Tutorial

**Objective**:

To provide a template for creating a patch definition with background
source information for a generic type airplane configuration.

**Given:**

-   GridTool executable

-   IGES( International Graphics Exchange Standard) File : **Class.igs**

Begin by creating a new work directory with the **Class.igs** file.

GridTool can be executed by typing ***GridTool*** or ***GridTool option
filename***. A list of the command line arguments is as follows:

**[Arguments (option filename)]{.underline} [Action]{.underline}**

**-h help**

**-d3m d3m_filename read a d3m file**

**-f restart_filename read a restart file**

**-gf GRIDGEN_filename read a GRIDGEN formatted file**

**-g GRIDGEN_filename read a GRIDGEN binary file**

**-pf PLOT3D_filename read a PLOT3D formatted file**

**-p PLOT3D_filename read a PLOT3D binary file**

**-IGES IGES_filename read an IGES file**

**-felisa run GridTool in FELISA Mode**

**-CURVES CURVES_filename read in a CURVES file**

**-dat dat_filename read a dat file**

The GridTool interface consists of a main panel with several contact
sensitive buttons to bring up sub-panels. These sub-panels can be
activated by pressing their buttons from the Main panel window. When a
panel is activated, the button color changes from blue to green. By
placing the mouse cursor over any button and clicking with any of the
three mouse buttons, the corresponding sub-panel will be displayed.

I. INPUT/OUTPUT PANEL

-   Locate the *Input/Output* panel on the screen or depress the \[I/O\]
    button on the GridTool *Main* panel to activate it.

Steps to READ a file:

a.  Select a project name and enter it in the \[Project Name\] field.

b.  Type in the filename in the \[File Name\] field or select it from
    the Files Browser by placing the mouse over the filename and
    clicking with any of the mouse buttons.

c.  Select the type of file format, ASCII or Binary, by placing the
    mouse in the \[File Format\] field and clicking with the leftmost
    mouse button, or press the right mouse button and select from the
    drop-down menu.

d.  Select the appropriate file type by placing the mouse in the \[File
    Type\] field and clicking with the leftmost mouse button. To view
    all the menu choices available, place the mouse in the \[File Type\]
    field and click with the rightmost mouse button. Drag down to select
    and highlight the file type.

e.  Press the \[READ\] button to read the file.

f.  Stow the *Input/Output* panel by pressing the red \[STOW\] button on
    the *Input/Output* panel or pressing the \[I/O\] button from the
    GridTool *Main* panel.

The GridTool restart file is the main file that is used in the program.
Once a new project is started in GridTool, a new restart file should be
generated. The restart file contains all the information in the database
that you have created. Frequent updating of the restart file is
recommended. The restart file will contain the latest software
configuration setup and subsequent additions and changes made.

II\. DISPLAY WINDOW PANEL

Geometry that is read in through the Input/Output panel is displayed in
the DISPLAY WINDOW. When the IGES file is first read in, only the
boundary curves of the entities are displayed with the orientation axis
at the origin. The mouse and hot keys, or the Viewing Controls panel can
be used to manipulate the geometry in 3-D space. The Viewing Controls
panel will be discussed in section lll.

Hot Key Operations:

-   The Hot Key \[x\] -- toggles the axis display on/off.

a\. To remove the axis, press the hot key \[x\] on the keyboard.

b.  To restore the axis, repress the hot key \[x\] on the keyboard.

-   Hot Key Manipulations for Rotation:

    The geometry can be rotated about two sets of axis, the world (body)
    coordinate system and the screen coordinate system. Both axis system
    rotations using the numeric keypad are explained as follows.

[World (Body) Axis Rotation]{.underline}: \[num lock\] \[/\] \[\*\]
\[page down\] \[-\]

The \[num lock\], \[/\], \[\*\], and \[-\] hot keys are located on the
top row of the numeric keypad. The world (body) axis system is relative
to the geometry.

\[num lock\] -- rotation about the world x-axis.

\[/\] -- rotation about the world y-axis.

\[\*\] -- rotation about the world z-axis.

The rotation continues as long as the hot keys are pressed down.

Pressing together both:

\[page down\] \[num lock\] - 90 degree rotation about the world x-axis.

\[page down\] \[/\] - 90 degree rotation about the world y-axis.

\[page down\] \[\*\] - 90 degree rotation about the world z-axis.

Pressing together both:

\[-\]\[num lock\] -- reverses the direction of the world x-axis
rotation.

\[-\]\[/\] -- reverses the direction of the world y-axis rotation.

\[-\]\[\*\] -- reverses the direction of the world z-axis rotation.

[Screen Axis Rotation]{.underline}: \[7\] \[8\] \[9\] \[page down\]
\[-\]

The \[7\], \[8\], \[9\] and \[-\] hot keys are located on the numeric
keypad. The screen x-axis is to the right, y-axis is up, and z-axis is
out of the screen (Right Hand Rule).

\[7\] -- rotation about the screen x-axis.

\[8\] -- rotation about the screen y-axis.

\[9\] -- rotation about the screen z-axis.

Pressing together both:

\[page down\] \[7\] - 90 degree rotation about the screen x-axis.

\[page down\] \[8\] - 90 degree rotation about the screen y-axis.

\[page down\] \[9\] - 90 degree rotation about the screen z-axis.

Pressing together both:

\[-\]\[7\] -- reverses the direction of the screen x-axis rotation.

\[-\]\[8\] -- reverses the direction of the screen y-axis rotation.

\[-\]\[9\] -- reverses the direction of the screen z-axis rotation.

-   The Hot Key \[r\] -- resets the default view (cursor needs to be
    inside of Display Window before hot key is pressed). Pressing the
    \[Reset\] button in the Viewing Controls panel may also restore the
    initial view.

Mouse Operations:

The mouse can be used either in a default mode or in a PLOT3D mode. The
mode can be changed by pressing the \[PLOT3D\] button, which is located
in the Viewing Controls panel. The operations of the mouse are explained
below for both the default and PLOT3D modes:

Mode Movement Left Mouse Middle Mouse Right Mouse

Default Right Translate Rt N/A

Default Left Translate Left N/A

Default Up Translate Up Zoom Out N/A

Default Down Translate Down Zoom In N/A

PLOT3D Right Rotate Screen y Rotate Screen z Translate Rt

PLOT3D Left Rotate Screen --y Rotate Screen --z Translate Left

PLOT3D Up Rotate Screen x Zoom Out Translate Up

PLOT3D Down Rotate Screen --x Zoom In Translate Dn

III\. VIEWING CONTROL PANEL

-   Press \[Control\] button on the GridTool Main panel to activate the
    Viewing Controls panel. This panel contains the mechanisms for also
    manipulating the geometry in 3-D space.

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-   Geometry Rotations and Manipulations in 3-D Space

a.  Reset --Resets the geometry in the Display Window.

b.  Ortho -- Orthographic perception.

c.  D. Cue -- Depth perception cue.

d.  Center of Rotation -- The center of rotation is allowed to be moved
    to any arbitrary point in space. When this button is pressed, a
    Center of Rotation panel appears. The center of rotation can be
    moved to any existing point by using the "x, y, and z" sliders or to
    the centers of the [active]{.underline} surface, curve, patch, or
    point by pressing the corresponding button.

e.  MOUSE PLOT3D -- toggles mouse mode between default and PLOT3D. The
    mouse operations (default and PLOT3D) are listed above in section
    ll.

f.  Clip -- Clipping can be conducted in the z-direction of the viewing
    screen by moving the positioner. The clipping tool is set at the
    maximum viewing volume, starting from the --z direction and at the
    other extreme from the +z direction. Moving the bars closer together
    will shorten the viewing volume.

g.  Rotation and Translation Rates -- Sensitivity rates for rotation and
    translation can be adjusted by pressing the up/down arrows along
    side the \[Rot\] and \[T/Z\] buttons. Each time the arrow keys are
    pressed, the sensitivity rate is increased/decreased by a factor of
    three. To reset to the default value, press the \[Rot\] or \[T/Z\]
    button. Note: These sensitivity rates correspond to both Screen and
    World Axis systems.

h.  Screen Viewing Plane -- The screen viewing plane can be changed to
    any of the following: X-Y, Y-X, Y-Z, Z-Y, Z-X, and X-Z.

> The first axis label listed is in the direction pointing to the right
> of the screen, and the second axis label listed points up to the top
> of the screen.

i.  World Axis Rotation -- operation can be performed by moving "x, y,
    and z" sliders. Ninety degree rotations can be made about the "x, y,
    and z" world axis by pressing the \[90\] button under each World
    Rotation "x, y, and z" slider.

j.  Screen Axis Rotation --Screen axis rotations can be performed as
    follows:

> z-axis rotation -- Move ball in Screen Rotation z display to rotate
> geometry about z Screen axis. While placing mouse cursor over ball,
> press any of the three mouse buttons and drag to conduct rotation.
> Ninety degree rotation can be performed by pushing \[90\] button at
> lower left corner of Screen Rotation z display.
>
> y-axis rotation -- Move y slider to rotate about y Screen axis. Ninety
> degree rotation about y-axis can be performed by pushing \[90\] button
> to the right of the y Screen slider.
>
> x-axis rotation -- Move x slider to rotate about x Screen axis. Ninety
> degree rotation about x-axis can be performed by pushing \[90\] button
> above the x Screen slider.

k.  Screen Zoom - Moving the Zoom slider up or down will cause the
    geometry to zoom out and in relative to the Screen axis system.

l.  Screen Translation - Moving the Translation positioner will cause
    the geometry to by translated in the corresponding direction.

IV\. SURFACE ATTRIBUTES

The *Surface Attributes* panel is used to set surface properties, such
as the color, direction, and number of display paths.

-   Press \[SURFACES\] button from the GridTool *Main* panel to activate
    the *Surface* *Attributes* panel.

This panel controls the attributes of the geometric entities that are
read into the program via the *Input/Output* panel. Entities may be
designated as either surfaces or curves.

-   On/Off Browser

a.  Using the mouse, click and drag on the entity descriptors displayed
    in the On/Off browser. It will be helpful to zoom/rotate the
    geometry to get a look at the surface definition. A typical entry in
    this window might appear as:

> \(A\) O 1 ( 21 x 15) (S) Family Name

(A) \- contains a () for non-active entities or displays (A) for the
    active

entity.

O - means the entity is not currently displayed (Display Type is Off).

1 - indicates the entity's sequence in the file.

(21 x 15) - is the entity size in units of 'display paths'

\(S\) - indicates that the entity is a surface (S) and (C) is a curve.

Family Name - is a user-specified group name for related entities
(families).

The highlighted entities will be displayed in the DISPLAY WINDOW.
Initially, entity #1 is highlighted in RED in the On/Off browser on the
*Surfaces* panel to show that it is the "active" entity. The active
surface is always drawn in magenta in the DISPLAY WINDOW.

b.  To make a different surface entity active, the hot key \[s\] may be
    used. Place the mouse over the intended surface and press hot key
    \[s\] from the keyboard.

Hot Key \[s\] - makes a surface active.

Hot Key \[shift\] \[s\] - places the center of rotation to the active
surface.

-   Changing the Display Type

a.  First, choose the SELECTION TYPE by placing the mouse in the
    \[Selection Type\] Field and pressing the right mouse button to view
    the choices. Select the appropriate choice.

b.  Then select the DISPLAY TYPE by placing the mouse in the \[Display
    Type\] Field and pressing the right mouse button to view the
    choices. Select the desired type.

c.  The appropriate changes will take place in the DISPLAY WINDOW.

-   Changing the Family of an entity

Grouping related entities can ease data manipulation in GridTool. For
example, it is advantageous to group entities into 'families' such as
those associated with the nose, wing, tail, and fuselage. This is
accomplished by changing entity family descriptions, which appear in the
On/Off browser.

a.  Setup geometry so that all entities are displayed in Wireframe Mode:

> \[Selection Type\] : Single
>
> \[Display Type\] : Wireframe

b.  Turn-off all but Surface #1 by clicking with the mouse button on
    Surfaces #2-5.

This leaves the nose surface on. Note (IMPORTANT): A surface being
displayed does NOT imply that it is the active surface. In fact, the
active surface may not even be displayed at any given time.

To change an entity's family name:

a.  Highlight the current family name in \[Family\] field (Default:
    Addams) or press \[Esc\] button to clear the input field.

b.  Type a new name in the \[Family\] field.

c\. Press the \[Change Family\] button to activate the change.

-   Change Display Path of an Entity

> Display paths are used for rendering the surfaces. The default display
> paths are based on the knot vectors defining the NURBS surfaces. The
> number of display paths drawn on a surface can be modified to provide
> a coarser or finer detailed rendering of the surface. The current
> display path counts are displayed in parenthesis in the On/Off
> browser.

a\. To Change the Display Path:

-   Display the surface(s) that will be changed.

-   Enter values in the \[Number of Display Path\] Field.

-   Press \[Change DP\] button.

Values of the Display Path:

> Entering positive values in the \[Number of Display Path\] Field, \[M
> N\], changes the display paths to M x N.
>
> Entering negative values in the \[Number of Display Path\] Field, \[-M
> -N\], multiplies the default U display path count by M and the default
> V display path count by N. Therefore \[-1 --1\] gives the default
> display paths. When entering negative values, the total number of
> display paths for a surface may be calculated by:
>
> Number of \'U\' display paths: M(U-1)+1
>
> Number of \'V\' display paths: N(V-1)+1

-   Change Direction of a Surface

To change the directions of a surface:

a\. Press the \[Arrows\] button.

b\. Turn on all appropriate surfaces.

c\. Press \[Switch Dir\] button.

> d\. Press \[Arrows\] again to turn off arrows.
>
> Rotating the surface will show whether the normal to the surface
> points inward or outward as indicated by the arrow.

-   Change the Background Color

a.  Press Background button.

b.  Background color can be changed by using the three sliders for
    colors or by inputting the RGB color number in the input-fields.

-   Changing Surface Color (Background Button toggled off)

a.  Turn on appropriate surface.

b.  Surface color can be changed also by using the three sliders for
    colors or by inputting the RGB color number in the input-fields.

V. POINTS/CURVES PANEL

a.  Locate the \[Pts/Curves\] button on the GridTool *Main* panel. Press
    it to bring down the *Points/Curves* panel. The points and curves
    menu is used to construct the curves that will eventually become the
    edges of patches. This panel can be used to create, modify, and
    delete points and curves. A curve is represented by a link-list of
    points. These points can be placed on a surface (surface points) or
    somewhere in space (XYZ points). For surface points, the parametric
    coordinates, u and v are stored in the data base, in addition to the
    x, y, and z coordinates.

b.  Use the *Surfaces* panel to display the nose surface in the DISPLAY
    WINDOW and make the nose surface active. Shut-off all other
    surfaces.

c.  Go to *Point/Curves* panel. Press \[Next Curve\] button and then
    press \[Next Point\] button. This sequence starts the construction
    of a curve where this newly created point is the active point. This
    new point is placed where the last point was on the active surface,
    and the user can then move this new (active) point to any location.
    Move cursor over any intersection of display paths on the active
    surface and press hot key \[t\] to move the active point to this new
    location.

> Hot Key \[t\] -- move the [active]{.underline} point (red point) to
> any intersection of the display paths on the [active]{.underline}
> surface (magenta surface).
>
> Hot Key \[m\] - moves the [active]{.underline} point (red point) to an
> [existing]{.underline} point on a curve (this curve does not have to
> be on the [active]{.underline} surface).
>
> Note:
>
> Hot Key \[p\] -- makes an [existing]{.underline} point on an existing
> curve active (red point). This hot key [does not]{.underline} move the
> previously active point to this existing point location.

d.  Next, press \[Next Point\], where again the new (active) point is
    placed where the last point was on the active surface. The user can
    then move this new (active) point to any location by moving the
    cursor to another intersection point on the active surface and press
    hot key \[t\]. Now you see a curve defined by two points. The active
    curve is colored in red and the points on the curve are displayed in
    green except for the active (red) point. All green points signify
    that all the points on the curve lie on the same surface.

e.  Press the \[Enrich\] button with the default -1 to place evenly
    distributed points along the curve. Typing a specified amount of
    points in the \[Enrich\] field will place that many points between
    two existing points on that curve.

In addition to using the hot keys \[t\] and \[m\], the active point can
be moved to any location on the active surface by:

1.  Typing in the parametric coordinates in the "U & V" input box;

2.  Moving the "U & V" positioner;

3.  Moving the "U & V" sliders.

To move the active point to space:

1.  Convert point to a "XYZ" point by pressing \[On Surface\] button.

2.  Once the active point is an XYZ point, the "x, y, and z" sliders can
    be used to move the point to anywhere in space.

A summary of the attributes of the curve is displayed in the
Points/Curves menu. It gives the attributes of the active curve, such
as:

-   Total Number of Curves.

-   The number of points of the active curve.

-   The length of the curve.

-   The family of the current curve.

Remaining Features:

To Split a curve:

a.  Activate a curve by moving the cursor over the curve and pressing
    hot key \[c\].

Hot Key \[c\] -makes a curve active.

b.  Press hot key \[p\] on one of the points on the active curve. This
    is the point at which the curve will be split.

Hot Key \[p\] -make a point active.

c.  Hit \[Split Curve\]. One curve turns green while the other remains
    active

> and is thus shaded red.
>
> d\. Press hot key \[c\] on each curve to activate.

To combine two existing curves:

a\. Make one of the curves active.

b\. Press \[Combine #\] button.

c\. Make the other curve active.

d\. Press the \[Combine Curves\] button.

To copy a Curve:

a\. Activate the curve.

b\. Press \[Copy Curve\] button.

To project a Curve:

1.  a\. Display the projection surface.

> b\. Activate the curve.

2.  c\. Press the \[Project Curve\] button.

> To smooth a curve:

a\. Activate the curve.

> b\. Press the \[Smooth Curve\] button.
>
> Notice that all the points turn blue. The points are not on the
> surface anymore. Project points to the appropriate surface by
> projecting the curve.

To delete a curve:

a\. Activate the curve.

b\. Press \[Delete Curve\] button.

To delete a point:

a\. Activate the point on the curve.

b\. Press \[Delete Point\] button.

To insert a point:

a\. Activate the intended curve.

b\. Activate the point to insert the new point ahead of.

c\. Press \[Insert Point\] button.

To project a point:

a\. Display projection surface.

b\. Activate the point.

c\. Press \[Project Point\] button.

To auto-edge a surface:

a.  Activate the surface.

b.  Press \[Auto Edge\] button.

This will automatically generate curves about the surface boundary.

To Collapse 2 or more points:

(This option collapses [endpoints]{.underline} of curves to a desired
point)

a\. Activate the point to which the others will be collapsed.

b\. Place a tolerance in the \[Gap Size\] Input field.

c\. Press \[Collapse Points\] button.

> A message will appear to tell you how many [endpoints]{.underline} lie
> within the tolerance (not including the active point). Press yes or no
> to proceed with the collapse. (Hint: You should know before hand the
> number of endpoints that should collapse. If it gives you a number
> that you are not expecting, answer \'no\' and inspect the curves and
> points.)
>
> Delete Unused:
>
> Any curve that is not part of an existing patch will be deleted by
> pressing this button.

![](media/image1.wmf){width="5.9944444444444445in"
height="5.330555555555556in"}

Figure 1. Nose surface with bounding curves.

![](media/image2.wmf){width="5.9944444444444445in"
height="5.330555555555556in"}

Figure 2. Nose surface with five curves.

VI\. PATCHES PANEL

-   Press \[Patches\] button from the GridTool *Main* panel.

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-   Hint: Put a 0.0 tolerance in the \[Shrink\] field on the *Misc*
    subpanel to have a patch edge coincide with the curve. Otherwise,
    there will be a noticeable gap between the patch edges and the
    underlying curves. The gap is used for display purposes only and
    does not suggest that there is an actual gap between the patch edge
    and the curves.

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-   To define a Patch:

a\. Activate the curve intended as the first edge of the patch.

b\. Press \[Next Patch\] button, then Press \[Accept Edge\].

> GridTool will suggest a curve to define the next patch edge. If this
> is the desired curve, press \[Accept Edge\] button. If not, press
> \[Find Edge\] button until the appropriate curve is activated.
> Continue accepting edges until the patch is closed. The pink
> arrow(which indicates the direction normal to the patch) will change
> from dotted to solid. Make sure that the normal is pointing in the
> right direction. Press \[Reverse Patch\] if the patch is improperly
> oriented.

![](media/image3.wmf){width="5.9944444444444445in"
height="5.330555555555556in"}

Figure 3. Curves making up patches 1 and 2 on the nose surface.

![](media/image4.wmf){width="5.999305555555556in"
height="6.736805555555556in"}

(bounding box: -10 ≤ x ≤ 13

-5 ≤ y ≤ 5

0 ≤ z ≤ 5)

Figure 4. Basic patch definition of the Class model.

![](media/image5.wmf){width="4.916666666666667in" height="4.375in"}

Figure 5. Nose view of the Class model.

![](media/image6.wmf){width="4.944444444444445in"
height="4.388888888888889in"}

Figure 6. Planform view of the Class model.