is the distance up to where that object is thickened, above/below its location in space. Positive(+ve) thickness extrudes upward in the +ve Z-direction; negative(-ve) thickness extrudes downward -ve Z-direction. Zero thickness means that there is no 3-Dimensional thickening of any object. The Z-direction is determined by the orientation of the UCS(User Coordinate System) at the time the object is created. Objects with a non-zero thickness can be shaded & also can hide other objects behind them.

We can change the appearance of the following types of objects with this thickness property:

1. 2-Dimensional solids
2. Circles
3. Arcs
4. Traces
5. Lines
6. Polylines (including polygons, rectangles, boundaries, & donuts)

If you modify the thickness property of other types of objects, then it won't affect their appearance.

You can set the thickness property to default for newly created objects by setting the "THICKNESS" system variable. You can change the thickness of an existing object by using the Properties palette. A single object can't have different thicknesses for its different points. The 3-Dimensional thickening is applied uniformly on every drawing objects.

Perhaps, you should change the 3-Dimensional viewpoint to see the effect of 'THICKNESS' command on an object.

ELEVATION Command:

It stores the elevation for the new objects relative to the current UCS for the current space.

1. Type ELEVATION in the command line.

Command: ELEVATION

2. Draw 2 circles in the left view at the new elevation.

Note that they appear to be floating one(1) unit above the ground

7.3 Solid Modeling

• What is Solid Modeling?

- Solid modeling is the most advanced process/method of geometric modeling in 3 dimensions. Solid modeling is the representation of the solid parts of the object on the computer. The typical geometric model is made up of wire frames that show the object in the form of wires. This wire-frame structure can be 2 dimensional, 2 and a half dimensional or, 3 dimensional. Providing surface representation to the wire 3-dimensional views of geometric models makes the object appear solid on the computer screen and this is what is called a solid modeling.

• Advantages of Solid Modeling:

-It is one of the most important applications of the CAD software and lately it's been becoming increasingly popular. The solid modeling CAD(Computer Aided Design) software helps the designer to see the designed object as if it were the real manufactured product. It can be seen from various directions and in different views. This helps the designer to ensure that the object looks exactly as they wanted it to be. Besides, it also gives additional sight of vision to the designer as to what more changes can be done in the object.

7.4 Creating 3D Drawing using EXTRUDE Command

You can create solids & surfaces by extruding the selected objects. Use the 'EXTRUDE' command to create a solid/surface from a common profile of an object.

If you extrude a closed object, then the resulting object after extrusion is a solid. If you extrude an open object, then it is a surface.

Using this command you can create unique solid primitives by extruding existing 2-dimensional objects and also you can extrude multiple objects with this EXTRUDE command.

1. Type EXTRUDE in the command line.

Command: EXTRUDE

2. Pick the object to be extruded

Select objects: (pick objects)

3. Press ENTER if picking objects are completed.
4. Give the height of extrusion

Specify the height of extrusion or [Direction/Path/Taper angle]: (number)

This EXTRUDE command also creates a 3D solid or surface by extending the dimensions of an object.

1. Type EXTRUDE in the command line.

Command: EXTRUDE

2. Current wire frame density: ISOLINES= 4, Closed
3. Profiles creation mode= Surface
4. Pick the objects to extrude

Select objects to extrude or [Mode]: (pick objects)

5. Creation mode [Solid/ SUrface] : _su
6. Press ENTER after finishing to select the objects
7. Provide the height of extrusion.

` Specify height of extrusion or [Direction/Path/Taper angle/Expression] : (number)

7.5 Standard Solid Editing Commands

1. Convert to Solid:

Here, we use command 'CONVTOSOLID' in order to convert polylines & circles with thickness to 3D solids. With this 'CONVTOSOLID' command, you can convert the objects like uniform width wide polylines with thickness, circles with thickness and closed, zero width polylines with thickness into extruded 3D solids.

Type CONVTOSOLID in the command prompt

Command: convtosolid

Select objects: pick circle or polyline 1 found

Select objects: Hit ENTER

2. Convert to Surface

Here, we use the 'CONVTOSURFACE' as a command. This command converts polylines and circles with thickness to surfaces. Using 'CONVTOSURFACE' command you can convert the objects like 2D solids, Bodies, Regions, Open zero-width polylines with thickness, arcs with thickness, lines with thickness and Planar 3D faces into extruded 3D solids.

Type 'CONVTOSURFACE' in the command line

Command: CONVTOSURFACE

Select objects: 1 found

Select objects: (If finished selecting) hit ENTER.

7.5 Standard Solid Editing Commands

3D Move:

It displays the move grip tool in a 3D view and then moves objects at a specified distance.

Type 3DMOVE in the command line.

Command: 3DMOVE

Select objects: (pick object to move)

one(1) found

Select objects: hit ENTER

Specify the base point or [Displacement] : D

Specify displacement <0.000, 0.000, 0.000>: (say) 0,0,2

3D Rotate:

Type 3DROTATE in the command line

Command: 3DROTATE

Current positive angle in UCS: ANGDIR= counterclockwise

ANGBASE=0

Select objects: pick the object and hit ENTER

Specify the base point: pick point

Pick a rotation axis: select X-axis

Specify angle start point: -90

7.5 Standard Solid Editing Command

COMMAND	INPUT	DESCRIPTION
UNION	UNION/UNI	Joins two or more solids into creating one based on the total geometry at all
SUBTRACT	SUBTRACT/SU	Subtracts one or more solids from another creating a solid based on the remaining geometry.
INTERSECT	INTERSECT/IN	Creates a single solid from one more solids based on the intersected geometry.
EXTRUDE FACE	SOLIDEDIT	Allows you to increase the size of a solid by extruding out one of its faces.
SLICE	SLICE	Slices a solid along a cutting plane.
3DALIGH	3DALIGH	Aligns 3D objects in 3D space.

7.6 3D Modifying Commands: move, rotate, mirror, array

- All of the given modifying commands (Move, rotate, mirror and array) are same as in 2D. (so, look at the 2D slide)

- Extrude, rotate, offset, taper, copy, delete are editing commands.

7.7 Shading and Rendering and their Options, Motion Path Animations

The process of generating a shaded image of how geometry might look under a given set of lighting conditions, and based on a given set of materials, and it is called 'rendering'. Architects frequently provide rendered images of buildings to the customers as a part of the design process. Usually, Mechanical designers provide rendered images of components prior to producing them.

Motion Path Animations:

In short, motion path animations, such as 3D animated walk-through of a model, allow you to visually demonstrate a model to both a technical and non-technical audience. You can record and then play back a navigation to communicate your design intent dynamically.

• Topics in this section:

1. Control a Camera Motion Path
2. Specify Motion Path Settings
3. Record a Motion Path Animation

7. Working with Three Dimensional Drawing

Introduction

Although there are sufficient number of commands to create special 3-Dimensional objects, a lot can be obtained by altering the properties of basic 2-Dimensional objects such as polylines. There are many objects in 2D drawings that can be converted to 3D by providing a thickness by using the 'THICKNESS' option in the Properties 'DDCHPROP' command. The 2D objects that are modified to 3D with a thickness command are also said to be extruded. But you should not be confused with this EXTRUDE command as a THICKNESS command. These two are different commands. The 'EXTRUDE' command creates solid extrusions whereas, the 'THICKNESS' command creates a surface extrusion. Besides, all the objects can be provided an elevation by moving them in Z-direction by using the 'MOVE' command. You can quickly produce simple & easy 3D drawings with a combination of the 'MOVE' & 'Properties' commands.

7.1 Wireframe, Surface and Solid Modeling

Wireframe Modeling:

Thewire-frame modelis a visual presentation of a 3-dimensionalor physical object used in3D computer graphics. It is a skeletal description of a 3-Dimensional object. There are no any surfaces in a wireframe model and it consists only of points, lines and curves that describe the edges of the drawing objects. With AutoCAD we can create wireframe models by positioning 2D (planar) objects anywhere in 3D space. AutoCAD also provides some 3-Dimensional 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, so this type of modeling can be the most time consuming.

Surfaces modeling:

Surface modeling is more refined than wireframe modeling because it defines not only the edges of a 3D object, but also its surfaces. The AutoCAD surface modeler defines the faceted surfaces using a polygonal mesh. Because the faces of the mesh being planar, the mesh can only approximate curved surfaces. With Mechanical Desktop, you can easily create true curved surfaces. In order to differentiate these two types of surfaces, AutoCAD calls faceted surfaces, meshes.

Solid Modeling:

Solid modeling is one of the easiest types of 3D modeling, compared to the above modelings. With the AutoCAD solid modeler, we can make 3D objects by creating basic 3D shapes such as cones, cylinders, spheres, wedges, and so on. Then, you can combine these shapes to create more and more complex solids by joining or subtracting them or finding their intersecting (over-lapping) volume. We can also create solids by sweeping a 2D object along a path or by revolving the object about an axis.

NOTE: Because each modeling type uses a different method for constructing 3D models and editing methods vary in their effect on the different model types, it is recommended that you do not mix the modeling methods.

7.2 Creating 3D Drawing using THICKNESS and ELEVATION Commands

THICKNESS Command:

1. Type THICKNESS in the command line

Command: THICKNESS

2. Type the thickness of the drawing object.

Enter the value for THICKNESS: (number)

Although AutoCAD has a no. of commands for creating special 3D objects, a lot can be achieved by changing the properties of basic 2D objects like polylines. Most of the 2D objects can be given a thickness using the thickness option in the 'PROPERTIES' command. Although the objects with a thickness can be said to be extruded, this should not be confused with the 'EXTRUDE' command that creates solid extrusions.

Moreover, thickness is a property of an object that provides them a 3D appearance. The 3-Dimensional thickness of an object is the distance up to where that object is thickened, above/below its location in space. Positive(+ve) thickness extrudes upward in the +ve Z-direction; negative(-ve) thickness extrudes downward -ve Z-direction. Zero thickness means that there is no 3-Dimensional thickening of any object. The Z-direction is determined by the orientation of the UCS(User Coordinate System) at the time the object is created. Objects with a non-zero thickness can be shaded & also can hide other objects behind them.

We can change the appearance of the following types of objects with this thickness property:

1. 2-Dimensional solids
2. Circles
3. Arcs
4. Traces
5. Lines
6. Polylines (including polygons, rectangles, boundaries, & donuts)

If you modify the thickness property of other types of objects, then it won't affect their appearance.

You can set the thickness property to default for newly created objects by setting the "THICKNESS" system variable. You can change the thickness of an existing object by using the Properties palette. A single object can't have different thicknesses for its different points. The 3-Dimensional thickening is applied uniformly on every drawing objects.

Perhaps, you should change the 3-Dimensional viewpoint to see the effect of 'THICKNESS' command on an object.

ELEVATION Command:

It stores the elevation for the new objects relative to the current UCS for the current space.

1. Type ELEVATION in the command line.

Command: ELEVATION

2. Draw 2 circles in the left view at the new elevation.

Note that they appear to be floating one(1) unit above the ground

7.3 Solid Modeling

• What is Solid Modeling?

- Solid modeling is the most advanced process/method of geometric modeling in 3 dimensions. Solid modeling is the representation of the solid parts of the object on the computer. The typical geometric model is made up of wire frames that show the object in the form of wires. This wire-frame structure can be 2 dimensional, 2 and a half dimensional or, 3 dimensional. Providing surface representation to the wire 3-dimensional views of geometric models makes the object appear solid on the computer screen and this is what is called a solid modeling.

• Advantages of Solid Modeling:

-It is one of the most important applications of the CAD software and lately it's been becoming increasingly popular. The solid modeling CAD(Computer Aided Design) software helps the designer to see the designed object as if it were the real manufactured product. It can be seen from various directions and in different views. This helps the designer to ensure that the object looks exactly as they wanted it to be. Besides, it also gives additional sight of vision to the designer as to what more changes can be done in the object.

7.4 Creating 3D Drawing using EXTRUDE Command

You can create solids & surfaces by extruding the selected objects. Use the 'EXTRUDE' command to create a solid/surface from a common profile of an object.

If you extrude a closed object, then the resulting object after extrusion is a solid. If you extrude an open object, then it is a surface.

Using this command you can create unique solid primitives by extruding existing 2-dimensional objects and also you can extrude multiple objects with this EXTRUDE command.

1. Type EXTRUDE in the command line.

Command: EXTRUDE

2. Pick the object to be extruded

Select objects: (pick objects)

3. Press ENTER if picking objects are completed.
4. Give the height of extrusion

Specify the height of extrusion or [Direction/Path/Taper angle]: (number)

This EXTRUDE command also creates a 3D solid or surface by extending the dimensions of an object.

1. Type EXTRUDE in the command line.

Command: EXTRUDE

2. Current wire frame density: ISOLINES= 4, Closed
3. Profiles creation mode= Surface
4. Pick the objects to extrude

Select objects to extrude or [Mode]: (pick objects)

5. Creation mode [Solid/ SUrface] : _su
6. Press ENTER after finishing to select the objects
7. Provide the height of extrusion.

` Specify height of extrusion or [Direction/Path/Taper angle/Expression] : (number)

7.5 Standard Solid Editing Commands

1. Convert to Solid:

Here, we use command 'CONVTOSOLID' in order to convert polylines & circles with thickness to 3D solids. With this 'CONVTOSOLID' command, you can convert the objects like uniform width wide polylines with thickness, circles with thickness and closed, zero width polylines with thickness into extruded 3D solids.

Type CONVTOSOLID in the command prompt

Command: convtosolid

Select objects: pick circle or polyline 1 found

Select objects: Hit ENTER

2. Convert to Surface

Here, we use the 'CONVTOSURFACE' as a command. This command converts polylines and circles with thickness to surfaces. Using 'CONVTOSURFACE' command you can convert the objects like 2D solids, Bodies, Regions, Open zero-width polylines with thickness, arcs with thickness, lines with thickness and Planar 3D faces into extruded 3D solids.

Type 'CONVTOSURFACE' in the command line

Command: CONVTOSURFACE

Select objects: 1 found

Select objects: (If finished selecting) hit ENTER.

7.5 Standard Solid Editing Commands

3D Move:

It displays the move grip tool in a 3D view and then moves objects at a specified distance.

Type 3DMOVE in the command line.

Command: 3DMOVE

Select objects: (pick object to move)

one(1) found

Select objects: hit ENTER

Specify the base point or [Displacement] : D

Specify displacement <0.000, 0.000, 0.000>: (say) 0,0,2

3D Rotate:

Type 3DROTATE in the command line

Command: 3DROTATE

Current positive angle in UCS: ANGDIR= counterclockwise

ANGBASE=0

Select objects: pick the object and hit ENTER

Specify the base point: pick point

Pick a rotation axis: select X-axis

Specify angle start point: -90

7.5 Standard Solid Editing Command

COMMAND	INPUT	DESCRIPTION
UNION	UNION/UNI	Joins two or more solids into creating one based on the total geometry at all
SUBTRACT	SUBTRACT/SU	Subtracts one or more solids from another creating a solid based on the remaining geometry.
INTERSECT	INTERSECT/IN	Creates a single solid from one more solids based on the intersected geometry.
EXTRUDE FACE	SOLIDEDIT	Allows you to increase the size of a solid by extruding out one of its faces.
SLICE	SLICE	Slices a solid along a cutting plane.
3DALIGH	3DALIGH	Aligns 3D objects in 3D space.

7.6 3D Modifying Commands: move, rotate, mirror, array

- All of the given modifying commands (Move, rotate, mirror and array) are same as in 2D. (so, look at the 2D slide)

- Extrude, rotate, offset, taper, copy, delete are editing commands.

7.7 Shading and Rendering and their Options, Motion Path Animations

The process of generating a shaded image of how geometry might look under a given set of lighting conditions, and based on a given set of materials, and it is called 'rendering'. Architects frequently provide rendered images of buildings to the customers as a part of the design process. Usually, Mechanical designers provide rendered images of components prior to producing them.

Motion Path Animations:

In short, motion path animations, such as 3D animated walk-through of a model, allow you to visually demonstrate a model to both a technical and non-technical audience. You can record and then play back a navigation to communicate your design intent dynamically.

• Topics in this section:

1. Control a Camera Motion Path
2. Specify Motion Path Settings
3. Record a Motion Path Animation

7. Working with Three Dimensional Drawing

Introduction

Although there are sufficient number of commands to create special 3-Dimensional objects, a lot can be obtained by altering the properties of basic 2-Dimensional objects such as polylines. There are many objects in 2D drawings that can be converted to 3D by providing a thickness by using the 'THICKNESS' option in the Properties 'DDCHPROP' command. The 2D objects that are modified to 3D with a thickness command are also said to be extruded. But you should not be confused with this EXTRUDE command as a THICKNESS command. These two are different commands. The 'EXTRUDE' command creates solid extrusions whereas, the 'THICKNESS' command creates a surface extrusion. Besides, all the objects can be provided an elevation by moving them in Z-direction by using the 'MOVE' command. You can quickly produce simple & easy 3D drawings with a combination of the 'MOVE' & 'Properties' commands.

7.1 Wireframe, Surface and Solid Modeling

Wireframe Modeling:

Thewire-frame modelis a visual presentation of a 3-dimensionalor physical object used in3D computer graphics. It is a skeletal description of a 3-Dimensional object. There are no any surfaces in a wireframe model and it consists only of points, lines and curves that describe the edges of the drawing objects. With AutoCAD we can create wireframe models by positioning 2D (planar) objects anywhere in 3D space. AutoCAD also provides some 3-Dimensional 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, so this type of modeling can be the most time consuming.

Surfaces modeling:

Surface modeling is more refined than wireframe modeling because it defines not only the edges of a 3D object, but also its surfaces. The AutoCAD surface modeler defines the faceted surfaces using a polygonal mesh. Because the faces of the mesh being planar, the mesh can only approximate curved surfaces. With Mechanical Desktop, you can easily create true curved surfaces. In order to differentiate these two types of surfaces, AutoCAD calls faceted surfaces, meshes.

Solid Modeling:

Solid modeling is one of the easiest types of 3D modeling, compared to the above modelings. With the AutoCAD solid modeler, we can make 3D objects by creating basic 3D shapes such as cones, cylinders, spheres, wedges, and so on. Then, you can combine these shapes to create more and more complex solids by joining or subtracting them or finding their intersecting (over-lapping) volume. We can also create solids by sweeping a 2D object along a path or by revolving the object about an axis.

NOTE: Because each modeling type uses a different method for constructing 3D models and editing methods vary in their effect on the different model types, it is recommended that you do not mix the modeling methods.

7.2 Creating 3D Drawing using THICKNESS and ELEVATION Commands

THICKNESS Command:

1. Type THICKNESS in the command line

Command: THICKNESS

2. Type the thickness of the drawing object.

Enter the value for THICKNESS: (number)

Although AutoCAD has a no. of commands for creating special 3D objects, a lot can be achieved by changing the properties of basic 2D objects like polylines. Most of the 2D objects can be given a thickness using the thickness option in the 'PROPERTIES' command. Although the objects with a thickness can be said to be extruded, this should not be confused with the 'EXTRUDE' command that creates solid extrusions.

Moreover, thickness is a property of an object that provides them a 3D appearance. The 3-Dimensional thickness of an object is the distance up to where that object is thickened, above/below its location in space. Positive(+ve) thickness extrudes upward in the +ve Z-direction; negative(-ve) thickness extrudes downward -ve Z-direction. Zero thickness means that there is no 3-Dimensional thickening of any object. The Z-direction is determined by the orientation of the UCS(User Coordinate System) at the time the object is created. Objects with a non-zero thickness can be shaded & also can hide other objects behind them.

We can change the appearance of the following types of objects with this thickness property:

1. 2-Dimensional solids
2. Circles
3. Arcs
4. Traces
5. Lines
6. Polylines (including polygons, rectangles, boundaries, & donuts)

If you modify the thickness property of other types of objects, then it won't affect their appearance.

You can set the thickness property to default for newly created objects by setting the "THICKNESS" system variable. You can change the thickness of an existing object by using the Properties palette. A single object can't have different thicknesses for its different points. The 3-Dimensional thickening is applied uniformly on every drawing objects.

Perhaps, you should change the 3-Dimensional viewpoint to see the effect of 'THICKNESS' command on an object.

ELEVATION Command:

It stores the elevation for the new objects relative to the current UCS for the current space.

1. Type ELEVATION in the command line.

Command: ELEVATION

2. Draw 2 circles in the left view at the new elevation.

Note that they appear to be floating one(1) unit above the ground

7.3 Solid Modeling

• What is Solid Modeling?

- Solid modeling is the most advanced process/method of geometric modeling in 3 dimensions. Solid modeling is the representation of the solid parts of the object on the computer. The typical geometric model is made up of wire frames that show the object in the form of wires. This wire-frame structure can be 2 dimensional, 2 and a half dimensional or, 3 dimensional. Providing surface representation to the wire 3-dimensional views of geometric models makes the object appear solid on the computer screen and this is what is called a solid modeling.

• Advantages of Solid Modeling:

-It is one of the most important applications of the CAD software and lately it's been becoming increasingly popular. The solid modeling CAD(Computer Aided Design) software helps the designer to see the designed object as if it were the real manufactured product. It can be seen from various directions and in different views. This helps the designer to ensure that the object looks exactly as they wanted it to be. Besides, it also gives additional sight of vision to the designer as to what more changes can be done in the object.

7.4 Creating 3D Drawing using EXTRUDE Command

You can create solids & surfaces by extruding the selected objects. Use the 'EXTRUDE' command to create a solid/surface from a common profile of an object.

If you extrude a closed object, then the resulting object after extrusion is a solid. If you extrude an open object, then it is a surface.

Using this command you can create unique solid primitives by extruding existing 2-dimensional objects and also you can extrude multiple objects with this EXTRUDE command.

1. Type EXTRUDE in the command line.

Command: EXTRUDE

2. Pick the object to be extruded

Select objects: (pick objects)

3. Press ENTER if picking objects are completed.
4. Give the height of extrusion

Specify the height of extrusion or [Direction/Path/Taper angle]: (number)

This EXTRUDE command also creates a 3D solid or surface by extending the dimensions of an object.

1. Type EXTRUDE in the command line.

Command: EXTRUDE

2. Current wire frame density: ISOLINES= 4, Closed
3. Profiles creation mode= Surface
4. Pick the objects to extrude

Select objects to extrude or [Mode]: (pick objects)

5. Creation mode [Solid/ SUrface] : _su
6. Press ENTER after finishing to select the objects
7. Provide the height of extrusion.

` Specify height of extrusion or [Direction/Path/Taper angle/Expression] : (number)

7.5 Standard Solid Editing Commands

1. Convert to Solid:

Here, we use command 'CONVTOSOLID' in order to convert polylines & circles with thickness to 3D solids. With this 'CONVTOSOLID' command, you can convert the objects like uniform width wide polylines with thickness, circles with thickness and closed, zero width polylines with thickness into extruded 3D solids.

Type CONVTOSOLID in the command prompt

Command: convtosolid

Select objects: pick circle or polyline 1 found

Select objects: Hit ENTER

2. Convert to Surface

Here, we use the 'CONVTOSURFACE' as a command. This command converts polylines and circles with thickness to surfaces. Using 'CONVTOSURFACE' command you can convert the objects like 2D solids, Bodies, Regions, Open zero-width polylines with thickness, arcs with thickness, lines with thickness and Planar 3D faces into extruded 3D solids.

Type 'CONVTOSURFACE' in the command line

Command: CONVTOSURFACE

Select objects: 1 found

Select objects: (If finished selecting) hit ENTER.

7.5 Standard Solid Editing Commands

3D Move:

It displays the move grip tool in a 3D view and then moves objects at a specified distance.

Type 3DMOVE in the command line.

Command: 3DMOVE

Select objects: (pick object to move)

one(1) found

Select objects: hit ENTER

Specify the base point or [Displacement] : D

Specify displacement <0.000, 0.000, 0.000>: (say) 0,0,2

3D Rotate:

Type 3DROTATE in the command line

Command: 3DROTATE

Current positive angle in UCS: ANGDIR= counterclockwise

ANGBASE=0

Select objects: pick the object and hit ENTER

Specify the base point: pick point

Pick a rotation axis: select X-axis

Specify angle start point: -90

7.5 Standard Solid Editing Command

COMMAND	INPUT	DESCRIPTION
UNION	UNION/UNI	Joins two or more solids into creating one based on the total geometry at all
SUBTRACT	SUBTRACT/SU	Subtracts one or more solids from another creating a solid based on the remaining geometry.
INTERSECT	INTERSECT/IN	Creates a single solid from one more solids based on the intersected geometry.
EXTRUDE FACE	SOLIDEDIT	Allows you to increase the size of a solid by extruding out one of its faces.
SLICE	SLICE	Slices a solid along a cutting plane.
3DALIGH	3DALIGH	Aligns 3D objects in 3D space.

7.6 3D Modifying Commands: move, rotate, mirror, array

- All of the given modifying commands (Move, rotate, mirror and array) are same as in 2D. (so, look at the 2D slide)

- Extrude, rotate, offset, taper, copy, delete are editing commands.

7.7 Shading and Rendering and their Options, Motion Path Animations

The process of generating a shaded image of how geometry might look under a given set of lighting conditions, and based on a given set of materials, and it is called 'rendering'. Architects frequently provide rendered images of buildings to the customers as a part of the design process. Usually, Mechanical designers provide rendered images of components prior to producing them.

Motion Path Animations:

In short, motion path animations, such as 3D animated walk-through of a model, allow you to visually demonstrate a model to both a technical and non-technical audience. You can record and then play back a navigation to communicate your design intent dynamically.

• Topics in this section:

1. Control a Camera Motion Path
2. Specify Motion Path Settings
3. Record a Motion Path Animation