LECTURE-II
Creating the Geometry
The symbols associated with each of the Geometry subpad command sets are as follows.
Symbol
Command Set
Vertex
Edge
Face
Volume
Group
If you create an entity or coordinate system without specifying a label, GAMBIT
automatically assigns a label to the entity. The automatically assigned label consists of a
name representing the entity type followed by a decimal point and an integer-for
example, volume.6. Automatically assigned labels for virtual and faceted entities are
preceded by the characters "v_" and "f_"-for example, v_volume.6 and f_edge.12.
The integer that GAMBIT assigns to automatically labeled entity names is equal to n+1,
where n is the highest integer associated with any currently existing entity of the same
type. The value of the assigned integer is independent of whether or not the entity is real
or virtual.

If you create a real vertex in a model that already contains vertices labeled
vertex.1, vertex.2, and vertex.3, the new vertex is named vertex.4.
Specifying Individual Entities
Many of the modeling forms require you to specify individual entities-such as vertices,
edges, or faces-to which to apply the operations specified on the form. When a form
requires you to specify one or more individual entities, it contains a list box titled with
the entity type. For example, the Create Real Vertex form requires you to specify the
coordinate system with respect to which the vertex is to be positioned; therefore, it
contains a list box, titled Coordinate Sys.
Unless otherwise noted, you can specify an individual entity in one of three ways:



Input the name of the entity in the list box.
Click the pick-list button at the right side of the list box and select the entity by
means of the pick-list form.
Pick the entity from the model as displayed in the graphics window.
Specifying Multiple Entities



Input the first entity name, press Enter; and clear the list box. Input the second
entity name and press Enter again.
Click the pick-list button located at the right side of the list box and select the
entities by means of the pick-list form.
Pick a vertex or edge associated with the first entity as displayed in the graphics
window and Shift-right-click anywhere else in the graphics window to accept the
selection. Then repeat the procedure for the second entity.
Working with Coordinate Systems
Some of the GAMBIT modeling forms require you to specify a location in space relative
to a specified coordinate system. For example, the Create Real Vertex form requires you
to specify the three coordinates describing the point at which the vertex is to be created.
To specify the location of a point, you must specify the following information:


The reference coordinate system (global or local)
Three coordinate parameters that describe the point relative to the specified
reference system
Specifying Reference Coordinate Systems
You can specify the reference coordinate system in one of three ways:

Input the name of the coordinate system in the Coordinate Sys list box.


Click the pick-list button located at the right side of the Coordinate Sys list box
and select the system from the coordinate-system pick list.
Pick the coordinate system (on one of its axes) in the graphics window.
The required input parameters for each of the three types of coordinate systems are as
follows.
System Type
Parameters
GAMBIT Titles
Cartesian
x, y, z
Cylindrical
r, t, z
Spherical
r, t, p
The angle parameters, and , must be specified in degrees. They are defined such that
vectors are coincident with the x, y, and z axes of a Cartesian coordinate system when
and
, have the following values.
System
Cylindrical
Spherical
Angle
Parameter
Axis
Direction
= 0, z = 0
= 90o, z = 0
x
y
+x
+y
= 90o
z
x
+z
+x
= 0,
= 90o,
90o
=
Moving, Copying and Aligning Entities
You can change the position and/or orientation of an entity in one of two ways:


Move or copy the entity, by means of a Move/Copy form
Align the entity, by means of an Align form
Moving an Entity
Each option is accessible by means of a Move/Copy form.
Example Move/Copy form
Translating an Entity
When you translate an entity, GAMBIT repositions the entity but does not change its
orientation with respect to the reference coordinate system.
Example Move/Copy Volumes,Translate operation
To translate an entity, you must specify the following information:


The reference coordinate system
The translation parameters that define the new position of the entity relative to its
current position
Rotating an Entity
When you rotate an entity, GAMBIT repositions and reorients the entity by rotating its
vertices and edges about a specified axis.
Example Move/Copy Volumes, Rotate operation
To rotate an entity, you must specify the following information:


The axis around which the entity is to be rotated
The angle of rotation
Reflecting an Entity
When you reflect an entity, GAMBIT repositions the entity so that its vertices are
equidistant from but on opposite sides of a specified reflection plane.
Example Move/Copy Volumes: Reflect operation
To reflect an entity, you must define the plane of reflection. To define the plane of
reflection, you must specify a vector normal to the plane.
According to GAMBIT conventions, the start endpoint of the normal vector lies in the
plane and, therefore, defines the location of the plane. The end endpoint determines the
direction of the vector and, therefore, the orientation of the plane.
To specify the endpoints of the normal vector that defines the plane of reflection, you
must employ the same procedure used to specify the axis of rotation by means of the
Vector Definition form.
Scaling an Entity
When you scale an entity, GAMBIT changes the size of the entity according to a
specified scaling factor. If you specify translation parameters in addition to a scaling
factor, GAMBIT also repositions the scaled entity.
Scaling of a rectangular brick
To scale an entity, you must specify the following information:


Reference point
Scaling factor
The reference point serves as the center projection point for the scaling operation. The
scaling factor specifies the magnitude of the change in entity size.


If you specify very large scaling factors, the scaled geometry may contain gaps
between entities that are coincident with tolerance in the unscaled geometry.
If you specify very small scaling factors, the scaled geometry may be smaller than
the minimum allowable value of 10-5.
Copying Mesh Information
If you select the Copy option on any Move/Copy form (other than the Move/ Copy
Vertices form), GAMBIT displays two options at the bottom of the form:


Copy mesh linked
Copy mesh unlinked
Both options specify that any mesh information associated with the original entity is
reproduced in the copied entity. The options differ from each other only with respect to
whether or not the copied mesh is linked to the mesh on the original entity. For example,
if you copy a meshed face and select the Copy mesh linked option, GAMBIT copies the
face and its mesh and links the mesh on the copied face to that on the original face. If you
select the Copy mesh unlinked option, GAMBIT copies the face and its mesh but does
not link the original and copied meshes.
Translation Specifications
When you specify the Translate operation, the middle section of the Move/Copy form
appears. Translate specifications are as follows.
Coordinate
Sys
specifies the reference coordinate system to be used in
translating the entities.
Type
--------------------------------------
Cartesian
Cylindrical
Spherical
specifies the type of coordinate parameters to be used in
translating the entities.
Global | Local
specifies the translation parameters with respect to either the
Global or Local system.
Rotation Specifications
When you specify the Rotate operation, the middle section of the Move/Copy form
appears.
Move/Copyform, Rotate specifications
Rotate specifications are as follows.
Angle
specifies the angle of rotation.
Axis
--------------------------------------
Define
opens the Vector Definition form, which allows you to specify
a vector defining the axis of rotation.
Active
Coord. Sys.
Vector
displays the endpoint coordinates of the vector that currently
defines the axis of rotation. The displayed coordinates of the
vector are always defined in terms of the active coordinate
system.
Reflection Specifications
When you specify the Reflect operation, the middle section of the Move/Copy Vertices
form appears.
Move/Copy form, Reflect options
Reflect specifications are as follows.
Reflection
Plane
Define
Active Coord.
Sys. Vector
--------------------------------------
opens the Vector Definition form, which allows you to
specify a vector defining the plane of reflection.
displays the endpoint coordinates of the vector that currently
defines the plane of reflection. The displayed coordinates of
the vector are always defined in terms of the active coordinate
system.
Scaling Specifications
When you specify the Scale operation, the middle section of the Move/Copy Vertices
form appears.
Move/Copy form, Scale options
Scale specifications are as follows.
Factor
specifies the scaling factor to be used in scaling and translating
the entities.
Coordinate
Sys
specifies the reference coordinate system to be used in scaling
and translating the entities
Type
--------------------------------------
Cartesian
Cylindrical
Spherical
specifies the type of coordinate parameters to be used in
translating the entities.
Global |
Local
specifies the parameters that define the scaling reference point.
Copying an Entity
To copy an entity, you must specify three types of information:



The name of the entity to be copied (the "parent" entity)
The number of copies to be created
The manner in which the copies are to be repositioned and/or reoriented relative
to the parent entity
Creating a Single Copy of an Entity
When you create a single copy of an entity, GAMBIT duplicates all lower topology
associated with the entity and locates the copy according to the specifications on the
Move/Copy form. The final position and orientation of the copy is determined according
to the same procedures employed when you move an entity.
Creating Multiple Copies of an Entity
When you create multiple copies of an entity, GAMBIT positions, orients, and/or scales
the first copy relative to the parent entity and positions, orients, and scales each
subsequent copy relative to the previous copy created. For example, if you create two
copies of a rectangular brick and specify that the copies are to be translated in the x, y,
and z directions, GAMBIT translates the first copy relative to the parent brick and
translates the second copy relative to the first.
Two translated copies of a rectangular brick
Similarly, if you create two copies of a rectangular brick and specify a scaling factor of
1.5, GAMBIT creates one copy the edges of which are 1.5 times larger than those of the
parent brick and another copy the edges of which are 2.25 (= 1.5 1.5) times larger than
those of the parent brick
Aligning an Entity
To align an entity, you must specify two types of parameters:


The entity type and name
One, two, or three pairs of vertices that define the alignment
The entity type and name determine which entity is to be moved by means of the
alignment procedure. The vertex-pair specifications define the extent of the movement in
each of the three spherical coordinate directions.
General Three-Step Alignment Procedure
When GAMBIT aligns an entity, it performs the following three operations in sequence.
Step
Operation
Description
1
Translate
Change the position of the entity without affecting its
orientation relative to the global coordinate system
2
Rotate
Change the orientation of the entity by rotating it so that
vertices are collinear
3
Planealign
Change the orientation of the entity by rotating it about an
axis vector the endpoints of which are defined by two
existing vertices
Each step in the procedure is defined by a specified pair of existing vertices. The
following example illustrates the overall alignment procedure and the effect of vertexpair specification on the final position and orientation of an aligned face.
Alignment Example
Consider the two planar, nonaligned faces shown. Face face.1 is larger than face.2 and is
parallel to the y-z coordinate plane. Face face.2 is not parallel to any coordinate plane.
Two nonaligned GAMBIT faces
There are several ways to align face.2 such that it is coincident with face.1. One possible
procedure is as follows
1. Translate face.2 so that vertex.5 coincides with vertex.1 (Figure a)
2. Rotate face.2 about vertex.1 so that a straight line drawn from vertex.1 to vertex.2
coincides with a straight line drawn from vertex.5 to vertex.6 (Figure b)
3. Rotate (plane-align) face.2 about a straight line drawn from vertex.2 to vertex.1 so
that a plane defined by vertex.5, vertex.6, and vertex.7 coincides with a plane
defined by vertex.1, vertex.2, and vertex.3 (Figure c)
GAMBIT face-alignment operations
To define an alignment procedure, such as that shown in Figure, you must specify vertex
pairs that describe each step in the procedure. In GAMBIT, such vertex pairs are
specified by means of Align forms (see below).
Align Form Specifications
Each type of entity is associated with its own Align form. For example, the Align Faces
form shown is used to align face entities. The Align Vertices, Align Edges, Align Faces,
Align Volumes, and Align Groups forms differ from each other only with respect to the
type of entity being aligned.
Example Align Faces form
The pairs of vertices that define the alignment are classified on each form as
Translation, Rotation, and Plane Alignment vertex pairs. Each vertex pair consists of a
Start vertex and an End vertex. The Start vertex corresponds to the position of the entity
before it is aligned. The End vertex corresponds to the position or orientation of the
entity after the alignment operation is complete.
For example, the operation illustrated in can be defined according to the following
specifications on the Align Faces form.
Parameter
Face
Specification
face.2
Translation Vertex Pair:
Start
End
vertex.5
vertex.1
Rotation Vertex Pair:
Start
End
vertex.6
vertex.2
Plane Alignment Vertex
Pair: Start
End
vertex.8
vertex.4
In most cases, a given final configuration may be associated with more than one set of
alignment specifications. For example, there are six different sets of alignment
specifications that produce the final configuration shown in Figure d. One set of
specifications is that listed in the table above. Another set of specifications is as follows.
Parameter
Specification
Translation Vertex Pair:
Start
End
vertex.5
vertex.1
Rotation Vertex Pair:
Start
End
vertex.8
vertex.4
Plane Alignment Vertex
Pair: Start
End
vertex.6
vertex.2
Effect of Vertex-Pair Specification on Orientation
The final orientation of the aligned entities depends on which vertex pairs are used to
define each of the three steps in the alignment procedure. As an example of the effect of
vertex-pair specification on the final orientation, consider the two rectangular faces
shown. The faces are identical in shape and orientation and are labeled more generally
with respect to their vertices.
Two nonaligned rectangular faces
There are several configurations in which Face 2 may be considered to be fully aligned
with Face 1. Four such configurations are shown in Figure. The following table lists one
of the possible sets of vertex-pair specifications that result in each of the configurations
shown in Figure.
Parameter
(a)
(b)
(c)
(d)
Translation Vertex Pair:
Start
End
E
A
G
A
E
A
G
A
Rotation Vertex Pair:
Start
End
F
B
H
B
F
D
H
D
Plane Alignment Vertex
Pair: Start
End
H
D
F
D
H
B
F
B
Figure: Example alignment configurations of two faces
Scaling Aligned Entities
If the distances between the first two of the Start vertices differ from the corresponding
distances between the End vertices, GAMBIT activates the Scale option on the Align
form. The Scale option allows you to resize the aligned entity to match the distances
between the End vertices to which the entity is aligned. For example, if you select the
Scale option for the procedure illustrated, GAMBIT resizes face.2 so that the edge
defined by vertex.5 and vertex.6 is identical in length to the corresponding edge on face.1.
Each Align form includes the following specifications.
Entities
specifies the entities to be aligned. The type of entities
specified by means of the Entity list box is determined by
the nature of the current Align form. For example, on the
Align Vertices form, the Entity list box is titled "Vertices"
and specifies one or more vertices to be aligned.
Translation
Vertex Pair:
specifies the translation Start and End vertices.
Rotation Vertex
Pair:
specifies the rotation Start and End vertices.
Plane
Alignment
Vertex Pair:
specifies the plane-alignment Start and End vertices
Connected
Geometry
specifies that all geometry connected to the vertex is to be
aligned according to the specifications on the form.
Scale
specifies that all topology to which the vertex is connected
is to be scaled to match the distances between the
translation, rotation, and plane-alignment Start and End
vertices.
Vertex Commands
The following commands are available on the Geometry/Vertex subpad.
Symbol
Command
Description
Create Vertex
Creates a real vertex at any specified location,
a real or virtual vertex on an edge or face, a
virtual vertex associated with a volume, or a
real or virtual vertex at the intersection of two
edges
Slide Virtual
Vertex
Changes the position of a virtual vertex along
the edge or face upon which it was created
Connect
Vertices
Disconnect
Vertices
Connects real and/or virtual vertices;
disconnects vertices that are common to two
or more entities
Modify Vertex
Color
Modify Vertex
Label
Changes a vertex color; changes a vertex label
Move/Copy
Vertices
Align Vertices
Moves and/or copies vertices; aligns vertices
and connected geometry
Convert Vertices
Converts non-real vertices to real vertices
Summarize
Vertices
Check Vertices
Query Vertices
Total Entities
Displays vertex summary information; checks
validity of vertex topology and geometry;
opens a vertex query list; displays entity totals
Delete Vertices
Deletes real or virtual vertices
The following sections describe the purpose and operation of each of the Vertex
commands listed above.
2.2.1 Create Vertex
The Create Vertex command button allows you to perform the following operations.
Symbol
Command
Description
Create Real Vertex
Creates a real vertex at any
specified location
Create Vertex on Edge
Creates a real or virtual vertex on
an existing real edge
Create Vertex on Face
Creates a real or virtual vertex on
an existing real face
Create Virtual Vertex on
Volume
Creates a virtual vertex associated
with an existing real volume
Create Vertices At Edge
Intersections
Creates real or virtual vertices at
the intersections of two edges
Move/Copy/Align Vertices
The Move/Copy/Align Vertices command button allows you to perform two operations.
Symbol
Operation
Description
Move/Copy
Vertices
Moves and copies vertices
Align Vertices
Aligns vertices and connected geometry with
existing topological entities
Summarize/Check/Query Vertices and Total Entities
The Summarize/Check/Query Vertices and Total Entities command button lets you
perform the following operations.
Symbol
Command
Description
Summarize
Vertices
Displays vertex summary information in the
Transcript window
Check Vertices
Checks the topological and geometrical
validity of model vertices
Query Vertices
Opens the vertex query list
Total Entities
Displays in the Transcript window the total
number of entities of one or more specified
types
Edge Commands
The following commands are available on the Geometry/Edge subpad.
Symbol
Command
Description
Create Edge
Creates a real
or virtual edge
Connect Edges
Disconnect About
Real Edge
Connects real
and/or virtual
edges;
disconnects
edges that are
common to
two or more
entities
Modify Edge Color
Modify Edge Label
Changes an
edge color;
changes an
edge label
Move/Copy Edges
Align Edges
Moves and/or
copies edges;
aligns edges
and connected
geometry
Split Edge
Merge Edges
Splits or
merges edges
Convert Edges
Converts nonreal edges to
real edges
Summarize Edges
Check Edges
Query Edges
Total Edges
Displays edge
summary
information;
checks validity
of edge
topology and
geometry;
opens an edge
query list;
displays entity
totals
Delete Edges
Deletes real or
virtual edges
Face Commands
The following commands are available on the Geometry/Face subpad.
Symbol
Command
Description
Form Face
Creates a face from existing edges or
vertices
Create Face
Creates a face in one of three primitive
shapes
Boolean Operations
Unites, intersects, or subtracts faces
Connect Faces
Disconnect Faces
Connects real and virtual faces;
disconnects faces shared between entities
Modify Face Color
Modify Face Label
Changes a face color; changes a face label
Move/Copy Faces
Align Faces
Moves and/or copies faces: aligns faces
and connected geometry
Split Face
Merge Faces
(Virtual)
Collapse Face
(Virtual)
Simplify Faces
Splits faces about a face or vertices;
merges faces; collapses a face; simplifies
faces by removing dangling edges
Heal Real Faces
Convert Faces
Heals real face geometry; converts nonreal faces to real faces
Summarize Faces
Check Faces
Query Faces
Total Entities
Displays face summary information;
checks validity of topology and geometry;
opens a face query list; displays entity
totals
Delete Faces
Deletes real or virtual faces
Volume Commands
The following commands are available on the Geometry/Volume subpad.
Symbol
Command
Description
Form Volume
Creates a volume from existing faces or
edges
Create Volume
Creates a volume in one of several
primitive shapes
Boolean Operations
Unites, intersects, or subtracts volumes
Blend Volumes
Rounds and/or trims volume edges
Modify Volume
Color
Modify Volume
Label
Changes a volume color: changes a
volume label
Move/Copy
Volumes
Align Volumes
Moves and/or copies volumes; aligns
volumes and connected geometry
Split Volume
Merge Volumes
Splits or merges volumes
Heal Real Volume
Convert Volumes
Heals real volume geometry problems;
converts non-real volumes to real volumes
Summarize Volumes
Check Volumes
Query Volumes
Total Entities
Displays volume summary information;
checks validity of topology and geometry;
opens a volume query list; displays entity
totals
Delete Volumes
Deletes real or virtual volumes
Form Volume
The Form Volume command button allows you to perform the following operations.
Symbol
Operation
Description
Stitch Faces
Creates a volume from a set of existing
faces
Sweep Real Faces
Creates a volume by sweeping a face
along a specified path
Revolve Real Faces
Creates a volume by revolving a face
through a specified angle
Form Real Volume
From Wireframe
Creates a volume from a set of existing
edges
The following sections describe the procedures and specifications required to execute the
commands listed above.
Stitch Faces
The Stitch Faces command allows you to form a volume from a set of existing faces.
To form a volume by means of the Stitch Faces command, you must specify the
following information:


A set of faces that comprise the sides of the volume
The volume type
Specifying the Faces
To stitch faces to form a volume, you must specify a set of faces that constitute the sides
of the volume. The faces do not have to be planar but must possess coincident edges such
that the set defines a completely closed volume.
Specifying the Volume Type
GAMBIT allows you to form a real or virtual volume by means of the Stitch Faces
command. To form a real volume, you must specify only real faces. To form a virtual
volume, you can specify real and/or virtual faces.
If you specify the creation of a virtual volume, you can also specify a Tolerance value.
The Tolerance value allows you to form a volume from a set of faces the edges of which
are not exactly coincident with each other.
Using the Stitch Faces Form
To open the Stitch Faces form (see below), click the Stitch Faces command button on
the Geometry/Volume subpad.
The Stitch Faces form includes the following specifications.
Faces
specifies the faces to be used in forming the volume.
Type:
-------------------------
Real
specifies the creation of a real volume.
Virtual
specifies the creation of a virtual volume.
Tolerance
specifies the maximum allowable distance between "coincident"
boundary edges for the set of specified faces.
Label
specifies a label for the new volume
Sweep Real Faces
The Sweep Real Faces command allows you to form volumes by sweeping real faces
along a specified path.
To create a volume by means of the Sweep Real Faces command, you must specify the
following parameters.



Profile
Path
Type
The profile consists of a set of one or more faces to be swept. The path represents the trajectory of the sweep operation. The type defines the shape and orientation of the created
volume relative to those of the profile and path.
Specifying the Sweep Profile
The sweep profile consists of a set of one or more existing faces. GAMBIT creates a
separate volume corresponding to each face in the profile. Each type of sweep operation
possesses its own set of rules that govern whether or not a face constitutes a valid profile
component. In general, however, GAMBIT does not allow you to specify profile faces
that are parallel to the sweep path.
Specifying the Sweep Path
You can define the sweep path by means of either of the following specifications.


Edge
Vector
When you define the sweep path by specifying an edge, GAMBIT defines the path
according to the shape, length, and sense of the specified edge. You can reverse the
direction of the sweep path relative to the sense of the specified edge by means of the
Reverse option on the Sweep Edges form.
When you define the sweep path by specifying a vector, GAMBIT defines the path as a
straight line possessing the magnitude and direction of the vector. Specifying the Sweep
Type
GAMBIT provides two general types of sweep operations:


Rigid
Perpendicular
When you specify a rigid sweep, GAMBIT sweeps the profile along the entire length of
the specified path without altering the profile orientation with respect to the global
coordinate system. When you specify a perpendicular sweep, GAMBIT maintains a
constant angle between the face and the sweep path along the entire length of the path.
Performing a Rigid Sweep
When you specify a rigid sweep operation, GAMBIT projects the profile along the entire
length of the specified path without altering the size, shape, or orientation of the profile.
The shape and orientation of any volume created by means of a rigid sweep operation
depends on two factors:


The shape of the profile face and its orientation relative to the path
The shape and direction of the path
Specifying the Profile
The edges that bound the profile face(s) can be straight or curved, and the profile face
does not have to be planar. However, GAMBIT imposes the following restrictions on
profiles and paths employed in face-sweep operations:


None of the edges that bound the profile face can be parallel to the path
The face normal cannot be perpendicular to the path
Figure shows three path/profile configurations, only one of which constitutes a valid
configuration for a face-sweep operation.
Figure Allowed face configurations for sweeping a face
The validities of the configurations shown in the figure are as follows.



The configuration shown in Figure (a) is not valid, because edge AB is parallel to
the path.
The configuration shown in Figure (b) is not valid, because the normal to the face
(ABC) is perpendicular to the path at its starting point (D).
The combination shown in Figure (c) is valid, because none of its bounding edges
is parallel to the path.
Specifying the Path
The sweep path can be defined by means of either an edge or a vector. If you specify an
edge to define the path, the path can be straight or curved-depending on the shape of the
edge. If you specify a vector to define the path, the path is straight by definition.
Example Face-Sweep Operations
The figures below illustrate the results of the rigid face-sweep operation for two simple
path/profile configurations. In each case, the profile face is planar and is bounded by
three edges. The sweep paths shown in Figure are defined by a straight edge and a
circular arc edge, respectively.
Example rigid face sweep operation—straight path
Example rigid face sweep operation—curved path
Performing a Perpendicular Sweep
Overview
Perpendicular sweep operations differ from rigid sweep operations in that, for
perpendicular sweeps, the initial orientation between the profile and path is maintained
along the entire length of the sweep path. Rigid sweeps, by contrast, maintain the
orientation of the profile with respect to the global coordinate system along the sweep
path.
As an example of the difference between rigid and perpendicular sweep operations,
consider the profile and path shown in Figure (a). In this case, the profile consists of a
planar square face aligned with the y-z coordinate plane, and the path is defined by a
circular arc edge aligned with the x-y plane.
Example Rigid and Perpendicular sweep operations—curved path
The differences between the created faces can be summarized as follows.


If you perform a rigid sweep, GAMBIT maintains the orientation of the profile
with respect to the global coordinate system, thereby creating the volume shown
in Figure (b).
If you perform a perpendicular sweep with a zero draft angle (see below),
GAMBIT maintains the orientation between the path and profile and creates the
volume shown in Figure (c).
Perpendicular Sweep Methods
GAMBIT provides two options for perpendicular face-sweep operations:


Draft
Twist
The Draft option specifies a fixed angle of deviation between the path and the face
projection for the created volume. The Twist option allows you to revolve the profile
through a specified angle along the length of the path.
NOTE: In order to constitute a valid configuration for either a Draft or Twist operation,
the profile and path must meet the following conditions.


The profile must be planar.
The face normal cannot be perpendicular to the path.
Draft Option
When you create a volume by means of the draft method, GAMBIT allows you to expand
or contract the projected face by a specified angle along the path. Figure shows a
perpendicular draft sweep involving a profile and path identical to those shown in Figure
(a). In this case the draft angle is specified as +10o, therefore the profile expands as it is
swept along the profile curve.
Perpendicular face sweep—draft option, 10o draft angle
The Effect of Draft Angle
As noted above, when you perform a perpendicular face sweep operation by means of the
draft method, GAMBIT allows you to specify a draft angle for the created volume. The
draft angle represents the extent to which the swept edges of the volume are expanded or
contracted relative to those of the original profile.
Figure shows the effect of draft angle on the shape of a volume created by sweeping a
square profile along a straight path that is perpendicular to the face. In this case, the
profile face is a square, planar face aligned with the y-z plane, the path is defined by a
straight edge aligned with the x axis, and the draft angle is specified as 10o.
If you specify a positive draft angle, the profile expands along the length of the path (see
Figure (c)). If you specify a negative draft angle, the profile contracts along the length of
the path (see Figure (d)).
Perpendicular draft face sweep—effect of draft angle
The Effect of Draft Type
When you sweep a face by means of the perpendicular draft method and expand the
profile by means of a positive draft angle, GAMBIT allows you to specify the following
options for the expanded profile type:



Extended
Round
Mixed
Figure shows the effect of draft type on the shape of a volume created from a profile and
path identical to those shown in Figure (a). The Extended option expands the profile with
altering its basic shape (see Figure (a)). The Round option rounds the corners of the
expanded profile as shown in Figure (b). The Mixed option combines elements of the
Extended and Round options, as necessary, to fill gaps in the expanded profile.
Perpendicular face sweep, draft method—effect of draft type
Twist Method
When you perform a perpendicular sweep operation by means of the twist method,
GAMBIT revolves the profile through a specified angle along the length of the path. The
profile and path can be straight or curved.
As an example of the effects of the twist sweep procedure, consider the profile/path
configurations shown in Figure. In each case, the profile consists of a square planar face
aligned with the y-z plane. The paths shown in Figure (a) and (b) are defined by straight
and circular arc edges, respectively.
NOTE: When you employ a twist sweep procedure, GAMBIT twists the profile face
about the specified path—rather than projecting the path start location onto the face
surface geometry. Consequently, the results of the twist face-sweep operation depend, in
part, on the orientation and distance between the profile and path.
Figure: Twist-method face sweep—example profiles and paths
Figures below show the results of a perpendicular twist face-sweep procedure applied to
the profiles and paths shown in Figure (a) and (b), respectively. Figure shows results for
draft-angle values of +90oand +360o. Figure shows results for draft-angle values of +90o
and +180o.
Twist-method face sweep—straight path results
Twist-method face sweep—curved path results
Using the Sweep Real Faces Form
To open the Sweep Real Faces form (see below), click the Sweep Real Faces command
button on the Geometry/Volume subpad.
The Sweep Real Faces form includes the following specifications.
Faces
specifies one or more faces that constitute the sweep profile.
Path:
--------------------------------------
Edge
specifies that the path is described by the length, orientation,
and sense of an existing edge.
Edge
specifies the edge to be used as the sweep path.
Reverse
specifies that the direction of the path is reversed with respect
to the sense of the specified edge.
Vector
specifies that the path is described by a vector.
When you select the Vector option, GAMBIT displays a
command button titled Define Vector. When you click the
Define Vector command button, GAMBIT opens the Vector
Definition form, which allows you to specify parameters that
define the path vector.
Type:
--------------------------------------
Rigid
specifies a rigid sweep operation.
Perpendicular
specifies a perpendicular sweep operation.
Option:
---------------------------------
Draft
specifies the perpendicular draft method.
Twist
specifies the perpendicular twist method.
Angle
specifies the draft or twist angle.
Type:
-------------------------------
Extended
specifies that an expanded profile projection reflects the basic
shape of the profile.
Round
specifies that an expanded profile projection is to contain
rounded edges.
Mixed
employs elements of the Extended and Round options to fill
gaps in the expanded profile.
Label
specifies a label for the new volume.
Revolve Real Faces
The Revolve Real Faces command allows you to form a volume by revolving a face
through a specified angle
To create a volume by means of the Revolve Real Faces option, you must specify the
following parameters:




One or more faces to be revolved
The axis of rotation
The angle through which the face is revolved about the axis
Draft angle and type
The rotational axis does not have to be coincident with one of the edges of the face to be
swept, but it must lie in the same plane as the profile face (see Figure.)
: Face revolve parameters
Specifying Faces to Be Revolved
To create a volume by means of the Revolve Real Faces form, you must specify one or
more faces to be revolved about the axis of rotation. Each specified face can include any
combination of straight and curved edges as long as all the edges comprising the face lie
in a single plane.
Specifying the Axis of Rotation
In order to constitute a valid axis of rotation for the face-revolve operation, the axis must
lie in the plane of the face. To specify the axis of rotation, you must define the axis by
means of the Vector Definition form. Specifying the Angle of Rotation
The angle of rotation is defined according to the right-hand rule relative to the direction
of the axis vector. That is, when the rotational axis is oriented such that its vector points
away from the observer, angles swept in the clockwise direction are defined as positive
(see Figure, above).
Specifying Draft Angle and Type
When you create a volume by revolving a face, GAMBIT allows you to specify a draft
angle and type to be applied in conjunction with the revolution of the face. The draft
angle represents the extent to which the profile is expanded or contracted as the face is
revolved. The draft type determines whether or not the edges of an expanded profile are
rounded in the process of creating the volume.
Figure shows two volumes created by revolving a rectangular face and specifying a
positive draft angle—that is, an expansion of the profile. In Figure (a), the draft type is
extended, therefore the basic shape of the face does not change as it is revolved. In Figure
(b), the draft type is round, therefore the corners of the revolved face are rounded with
respect to the original profile.
Revolving faces—effect of draft angle and type
Using the Revolve Real Faces Form
To open the Revolve Real Faces form (see below), click the Revolve Real Faces
command button on the Geometry/Volume subpad.
The Revolve Real Faces form includes the following specifications.
Faces
specifies one or more faces to be revolved.
Angle
specifies the angle through which the face is to be revolved.
Deg
Rad
specifies the units for the angle of revolution as either degrees
(Deg) or radians (Rad).
Axis:
contains two components:


A Define command button that allows you to define the
axis around which the edge is to be revolved
The coordinates of the start and end points for a vector
defining the rotational axis
Draft:
--------------------------------------
Extended
specifies expanding or contracting the profile face as it is
revolved according to the specified draft angle.
Round
specifies that the corners of an expanded profile are rounded.
Angle
specifies the draft angle.
Label
specifies a label for the new volume.
Form Real Volume From Wireframe
The Form Real Volume From Wireframe command allows you to form a volume from
a set of existing edges.
To create a volume by means of the Form Real Volume From Wireframe option, you
must specify a set of edges that define the volume. The edge specifications are subject to
the following restrictions:



The set of edges must describe an entire closed volume
All specified edges must possess at least one endpoint vertex that is coincident
with that of one other edge in the set
All edge loops must be joined to the overall set of loops
GAMBIT does not require that edges specified for the wireframe are connected at their
endpoints. During the creation process, GAMBIT deletes coincident vertices, thereby
connecting the edges used to form the volume.
Figure shows four different sets of edges, only one of which constitutes a valid wireframe
for the creation of a volume by means of the Form Real Volume From Wireframe
form. Each set represents a slight variation on a set of edges that constitutes the
wireframe of a cube. The sets shown in Figure are allowed or not allowed for the
following reasons:
1. Allowed—All of the edges possess at least one endpoint vertex that is coincident
with that of at least one other edge; there are no edges that are wholly internal to
the cube
2. Not allowed—The circular edges of the cylindrical region cannot be joined to any
part of the edges that comprise the cube
3. Not allowed—There are four edges in the set that cannot be joined in to the edges
of the cube
4. Not allowed—The edges of the pyramidal region exist entirely within the volume
represented by the edges of the cube
Allowable wireframe configurations
If GAMBIT cannot resolve the specified set of edges into a valid volume, it completes as
much as the creation process as is possible-including the creation of faces-and displays a
warning in the Transcript window.
Using the Form Real Volume From Wireframe Form
To open the Form Real Volume From Wireframe form (see below), click the Form
Real Volume From Wireframe command button on the Geometry/ Volume subpad.
The Form Real Volume From Wireframe form includes the following specifications.
Edges
specifies the edges to be used in forming the volume.
Label
specifies a label for the new volume.
Create Volume
The Create Volume command button allows you to perform the following operations.
Symbol
Operation
Description
Create Real Brick
Creates a volume in the shape of a
rectangular brick
Create Real
Cylinder
Creates a volume in the shape of a
cylinder
Create Real Prism
Creates a volume in the shape of a regular
prism
Create Real
Pyramid
Creates a volume in the shape of a
truncated pyramid
Create Real
Frustum
Creates a volume in the shape of a frustum
Create Real Sphere
Creates a volume in the shape of a sphere
Create Real Torus
Creates a volume in the shape of a torus
Boolean Operations
The Boolean Operations command button allows you to perform the following
operations.
Symbol
Operation
Description
Unite Real Volumes
Unites two or more real volumes into one
real volume
Subtract Real
Volumes
Subtracts the intersecting region(s)
between two or more volumes
Intersect Real
Volumes
Creates a volume representing the
intersection between two or more volumes
In the next class the concepts of meshing and the zone type specifications will be
discussed which almost completes the gambit part. Then fluent part will be discussed.