Unigraphics NX8 - Surface

[NX8-HELP] SURFACE 1

Surface drive24ward (meslab.org/mes)

Surface View a topic

Four Point Surface

Sheets From Curves

Bounded Plane

Transition

Through Points and From Poles

From Point Cloud

Ribbon Builder

Midsurface

Patch Openings

1. Four Point Surface

Use the Four Point Surface command to create a surface by specifying four points.

This is useful for creating base surfaces that support the surface based Class-A workflow. You can easily

modify such a surface by increasing the degree and patch into a more complex surface with the desired

shape.

You must follow these point specifying conditions:

No three selected points can be collinear.

No two selected points can be the same or at the very same location in space.

Four points must be specified to create the surface. If you specify three or fewer points an error

message is displayed.

Four Point Surface

Where do I find it?

Application Modeling

Menu Insert→Surface→Four Point Surface



1.1. Create a surface using four points

1. Choose Insert→Surface→Four Point Surface to open the Surface by 4 Points dialog box.

2. Select the four surface corner points in the graphics window. You can specify the four points

using any of the following methods:

o Select an existing point in the graphics window.

o Select any arbitrary point in the graphics window.

o Define the coordinate location of a point using the Point Constructor dialog box.

o Select a base point and create a point offset from the base point.

Note The Snap Point options are useful when you want to specify an existing point on a

particular curve or surface.

4. Four specified points

5. Specifying subsequent points displays a polygonal preview on the screen. You can modify any

points before finalizing the shape of the surface.

6. Change the location of the points as required.

7. Relocated specified points

8. Click OK or Apply to create the surface.

9. Four Point Surface feature



1.2. Four Point Surface options

Specify Points

Specify Point 1 - 4

Lets you select the first, second, third, and fourth points for the four point surface.

Preview

Preview Select this check box to see a preview of the resulting surface.

2. Sheets From Curves

This option lets you create bodies through selected curves.

Note Many illustrations in this section use solid fill shading to represent wire frame parts. The fill often

hides portions of curves that would be visible in a wireframe model. The purpose is to represent the

concepts with clearly recognizable figures at the loss of some technical viewing accuracy.

Local Settings

When you choose Sheets From Curves, the following options appear:

Cycle By

Layer

Processes all selectable curves one layer at a time. To speed up the processing, you may wish

to turn this option ON. This causes the system to create bodies by processing all selectable

curves one layer at a time. All the curves defining a body must be on a single layer.

Note Using the Cycle By Layer option can significantly increase processing performance.

This option also significantly reduces the use of virtual memory. If you receive the

message: Virtual Memory Exhausted, you may want to spread the wireframe geometry

over several layers. But be sure to place all defining curves for a body on a single layer.



Warnings Causes the system to stop processing and to display warning messages after generating

bodies, if there are any warnings. You are warned about nonclosed planar loops of curves,

and non planar boundaries. If you select OFF, you are not warned, and processing does not

stop.

Basic Procedure

To convert curves to sheets, you must:

1. Set the Cycle By Layer toggle switch as desired.

2. Set the Warnings toggle switch as desired.

3. Choose OK.

4. Choose the curves you wish to sheet using the Class Selection Tool.

5. Choose OK.

The message Creating Bodies appears during this stage of processing. The system then uses all selected

curves to generate bounded planes, cylinders, extruded bodies, and truncated cones.

Tips and Techniques

You can generate bodies using any planar curve. Sheets From Curves creates the following bodies:

Bounded planes - by forming planar closed loops (using the ends of curves)

Note Single planar loops must be periodic.

Cylinders - by pairing circles and ellipses with coaxial centers.

Cones - by pairing arcs with coaxial centers.

Extruded bodies - by pairing conics and planar splines. They must be on parallel planes and one

must project onto the other (via a translation perpendicular to the planes of the curves).

You can create bodies on one plane using:

Loops of objects - These form a bounded plane. For example, the adjoining lines on any face of a

simple rectangle.

You can create bodies between two parallel planes using:

Coaxial arcs - For example, two circles with the same radius become a cylinder, and two circles

having different radii become a cone. In both cases, they share the same axis and are parallel.

Identical splines, parabolas, ellipses, hyperbolas - These form an extruded body; for example, the

thickness of the sole of a shoe.

Note Two coaxial conics do not always have to lie on parallel planes. An ellipse and arc on

nonparallel planes can match and form a body if they are both segments of the same

cylinder. These objects appear similar when viewed along their common axis. See the figure

below.



Sheets From Curves does not create spherical sections. Before using this option, you must create sheets at

all sections of spheres. This option also does not create typical ruled sheets.

2.1. Sheets From Curves Design Considerations

Sheets From Curves usually develops the sheets you desire. However, you will be successful if you

follow certain design requirements:

Guiding Lines

Use guiding lines in ambiguous situations - You must connect defining arcs/ellipses if there are more than

two, and they are coaxial and geometrically similar (that is, the same size in degrees but not necessarily in

arc length). Otherwise the processor cannot determine which object to connect. See the figure below.

You must use arcs (not ellipses) to generate cones. The system always generates truncated (nonpointed)

cones.

It is always safest to create guiding lines using arc endpoints. But you can connect any points on two

circles if the guiding lines do not touch. If they do touch, you must use arc endpoints. See the figure

below.



"Soft Edge" Recognition - It is not necessary to create guiding lines to form a bounded plane if there are

only two identical coaxial arcs limiting the plane. See the figure below.

Guiding Line Rules

When in doubt - use a guiding line.

In the figure below, area A shows that two coaxial arcs of the same size do not require guiding lines. The

processor is able to match the partial arcs and the full arcs without additional help.

However, in area B you must indicate whether the circles should form cones or cylinders.

Area C requires you to match the 4 lower arcs with 4 upper arcs. Because there are more than 2 similar

coaxial arcs you must connect the arc endpoints of the matched arcs. That requires eight guiding lines.



Bounded Plane Rules

Bounded plane object members must form a single unambiguous closed loop. A closed loop does not split

and has no "dangling" object. Therefore the loop is reliably chainable.

In the example shown in the figure below, the boundary members of both front faces do not chain because

the upper line segment extends outside of each boundary.



Normally the solution is to create two segments. However, in this particular example, the following

requirement further prevents sheet generation.

Only two coplanar objects can share an endpoint. This option cannot reliably create a body if a boundary

member object shares a common endpoint with more than one other object on that plane.

In the figure below, even though you subdivide the dangling line, you still may not succeed in creating

bodies the front faces. This is because each face has more than 2 coplanar objects that meet at a vertex.

Notice that lines 1, 2, and 3, in the figure below, are all on the same plane. They also share a common

endpoint. No. 1 effectively becomes a dangling line and that face is not turned into a sheet.

Lines 1, 2, and 4 present the same problem in another plane.

You must manually create sheets for these faces.

Bounded planes must not contain more than two colinear line segments. You cannot create a sheet if three

or more sequential lines are colinear. In the figure below, the front slope is moved towards the center of

its front face. The processor cannot create a bounded plane for the top sheet using the three colinear lines.



You can generate a trimmed bounded plane if the interior objects do not touch or cross the boundary.

Assemblies

Place multiple assembly components on separate layers. They often have curves that cross or touch. The

figure below shows the bottom component trimmed by the base of the top component. The base of the top

component is not turned into a sheet either.

Multiple components on a single layer can cause more than 2 curves on the same plane to share a

common endpoint. Therefore, the bodies might not be properly created, or created at all. See the figure

below.



Invalid Sheets

Trimmed Cylinders - You cannot generate a trimmed cylinder. The interior curves are either ignored or

converted as usual.

Not all sheets are generated, such as unknown sheet types and sections of spheres. See the figure below.



2.2. Error Messages and Warnings

The following is a list of errors and warning messages you might receive. The warning messages are only

received when the Warnings option is turned ON:

When all virtual memory is used, the following error message is displayed. If this message occurs, put

wireframe components on different layers and use Cycle By Layer.

Virtual Memory Exhausted

When the loop of curves is not closed, this warning is displayed. This usually occurs at the endpoints of

two neighboring boundary curves. Occasionally this warning is displayed for legitimate planar strings

which are not intended to form bounded planes.

Planar Loop Is Not Closed

All of the curves which could not be attached to any loop on the plane, and not identified by the warning

Planar Loop Is Not Closed, are displayed with the following warning message. This usually means that

the curves are parts of loops which are disconnected. Occasionally this warning is displayed for open

loops which form legitimate planar strings which are not intended to form bounded planes.

Planar Loop(s) Are Not Closed

The following warning message means there are gap(s) in the chain of curves.

Boundary Not Chainable

The following warning message means the curves of a bounded plane are not coplanar.

Boundary Not Planar

The following warning message means the curves of a peripheral loop or hole, loop in a bounded plane

intersect.

Boundary Intersects

The following error messages mean that a sheet body could not be created from the specified surface.

Unable to Create Sheet Body Unable to Create Planar Sheet Body

3. Bounded Plane

Use the Bounded Plane command to create a planar sheet body enclosed by a set of end-connected planar

curves. The curves must be coplanar and form a closed shape.

To create a bounded plane, you must establish its boundary, and if necessary, define any internal

boundaries (holes). You can define the boundaries by selecting individual curves, or you can use

Selection Intent, as shown in the following animation.



Two different bounded planes created on the same surface, one with holes and one without

Selection Intent's Tangent Curves rule used to create a bounded plane without holes.

Selection Intent's Region Boundaries rule used to create a bounded plane with holes

Where do I find it?


Toolbar Surface→Surface Drop-down→Bounded Plane

Menu Insert→Surface→Bounded Plane

3.1. Create a bounded plane

1. Choose Insert→Surface→Bounded Plane.

The Bounded Plane dialog box opens, and in the Planar Section group, Select Curve is

active.

2. Specify the planar section by selecting an unbroken string of bounding curves or edges. They must

be coplanar and form a closed shape.

3. Preview of bounded plane after selecting a single string of face edges

4. (Optional) You can do the following:



o If there are discontinuous holes within the area bounded by the selected curves or edges

that you do not want included in the bounded plane, select them as inner boundaries.

o Two holes specified by selecting them as inner boundaries

o Use Selection Intent rules to quickly select the closed shapes that define the bounded plane

you want.

5. Click OK or Apply to create the bounded plane.

3.2. Bounded Plane options Planar Section

Select

Curve

Lets you select a closed string of end-to-end curves or solid edges to form the boundaries of

the bounded plane.

The bounding string can consist of single or multiple objects. Each object can be a curve, a

solid edge, or a solid face.

A hole in a bounded plane is defined as an internal boundary where the sheet is not created.

You can create the bounded plane with or without holes, either by individual selection or by

using Selection Intent rules.

4. Transition

Use the Transition command to create a Transition feature at the intersection of two or more sectional

curves.



You can:

Impose either a tangent or a curvature condition on the sections.

Have a different number of elements for the sections.

If you do not use a surface to impose match conditions on a section, a tangent condition is imposed that is

normal to the plane of the input section.

The Transition feature is parametric and associative to any geometry used in its creation.

Three sections (numbered) form a Transition feature

Where do I find it?


Toolbar Surface→Transition

Menu Insert→Surface→Transition

4.1. Create a Transition feature

1. Choose Insert→Surface→Transition.

2. Select the section elements for the first section. To aid selection, you can set the filter on the

Selection bar to Curve, Edge or Sketch.

3. In the Continuity group, set the continuity to (G0) Position, (G1) Tangent, or (G2) Curvature

and click OK.

The section is added to the list in the sections window.

4. (Optional) Click Reverse Direction if you need to reverse the section direction.

5. Repeat this sequence for each section you want to add to define the Transition feature.



6. Preview of Transition feature using two sections

7. As you add sections, a wireframe preview of the point mapping between each of the sections is

automatically displayed.

8. Preview of Transition feature using three sections

9. After you have added all the sections, you can :

o Dynamically edit, insert and delete any of the bridge curve coupling points using the

options in the Support Curves group.

o Dynamically edit the shape of the bridge curves using the options in the Shape Control

group.

o Preview the Transition feature before you create it.

10. In the Settings group, select the Create Surface check box to create the Transition feature as a

surface. If you do not select this check box, only bridge curves are created.

11. Click OK or Apply to create the Transition feature.



12. Transition feature

4.2. Transition options Sections

Select Curve

Lets you select the elements for each section. The section elements can consist of

splines, lines, arcs, conics, surface edges, sketches and so on.

Reverse

Direction

Lets you reverse the section direction so that bridge curves can be remapped.

Specify Origin

Curve

Lets you specify the origin curve in each set of section curves.

Add New Set

Lets you add a new set of section curves.

List

List window

Shows a list of all the sections that you specified, their continuity, and their flow

direction.

Select (or deselect) a surface to change the flow direction at the selected section.

Changing the continuity of one section changes the continuity of all sections.

Constrain Faces



Select Face

Lets you select faces to specify the constrain surfaces.

Support Curves

Show All Points

on Section

Displays all the section points of the selection section set. You can then select one of

the section's points.

List window Displays the coupling points of the selected section curve.

Add

Adds coupling points to the selected section curve.

This option lets you add new coupling points and bridge curves to a section.

You can click Add to insert a coupling point in the section in front of the

currently selected point. The coupling point is added to the coupling point list, and a

bridge curve is added between the selected section and another appropriate section

that is determined by the software.

Remove

Removes the selected coupling point from the section curve.

This option lets you delete a coupling point from a section and its associated bridge

curve from a section. The option becomes available when the selected coupling point

has a coupling point associated with the other end of the bridge curve.

When you delete a coupling point, it is removed from the coupling points list, and its

related bridging curve is also removed.

Move coupling

point to other

section

Lets you move the coupling point to another section curve.

This option becomes available if it is possible to move the selected coupling point to

another section.

When you click the icon, the coupling point is removed from the list and moved to

the appropriate section.

Location

Lets you specify the location of the coupling point.

The slider becomes active when the point is a coupling point. It shows the correct

positional value of that point on the section (0.0 to 1.00 relative to the section length).

You can drag the slider to move the coupling point on the section.

Shape Control

Bridge Curve

Displays a list of all the individual curves and bridge curves you want to edit. You

can select bridge curves individually or as a group.

When you select a section that has the bridge curves you want to edit, this list updates

automatically.

Type

Lets you specify the type of shape control method from the following options:

Depth and Skew — Lets you change the depth and skew of the selected curve

or group of bridge curves in a fashion similar to that used by the Bridge

Curve command.



When you select a curve or group of bridge curves from the Bridge Curve

list, the curve is highlighted in the graphics window. You can then either drag

the Depth and Skew sliders to shape them or enter the required values in the

data fields.

Tangent Magnitude — Lets you change the tangent magnitude of the

selected curve or group of bridge curves.

When you select a curve or a group of bridge curves from the Bridge Curve

list, the curve is highlighted in the graphics window. You can then drag the

Start and End sliders to shape them, or enter the required values in the data

fields.

Depth

Available only when Type is set toDepth and Skew.

Changes the depth of the selected bridge curve. You can either drag the Depth slider

or enter the required values in the data field.

For an example, see Changing the depth value of the selected bridge curve.

Skew

Available only when Type is set toDepth and Skew.

Changes the skew angle of the selected curve or bridge curve . You can either drag

the Skew slider or enter values the required values in the data fields.

For an example, see Changing the skew angle of the selected bridge curve.

Start

Available only when Type is set to Tangent Magnitude.

You can drag the Start slider to shape the start of the curve or enter the required

values in the data field.

For an example, see Changing the start value of the selected curve.

End

Available only when Type is set to Tangent Magnitude.

You can drag the End slider to shape the end of the curve or enter the required values

in the data field.

For an example, see Changing the end value of the selected curve.

Continuity

Continuity

Lets you assign the type of mating condition for the sections. Select from the

following options:

G0 (Position)

G1 (Tangent)

G2 (Curvature)

Note A surface must be selected to use G2 (Curvature).

You cannot assign G1 (Position) or G2 (Tangent) continuity to the faces

comprising the bottom of a Transition feature.

Settings



Create Surface

Create the Transition feature as a surface.

Note Only bridge curves are created if this check box is not selected.

5. Through Points and From Poles

The Through Points and From Poles free form features options use the same interactive creation

techniques, so they are described together in this section.

Through Points - Lets you define a rectangular array of points through which the body will pass. The

body interpolates each specified point. Using this option, you have very good control over the body

in the sense that it always passes through the points that you specify.

From Poles - Lets you specify points as poles (vertices) of a control net which defines the shape of

the sheet. Using poles gives you much better control of the overall shape and character of the body.

Using this option also gives you a much better chance of avoiding unwanted undulations (reversals

of curvature) in the sheet.

The options on the Through Points and From Poles dialogs are the same.

Through Points and From Poles Dialog Options

Patch Type Lets you create a body containing a single patch or multiple patches.

Closed

Along

Lets you select a method for closing a multiple patch sheet body.

Row

Degree

Lets you specify the row degree (1 to 24) for a multiple patch. For a single patch, the system

determines the row degree from the row with the highest number of points.

Column

Degree

Lets you specify the column degree for a multiple patch (up to one less than the number of

specified rows). For a single patch, the system sets this to one less than the number of

specified rows.

Points

From File

Lets you define the points by choosing a file that contains them.

5.1. Create a Through Points & From Poles surface

To create a body using Through Points or From Poles, you must:



1. Choose a Patch Type.

2. For multiple patch, choose a Closed Along method for closing the sheet body.

3. For multiple patch, enter the degrees for rows and columns. You do not have to specify degrees

for single patch.

4. Specify rows of points or poles to be used to create the body, using either the Point Specification

Method dialog or by using specifying a file containing the point definitions.

Patch Type

Single creates a body consisting of only one patch.

Multiple creates a body consisting of a rectangular array of single patches.

Closing the Patch

Closed Along lets you choose a method for closing a multiple patch sheet body using the following

options:

Neither The sheet body begins and ends with the specified points.

Rows The first column of points/poles becomes the last.

Columns The first row of points/poles becomes the last.

Both Closes the body in both directions (rows and columns).

If you choose to close the body in both directions or you close the body in one direction and the other

direction the ends are planar, a solid body is created.



Degrees for Single Patch Bodies

For a single patch body, the system determines both the row and column degrees for you, depending on

the points/poles and rows that you specify.

The Row Degree (U direction) comes from the row with the highest number of points.

The Column Degree (V direction) is equal to one less than the number of rows you specify.

Note The minimum number of rows or points per row is two (minimum degree of one) and the maximum

number of rows or points per row is 25 (maximum degree of 24 + 1).

The sheet shown in the figure below has 4 rows of points, so its column degree (V degree) is equal to 3

(=4-1). The largest number of points in any row is 6, so the rows degree (U degree) is equal to 5 (=6-1).

Degrees for Multiple Patch Bodies

For a multiple patch body, you must specify degrees for the rows and columns.

The Row Degree can be any number from 1 to 24. The default is 3.

The Column Degree can be set to any number from one to one less than the number of rows you specified.

The default is 3.



Note The minimum number of rows or points per row is two (minimum degree of one) and the

maximum number of rows or points per row is 25 (maximum degree of 24).

For example in the figure below, the row degree can be set to any number from 1 to 4. The column degree

is equal to 3.

Points/Poles

Once you have specified the degree and set the Patch Type and Closed Along parameter values, you must

specify the points in one of the following ways:

Choose OK, then specify the rows of points using the Ordered Point Constructor, or the rows of

poles using the Point Constructor.

Choose Points From File and specify the name of the file containing the point definitions. It must

be a Rows of Points type file.

If you use the first method, when you have specified two or more rows of points (enough to satisfy the

degree), you are prompted with two options:

All Points Specified Creates the body and returns you to the dialog.

Specify Another Row Lets you specify another row of points for the body you are creating.

5.2. Tips and Techniques

When specifying creation points or poles, you should select them by row in approximately the same order.

Otherwise, you might get undesirable results. The figures below show different object selection orders

and the resulting bodies.



6. From Point Cloud

From Point Cloud lets you create a sheet body that approximates a large "cloud" of data points,

typically produced by scanning or digitizing. While there are some restrictions, this function lets you

create a body from a large number of points with a minimum amount of interaction.

The resulting sheet body is much "smoother" than one created from the same points using the Through

Points method, but is not as close to the original points.

From Point Cloud Feature Dialog Options

Select Points Lets you select points when this icon is active.

Points From

File

Lets you define the points by choosing a file that contains them.

U Degree V

Degree

Let you control the degree of the sheet body in both U and V directions. The default

degree of 3 can be changed to any value from 1 to 24. (The default of 3 is recommended.)

#U Patches

#V Patches

Let you specify the number of patches in each direction. The combination of degree and

patches in each direction controls the distance error between the input points and the

generated sheet body.

Coordinate

System

Consists of a vector approximately normal to the sheet body (corresponding to the Z axis

of the coordinate system), and two vectors that indicate the U and V directions of the sheet

body (corresponding to the X and Y axes of the coordinate system).



Boundary Lets you define the boundary of the sheet body that you are creating.

Reset Lets you create another sheet body without leaving the dialog.

Confirm

Upon Apply

Opens the Confirm Upon Apply dialog after you choose Apply, letting you preview the

results, and accept, reject or analyze them. This option is common to Selection Steps

dialogs.

In general, there are few requirements for the points you can use to create a sheet body with this function.

There is no restriction on the number of points, other than available virtual memory. The degree and

number of patches in the resulting sheet body is controlled by you, and is not determined by the number

of specified points.

There is no requirement on the organization of the points that are input. They may or may not be

organized in "scan lines".

Part of the information you must supply is a temporary coordinate system. The intended sheet body must

not "fold under itself" when viewed along the Z axis of this coordinate system; that is, for any given point

in this view there must be only one, unambiguous place it can exist on the sheet body.

Basic From Point Cloud Procedure

Following is the general procedure to create a From Point Cloud body. Also, see the abbreviated "quick"

method procedure.

1. Select the points, or specify a file that defines the points.

2. Specify the U and V degree of the surface.

3. Specify the number of patches in the U and V directions.

4. Specify the local U-V coordinate system.

5. Specify the boundary around the desired points.

6. Choose OK or Apply to create the sheet body.

The "Quick" Method

If you do not intend to specify a particular coordinate system, and you do not need to specify a boundary

around the desired points, you can use this "quick" method:

1. Orient your view so that you are looking down on the shape of the desired sheet body.

2. Drag a selection rectangle to enclose the desired points.

3. Enter the desired values for the degrees and patches.

4. Choose OK or Apply to create the sheet body.

6.1. From Point Cloud Options Select Points

This is a required step, and the first step in creating a From Point Cloud sheet body. Notice that, when the

dialog first appears, the Select Points icon is active.

There are two ways you can specify the points:



Select the points by clicking and dragging a rectangle or by selecting them individually.

Robust selection is available, so you can add or remove points from those selected. As soon as you

select points, a boundary is displayed that encloses all the selected points, and the U and V

directions are displayed by vector arrows. As you select and deselect points, the size of the

boundary changes.

Choose Points From File, then specify one or more files containing the point definitions. Each

point file must be a Series of Points type file.

Note If you use more than one point file, only the name of the last point file is stored in the

POINT_FILE object attribute.

#U Patches, #V Patches

These options let you specify the number of patches in each direction. The combination of degree and

patches in each direction controls the distance error between the input points and the generated sheet body.

The number of patches you should specify depends on the degree of the sheet body in the corresponding

direction, the shape of the data in that direction, and the tolerance you are trying to achieve. A general

rule of thumb is that you need one patch each time the slope varies as much as 90 degrees in the

corresponding direction. You can use fewer segments with higher degrees.

Coordinate System

The coordinate system that you choose consists of a vector approximately normal to the sheet body

(corresponding to the Z axis of the coordinate system), and two vectors that indicate the U and V

directions of the sheet body (corresponding to the X and Y axes of the coordinate system).

You have five options for defining the coordinate system:

View of

Selection

The U-V plane is in the plane of the view, and the normal vector is normal to the view.

The U vector points to the right, and the V vector points up.

WCS The current Work Coordinate System.

Current View The coordinate system of the current work view.

Specified

CSYS

Selects the coordinate system previously defined by using Specify New CSYS. If a CSYS

has not been defined, this will behave just like Specify New CSYS.

Specify New

CSYS

Brings up the CSYS Subfunction, which you can use to specify any coordinate system.

With the View of Selection method, if you rotate the view (or modify it in some other way) after selecting

points, this coordinate system may be different from the Current View coordinate system. (Or, if you

select from a view other than the work view in a multiview layout, the View of Selection coordinate

system is different from the Current View coordinate system.)

It is important to remember that the normal vector of this coordinate system does not need to be exact. It

simply must satisfy the requirement that, when the points are viewed down this vector, they not form a

sheet body that folds under itself. Many vectors can meet this requirement (see the figure below).



If a normal vector is specified that violates this requirement, the resulting sheet body will be dramatically

different and probably not what you want.

As soon as you specify a coordinate system, the boundary is redisplayed, as projected onto the new U-V

plane.

6.2. Boundary

The default boundary for the sheet body is generated by projecting all selected data points onto the U-V

plane (see the Coordinate System section). The minimum rectangle that encloses those points is found

and projected along the normal vector onto the cloud of points. This is the option called Minimum Box.

Sometimes this default boundary is not appropriate for your data, and you need to define the boundary

yourself. For example, arrows in the figure below indicate areas inside the boundaries that have no points.

Unconstrained areas such as this within the boundaries can result in wild twists in the sheet body, as

shown in the figure below. Areas that were unconstrained, because they did not contain any points, are

erratic in the sheet body produced.



In a case such as this, you may wish to specify a different quadrilateral (four sided polygon) to be

projected onto the point cloud. You do this by specifying four corner points, which are projected onto the

U-V plane along the normal axis. The resulting quadrilateral must be convex. The figure below shows an

acceptable quadrilateral shape and two unacceptable shapes.

Initially the Minimum Box option is specified. To specify a boundary other than the default, choose

Specify New Boundary from the Boundary option menu. The Point Constructor dialog is displayed and

the Cue line prompts you to specify the first corner. As points 2 through 4 are specified, they are

connected by straight lines, finally forming a quadrilateral.

After you successfully specify the new boundary, the Specified Boundary option is displayed on the

button. If you choose the Minimum Box or Specified Boundary option, the chosen boundary is displayed

in the graphics window.

Note that specifying a new boundary does not change the U-V plane of the coordinate system. However,

the U and V vectors do change direction within the plane, as shown in the figure below. The direction of

the U vector is determined by connecting the midpoint of the 1-4 segment to the midpoint of 2-3. The

direction of the V vector is determined by connecting the midpoint of the 1-4 segment to the midpoint of

2-3. The direction of the V vector is determined by connecting the midpoint of 1-2 to the midpoint of 3-4

(the V vector is not necessarily perpendicular to the U Vector). the origin is the intersection of these two

lines.



If you specify a new boundary, or toggle the Boundary option menu between Minimum Box and

Specified Boundary, the temporary display of the coordinate system and boundary is updated.

6.3. Creating the Sheet Body

When all your options are correctly set, choose OK to complete point selection, then choose Apply or OK

to create the sheet body. (If you choose Apply, and the sheet body is not what you want, the From Point

Cloud dialog is still displayed. You can then change options and generate the sheet body again.)

After the sheet body is created, the Fit Information dialog is displayed, showing the Average and

Maximum deviation of the sheet body from the data points. Also, the data point that is the maximum

distance from its intended position on the sheet body is highlighted.

In most cases, the system is able to produce a sheet body (if not, an error message is displayed). The sheet

that is created may be close to the points or, in some cases, the result may be dramatically erratic.

Inspecting visually and with the available analysis tools is the only sure method of determining if the

sheet body meets your needs.

The Average deviation and Maximum deviation are an analysis of the distance the sheet body differs

from the original points in the direction of the normal to the U-V plane. The true 3D distance from the

sheet body to the points is never greater than this number and it is usually less. These numbers are most

useful for comparing the results from two different sets of input parameters. You can use Analysis→

Distance to find the true 3D distance for the maximum error point.

To try again with different parameters, choose Undo to delete the sheet body just created. You can then

change any of the parameters and choose Apply again.

Error Messages

Memory limits exceeded. Reduce the number of points, the degree or number of patches.

The above message is displayed when the operation has required more memory than is currently available.

This usually results from too many points, too large a degree, too many patches, or some combination of

the above. Select fewer points and/or reduce the value of the input parameters.

You will need at least %n data points to produce a sheet body.

The above error message is displayed when the number of points selected are not at least (Row Degree +

#Row Patches) * (Column Degree + #Column Patches). In this case, you must select more points or

reduce the value of some of the parameter values.



Points too sparse to constrain sheet body. Use more points, reduce the degree or restrict the boundary.

The above error message is displayed when the number of points and/or their distribution on particular

patches, is not large enough. The distribution of the points on the proposed surface is very important -

each patch on the proposed surface has to have a decent number of points lying on it. You can avoid this

problem by using small numbers of patches. Remember, too, that this function is designed to be used on

very dense sets of points, like the ones you get from laser scanners. It may not work well if you do not

have a sufficient number of points.

Degree must be in the range 1 to 24.

The above message is displayed when the U Degree or V Degree fields are out of the specified range.

Specified boundary must be a convex quadrilateral.

The above error message is displayed if the specified four corners are projected onto the U-V plane and

connected and they do not form a convex quadrilateral.

7. Ribbon Builder Use the Ribbon Builder command to build a sheet body between an input profile and an offset profile.

In the following animation, a sheet body is created between the spline and its offset profile.

Where do I find it?


Toolbar Surface→Surface Drop-down→Ribbon Builder

Menu Insert→Surface→Ribbon Builder

7.1. Create a ribbon sheet

1. Choose Insert→Surface→Ribbon Builder.

2. In the Ribbon Builder dialog box, in the Profile group, click Select Curve and select the

curve or edge(s) representing the shape of the ribbon sheet you want to create.



3. Under Offset View, select an object that defines the direction in which to view the offset. You can

use either of the available vector constructor options to define the vector.

4. Under Offset, specify the distance for the offset.

5. (Optional) Click Reverse Direction to reverse the displayed direction of the offset.

6. Specify the angle for the offset.

7. (Optional) Under Settings, specify the Distance Tolerance and Angle Tolerance values.

8. Click OK or Apply to create the Ribbon Sheet feature.

7.2. Ribbon Builder options Profile

Select Curve

Lets you select the profile defining the shape of the ribbon surface.

Offset View

Offset View

Lets you select an object that defines the direction in which to view the offset.

Vector Constructor: Opens the Vector dialog box.

Inferred Vector: This is the default vector type. Click to see the Vector

list. Select the required vector type, then select objects supported by that vector.

You can change the vector and select new objects as needed.

Offset

Distance Specifies the distance for the offset.

Reverse

Direction

Reverses the displayed direction of the offset specified with Offset View.

Angle

Specifies the angle for the offset.

See the Ribbon Builder example that illustrates how different Distance and Angle values

change the output.

Settings

Distance

Tolerance

Specifies the distance tolerance. The default value is taken from Modeling Preferences.

You can change this value.

Angle

Tolerance

Specifies the angle tolerance. The default value is taken from Modeling Preferences. You

can change this value.

7.3. Ribbon Builder example

The following example illustrates the different outputs you get when you specify different Distance and

Angle values for the selected spline (in the center).



8. Midsurface The Midsurface function is used mainly from the Advanced Simulation application, but it is available

here in Modeling as well. Advanced Simulation's model idealization uses a simplified model whose

behavior can be utilized to model the behavior of a more complicated system. This is performed using the

Midsurface feature.

The model idealization process allows you to create a midsurface feature that resides in a single target

solid. There can only be one midsurface feature in a target solid.

For a description of how to use this option, please see the discussion for Midsurface in the Advanced

Simulation Help.

8.1. Patch Openings

Use the Patch Openings command to create sheet bodies to close openings in a set of faces.

You can:

Patch an opening using a single patch type or a sequence of patch types.

Create special surfacing to patch joggles.

Patch one part of a larger opening, such as in a notch.

Smooth the edges of an opening by creating face extensions along the edges.

Suppress the parametric feature that created the hole.

Control the shape and flow of the patching surface by using dividing curves to break up the

opening.

Create the patches as one feature, or as multiple features.



The image shows the command used to patch a collection of sewn sheet bodies.

— Selected edges of openings to patch

— Patch Openings feature

Where do I find it?


Toolbar Surface→Surface Drop-down→Patch Openings

Menu Insert→Surface→Patch Openings

8.2. Patch multiple openings

1. On the Surface toolbar, from the Surface Drop-down list, select Patch Openings or choose

Insert→Surface→Patch Openings.

In the Patch Openings dialog box, in the Face to Patch group, Select Face is active.

2. Select the faces that have openings that you want to patch.

3. In the Opening to Patch group, click Select Edge and in the graphics window, select the edges of

the openings you want to patch.

For this example, edges of multiple openings are selected.



4. In the Settings group, from the Output list, select Multiple Features.

5. Click OK to create a separate patch for each opening.

8.3. Patch Openings dialog box Type

Type list

Specifies the methods for creating the Patch Openings feature.

Quilted

Patch

Approximates the opening and fills it with a series of patches.

N-sided

Area Patch

Creates an N-sided patch surface with an unrestricted number of

curves or edges that form a simple, open, or closed loop.



Mesh Creates a mesh sheet body to fill the gaps.

By

Removing

Edges

Removes the edges surrounding the opening and merges the

surrounding faces.

Extension

Only

Extends the edges of the opening in a direction that is tangential to

the surrounding faces.

Notch Patches a notch or a cutout area of a larger opening.

Joggle Patches an area of a larger opening, where the boundary of the

opening lies on multiple planes.

Mold

Wizard Face

Patch

Creates a feature set using the Edge Patch method from the Mold

Wizard application. This option is only available when you create

patches.



By

Suppression

Identifies features associated to the edges that make up the opening

and suppresses them to fill the hole. This option is only available

during the create mode. No new features are created.

Note Mold Wizard Face Patch and By Suppression are not available when you edit

patches.

Face to Patch

Select Face

Lets you select faces that have openings that you want to patch.

The selected faces are sewn together and openings are determined after the system

internally sews the faces. Faces which cannot be sewn are ignored.

Preselect

Sheet

Bodies check box

Automatically selects all sheet bodies.

Opening to Patch

Select Edge

Lets you select edges that define the openings you want to patch.

You can select or deselect an entire opening by selecting one of the edges of an opening.

You can only select edges that NX identifies as belonging to an opening.

Dividing Curve

Select

Curve

Lets you specify a bridge curve between two points on the selected edge to divide the

opening into two regions.

The region on one side of the curve is patched.

Limits

Lets you limit the area around the opening to create a partial patch sheet body.

When multiple openings are selected for patching, you can specify limits for only one of the openings.

Limit Point

1

Limit Point

2

Sets a start and end point for limiting the patch.

Location options are available for both points.

Actions

Provides options for creating limits.

Select

Curve

Lets you select a curve to define the limit points. NX uses the

start and end points of the selected curve as Limit Point 1 and

Limit Point 2 respectively.

Reverse Reverses the limit points.

Remove

Limit Points

Deselects any selected limit points.



Joggle Options

Available when Type is set to Joggle.

Specify

Point

Point list

Lets you specify points that define the boundary of the limit path for creating the shelf

surface.

Shelf

Length Sets the length of the shelf surface.

Shelf

Radius

Sets a rounding radius for the shelf surface.

The shelf is created by extruding the edges of the shelf length and rounding off the end of

the extrusion by the shelf radius.

Cutout

Length Sets the length of the cutout for the joggle.

Cutout

Radius

Sets a rounding radius for cutout for the joggle.

The system creates a shape similar to the shelf to cut out the base surface in preparation to

create the joggle patch.

Settings

Output list

Specifies the type of patch that is output.

Single Feature Creates a single feature that includes all the openings.

Multiple

Features

Creates a different feature for each patched opening.

Sew Sews all the patches with the sheet body that has the opening to

create one sheet body.

Note This option works only when you patch openings on a

sheet body.

Ignore Gaps

and

Exterior

Openings check box

Ignores gaps and allows you to select all openings.

When you select this check box, you can:

Filter small openings between faces, such as slivers. NX evaluates each opening to

determine if a sheet body can be created to patch it.

Select exterior openings.

Use this option when a cylindrical body has openings at both ends. You can patch

either of the two ends.

Extension

Distance

Available when Type is set to Extension Only.

Specifies the distance to extend the edges of an opening.



Distance

Tolerance

Sets the value for the Distance Tolerance. For more information, see Modeling

Preferences — General.

Mục lục Surface ......................................................................................................................................................................... 1

1. Four Point Surface ............................................................................................................................................ 1

1.1. Create a surface using four points ........................................................................................................... 2

1.2. Four Point Surface options ....................................................................................................................... 3

2. Sheets From Curves .......................................................................................................................................... 3

2.1. Sheets From Curves Design Considerations ............................................................................................. 5

2.2. Error Messages and Warnings ............................................................................................................... 11

3. Bounded Plane ............................................................................................................................................... 11

3.1. Create a bounded plane ......................................................................................................................... 12

3.2. Bounded Plane options .......................................................................................................................... 13

4. Transition ....................................................................................................................................................... 13

4.1. Create a Transition feature .................................................................................................................... 14

4.2. Transition options .................................................................................................................................. 16

5. Through Points and From Poles ..................................................................................................................... 19

5.1. Create a Through Points & From Poles surface ...................................................................................... 19

5.2. Tips and Techniques ............................................................................................................................... 22

6. From Point Cloud ............................................................................................................................................ 23

6.1. From Point Cloud Options ...................................................................................................................... 24

6.2. Boundary ................................................................................................................................................ 26

6.3. Creating the Sheet Body ......................................................................................................................... 28

7. Ribbon Builder ................................................................................................................................................ 29

7.1. Create a ribbon sheet ............................................................................................................................. 29

7.2. Ribbon Builder options ........................................................................................................................... 30

7.3. Ribbon Builder example ......................................................................................................................... 30

8. Midsurface ..................................................................................................................................................... 31

8.1. Patch Openings ...................................................................................................................................... 31

8.2. Patch multiple openings ......................................................................................................................... 32

8.3. Patch Openings dialog box ..................................................................................................................... 33

Documents

Unigraphics NX8 - Surface