2. Getting to Know D3D

2.1 First Things to Know About D3D

2.1.1 Input Devices

2.1.1.1 Mouse (Pointing Device)

The Three-Button Mouse (refer to Figure 2) is D3D's primary input device. Each button performs a number of different actions depending on where the mouse pointer is located and on the selected Viewing Mode. Understanding mouse operations may be the most challenging aspect to learning the system. The mouse pointer is the graphical arrow that appears in the D3D workspace. It indicates the mouse's current position. In all the following sections of this User's Guide, it is referred to as simply the "pointer."

Mouse Button 1 is the primary activator button. This is the button you use to open and close menus and to make most menu selections.

Most of the Mouse actions described in Figure 2 are related to features that are covered in detail in upcoming subsections.

2.1.1.2 Keyboard

D3D uses a standard workstation keyboard.

2.1.2 Start Up and Exit

2.1.2.1 Login

If your system has a screen saver, move the mouse slightly to display the login prompt. The login name and password are assigned by your system administrator and may therefore vary from machine to machine.

2.1.2.2 Start Application

To start D3D, execute the Bourne shell d3d_demo/app/app-d3d, located in the D3D directory. Its best to create a launcher icon to that allows the use to click an icon to start the application. Once the Start D3D splash window (see Figure 3) is replaced by the full-screen D3D application and the D3D Volume Browser appears, the system is ready to load data.

2.1.2.3 Exit

Exit shuts down the D3D workspace application. Find Exit under the File option on the Menu Bar (see Subsection 2.1.6, "Menu Bar"). A dialog box appears in the middle of the display screen when you choose this option, asking you to confirm that you really want to exit.

2.1.3 Layout of the D3D Graphics Display

2.1.4 Windows, Tooltips, Menus, and Dialog Boxes in D3D

2.1.5 Other D3D Operational Information

2.1.5.1 Auto Update

In contrast to D2D, products for D3D are not automatically loaded as new versions of currently-loaded products become available to the system. They need to be manually loaded for display. Auto Update is not currently implemented.

2.1.5.2 Time Matching

Again in contrast to D2D, you cannot add overlays from other models or subsequent model runs to a displayed product. Thus, time matching of products is restricted to the selected model.

2.1.5.3 General Status Messages

When data are missing or incomplete, or there are other problems with the workstation, the system sends status messages, which are displayed in the Status Window. There are three priority levels: Routine, Significant, and Urgent. Routine messages appear in the General Status Area of the Status Bar. A list of these messages are appended to the General Status Dialog Box. Both are shown in Figure 5.

This General Status Dialog Box is opened by clicking on "Status" from the Help Pull-Down Menu found on the Menu Bar. Urgent messages appear in a Red Banner Announcement Dialog Box, shown in Figure 6.

This dialog box is closed by clicking anywhere inside it.

2.1.5.4 System Clock

A workstation's system clock usually appears along the bottom of the Main Display. Additionally, there is a Vis5D model clock with hands in the upper right corner of the Main Display. This refers to model time.

2.1.5.5 Clock and Watch Face Indicators

The D3D Pointer changes to a watch face to let you know the system is processing your request. When you see the watch face the system is busy, but it can still respond to your requests. For example, you can select a product and press the Clear Button to preempt the loading process.

2.1.6 The Menu Bar

2.1.6.1 File

Refer to Figure 8 for a display of this menu.

• Bundles

  Bundles are user-generated lists of graphics and/or image products, which let you define, customize, and save a sequence of products. Bundles provide a convenient way to display commonly used products, or products that are needed for a certain weather scenario.
  
  If, for example, you display 285 K Potential Temperature colored by a customized Height Color Table, you can save this grouping of products, known as a bundle, in a file for future use. Bundles contain not only all the products you overlaid onto the display, but also the display parameters, such as color tables, graphics control settings, isosurface values, etc., and particulars such as zoom factor and viewing perspective.
  
  You can have any number of products in a bundle and then label your file to reflect its contents or with your own name.
  
  

• Cascading Menu

  From the File Pull-Down Menu in the Menu Bar, the Bundles Cascading Menu (Figure 9) can be opened.

New...

The New option opens a New (Empty) Bundle Dialog Box, shown in Figure 10, from the Bundles Cascading Menu.

When first opened, this dialog box is empty, unsaved, and untitled. The buttons in the Bundle Dialog Box are used to save a bundle to a file. By convention use ".sav" as the file extension.

Open...

This option opens the Open Bundle Dialog Box from the Bundles Cascading Menu. This dialog box provides a list of files of currently available bundles. To open an existing bundle, highlight it and click the OK Button at the upper right of the dialog box, or you can double click on the bundle name. You can also type the bundle name on the line provided in this dialog box.

Delete...

This option is not yet implemented.



• Print...

  This option sends everything currently visible in the Large Display Pane to the default printer. Refer to Figure 11.

These printing options should be familiar to most computer users. The gray labeled options are not applicable.



• Movie...(Disabled)

  This option sends a time series of everything currently in the Large Display Pane to the disk. The images are converted to an Mpeg movie or a series of GIF images. Refer to Figure 12.

These options include a filename entry box and a pull-down menu allowing you to select between an Mpeg movie or a time-series of GIF images.



• Exit

  Shuts down the D3D workspace application. A dialog box appears in the middle of the display screen when you chose this option, asking you to confirm that you really want to exit.

2.1.6.2 View

The View Pull-Down Menu, shown in Figure 13, contains options that control the display layout, views, and product animation. Most, but not all, options have corresponding icon buttons in the second row of menu options called the Toolbar.

• Clear Fields

  This option clears all products in the Large Display Pane except for the map background and topography. The selected model remains loaded in memory so new products can be loaded easily. You can also use the Clear Button in the Toolbar.
  
  

• Clear Model

  This option clears the Large Display Pane. The map background remains.
  
  

• Step Back

  This menu option reverses the displayed data by one frame. You can also use the "<" Icon Button in the Toolbar.
  
  

• Step Forward

  This menu option advances the displayed data by one frame. You can also use the ">" Icon Button in the Toolbar.
  
  

• First Frame

  This option displays the first frame of available data. You can also use the "|<<" Icon Button in the Toolbar.
  
  

• Last Frame

  This option displays the last frame of available data. You can also use the ">>|" Icon Button in the Toolbar.
  
  

• Looping

  This check button enables/disables animation. You can also use the Loop Icon Button in the Toolbar.
  
  

• Perspective

  This option toggles between perspective and orthogonal viewing projections. Perspective viewing adds depth to the 3D Display, orthogonal does not. You can also use the Perspective Button in the Toolbar.
  
  

• Top

  This option resets the Large Display Pane to the default top view without changing the zoom factor. You can also use the T Directional Button in the Toolbar.
  
  

• Default

  This option resets the Large Display Pane to the default top view and normalizes the zoom factor back to a value of 1.0.
  
  

• North

  This option sets the Large Display Pane to a north position looking south. You can also use the N Directional Button in the Toolbar.
  
  

• South

  This option sets the Large Display Pane to a south position looking north. You can also use the S Directional Button in the Toolbar.
  
  

• East

  This option sets the Large Display Pane to an east position looking west. You can also use the E Directional Button in the Toolbar.
  
  

• West

  This option sets the Large Display Pane to a west position looking east. You can also use the W Directional Button in the Toolbar.
  
  

• Spin

  This activates a script that spins the 3D Box in the Display Pane demonstrating rotation capabilities. Currently the script cannot be interrupted and must run to completion (one revolution).
  
  

• Zoom

  This activates a script that zooms the 3D Box in the display demonstrating scaling capabilities. Currently the script cannot be interrupted and must run to completion.
  
  

• Toolbar

  This check button option enables/disables the Toolbar, the second row of options along the top of the display. If you need more viewing space in the Display Panes, you can hide the Toolbar. All of the controls in the Toolbar are redundantly placed in the View and Options Pull-Down Menus, so that you can perform all Toolbar actions without the Toolbar. Refer to Subsection 2.1.7, "The Toolbar," for further information.

2.1.6.3 Options

The Options Pull-Down Menu is shown in Figure 14.

It contains popup menus that allow you to select the property options listed as follows.



• Loop Properties

  This option allows you to set the looping properties. You can also use the Loop Properties Button in the Toolbar. Refer to Subsection 2.1.7, "The Toolbar," for further information.
  
  

• Display Options

  These menu options allow you to customize various display properties and preferences in the Large Display Pane, such as the visibility of the bounding box and legends, for example, and selecting the wind glyph type.
  
  Box
  
  On by default, this check box toggles the 3D Bounding Box.
  
  Depth Cue
  
  On by default, Depth Cue causes lines to "fade away" as they get more distant from the viewing position, enhancing the illusion of 3D depth in the Large Display Pane. No depth cues are noticeable, however, when the Large Display Pane's background is colored white.
  
  Grid Numbers
  
  Off by default, this check box toggles the display of horizontal and vertical tags between grid numbers and latitude/longitude and elevation values. This applies to cross sections and cursor positions.
  
  Legends
  
  On by default, this check box toggles the display of color bar legends in the Large Display Pane. Color legends are valid for slices, volume visualization, and isosurfaces when colored by a second field.
  
  Reverse B/W
  
  Normally, the Large Display Pane's 3D Box, labels, and clock are drawn in white on a black background. This option reverses that and draws the box, labels, and clock colored black on a white background. This is useful for making paper printouts.
  
  Alpha Transparency
  
  Transparency controls the degree to which you can see through the front of an object, allowing you to see the back of the object and other objects behind it. Alpha blended transparency (on by default) offers a smooth transparent surface (if supported by hardware graphics). Mesh transparency has a dithered appearance and is sometimes referred to as screen door transparency. It is difficult to present multiple levels of transparency in a scene due to inherent limitations on PEX platforms.
  
  Wind Arrows
  
  The wind glyphs are displayed as wind barbs by default. Select this check box to change the glyph representation to wind arrows/vectors.

2.1.6.4 Tools

The Tools Pull-Down Menu is shown in Figure 15.

It contains popup menus used to locate the 3D Cursor and set the vertical scaling.



• Put Home Cursor...

  Horizontal Location
  
  The Put Home Cursor Dialog Box, shown in Figure 16, has a station list containing a selectable list of METAR and RAOB stations. Click on a Station name with the pointer to instantly move the Probe, Sounding, or Trajectory 3D Cursor to a station location.

Vertical Constraint

Frequently the gross resolution of model generated topography causes both the Probe and Trajectory Cursors to appear below ground. A slider allows you to dynamically set the 3D Cursor to a fixed pressure level or fixed height above ground.



• Set Vertical Scale...

  This option allows you to dynamically set the vertical scale of the model. A default value is available in the entry box when the Set Vertical Scale Dialog Box is first opened, as well as when Default is selected. Entering a value larger than the default value causes the vertical scale of the model to increase. Likewise, entering a value smaller than the default value causes the vertical scale of the model to decrease.

2.1.6.5 Volume

Refer to Figure 17 for a display of this menu.

From this menu you can open the Volume Browser (refer to Subsection 2.3, "The Volume Browser"), which provides access to gridded model data. You can also open the Variable Maker (refer to Subsection 5.1, "Variable Maker"), which enables you to create and generate your own fields on demand.

From this menu you can also select Families. These scripts, similar to D2D Families, are preselected groups of data products which can be displayed with a single mouse click over the script name in this menu. Once a model is selected (from the Volume Browser's Source Pull-Down Menu) the available menu items are shown in black. Unavailable items appear in gray.

2.1.6.6 Surface

The Surface Pull-Down Menu, shown in Figure 18, contains a list of surface scripts.

• Families

  You can select these scripts to load surface data. These Script Products, similar to D2D Families, are preselected groups of data products which can be displayed with a single mouse click over the script name in this menu. Wind barbs and arrow are mutually exclusive glyphs.

2.1.6.7 Upper Air

The Upper Air Pull-Down Menu is shown in Figure 19.

• Trajectory Column

  If Trajectory is selected as the Viewing Mode, you can then select the Trajectory Column from this menu to produce a column of trajectory ribbons at the location of the 3D Cursor. This applies to trajectory "set1" only.

2.1.6.8 Maps

Refer to Figure 20 for a display of this menu and Figure 21 for a display of the slider for movable map option.

The Map Pull-Down Menu has two background map options in addition to a color editor. The choice of Topo Map fits the map to the topography surface. The choice of Moveable Map pops up a slider allowing you to interactively move a flat horizontal map to any pressure level. It is sometimes desirable to display a map at the 100 mb level, particularly when another product obscures the surface topography and map.

Another reason to use the moveable map is to display a map at the same level as a horizontal cross section. This creates a label that appears in the display window, allowing the map to be linked with other cross sections.

Select the Map Color Check Button to pop up a Colors Editor Dialog Box with three sliders labeled red, green, and blue, and a color wheel. To change the map color, just move the sliders.

2.1.6.9 Help

This pull-down menu, shown in Figure 22, provides on-line assistance and information about D3D.

• About...

  Provides the build and release dates of the D3D application software.
  
  

• Users Guide...

  Contents connects you, via Netscape, to the Table of Contents of this D3D On-Line User's Guide.
  
  

• Show Popup Tips

  Provides a check button that enables/disables the Tooltips.
  
  

• For System Developers:

  Memory Use
  
  Memory Use compares the memory requested by D3D with the free system memory. Refer to the D3D Installation Guide for more information.
  
  Vis5D Status...
  
  Status allows you to pop-up a monitor window. The messages contained in the Status Window (discussed in Subsection 2.1.5, "Other D3D Operational Information") may include announcements from the D3D communication software. Warning messages that appear in the Status Window are usually related to data access. Refer back to Figure 5.
  
  Vis5D Interpreter
  
  The Vis5D Interpreter is an entry box for direct communication with Vis5D. This option is used almost exclusively by D3D system developers. Refer to Figure 23.

Figure 23. Vis5D Interpreter.

Vis5D Interface

Provides access to the original Vis5D User Interface control panel. This option is used almost exclusively by D3D system developers.

2.1.7 The Toolbar

2.1.7.1 Load Modes

Load Modes provide different ways to display model or real-time data by manipulating previous model runs and inventories of data sets. Use this pull-down menu to select a mode before loading a model from the Volume Browser. A brief description of each Load Mode follows.



• Latest Run

  This Load Mode displays forecast data only from the latest model run.
  
  

• Previous Run

  This Load Mode displays the previous model run, but does not fill empty frames with older data.
  
  

• Inventory

  Selecting a model from the Volume Browser's Source Pull-Down Menu when the Load Mode is set to Inventory pops up a window showing you a complete inventory listing, from which you can select the model run you want.
  
  

• Analysis Loop

  This Load Mode loads a sequence of model analyses, but no forecasts.
  
  

• dProg/dt

  This Load Mode selects forecasts from different model runs which all have the same valid times. This Load Mode is available only when there are no other products loaded in the Large Display Pane.




2.1.7.2 Scale

From this menu you can choose one of four scales, Northern Hemisphere, North American, CONUS, and WFO. These scales are identical to those used in D2D.

When D3D is first started up, the CONUS Scale is displayed in the Large Display Pane. However, you can use the Scale Option Menu to choose any scale.

Once data have been loaded, changing the scale does not affect the Large Display Pane until you display a new product. It does affect what products are available in the menus. In other words, product availability is scale-dependent.




2.1.7.3 Clear

This button, which turns red when the pointer is over it, clears the Large Display Pane except for the map background and topography.

The selected model remains loaded in memory so new products can be loaded easily.

The entire model is cleared from the display when Clear is selected with Mouse Button 2.




2.1.7.4 Stepping

This set of four menu buttons allows you to Step Backward (<) or Step Forward (>) through multiple frames of data, one frame at a time, or to move immediately to the First (|<<) or Last (>>|) frame in the loop.




2.1.7.5 Loop

This icon button toggles looping in the Large Display Pane. Looping is on when the icon button is a lighter gray color.




2.1.7.6 Loop Properties

This icon button opens the Loop Properties Dialog Box. Identical in behavior to the D2D Loop Properties Dialog Box, except the forward and backward looping (bouncing) is not available. Refer to Figure 25 for a display of the dialog box.

2.1.7.7 Print

This icon button prints the contents of the Large Display Pane on a color or black and white printer. To view or edit the current print values, open the Print Dialog Box by selecting Print from the File Pull-Down Menu, found on the Menu Bar.




2.1.7.8 Viewing Modes

Pressing this icon button causes a pop-up window to appear that describes the functions of Mouse Button 1, 2, and 3, corresponding to the viewing mode that is selected. Refer to Figure 26.

Since there are only three Mouse Buttons available on a mouse and there are up to 10 different Mouse Button functions offered in 3D visualization, the Mouse Button functions vary depending on the Viewing Mode.

Selecting a Viewing Mode redefines how Mouse Buttons 1, 2, and 3 behave in the Large Display Pane, as well as the appearance of the Mouse Cursor. These viewing modes are mutually exclusive; only one can be selected at a time. Figure 2, found in Subsection 2.1, summarizes the many D3D mouse button functions.



• Normal

  Normal Viewing Mode (the default), selected in Figure 30, is used to manipulate the viewing angle. In this Mode use Mouse Button 1, 2, and 3 to are used respectively to rotate, zoom, and pan the data in the Large Display Pane.
  
  
  Rotate
  
  By pressing Mouse Button 1 and moving the mouse while the pointer is in the Large Display Pane, the 3D image can be rotated. At any moment, using Mouse Button 1, you can control only two of the three directions of rotation. However, by releasing and re-pressing Mouse Button 1 you can change your "grip" on the box. With practice you can learn to control the box through a series of mouse moves, releasing and re-pressing Mouse Button 1 between moves. Refer to Figure 27.

Zoom

Pressing Mouse Button 2 and sliding the mouse upward zooms in. This makes the box appear bigger. Sliding the mouse downward zooms out. This makes the box appear smaller.

Pan

Press Mouse Button 3 and move the mouse to translate the 3D Box in the Large Display Pane. This is useful if you want to zoom in to something that is not in the center of the box. Note that the center of rotation for box rotations stays at the center of the screen rather than in the center of the box.



• Slice

  This mode is used to interactively reposition horizontal and vertical cross sections using Mouse Button 3 in the Large Display Pane. To move any cross section, simply point at the cross section's corner with the mouse, press Mouse Button 3 and slowly drag the cross section to a new position. Vertical cross sections may also be moved in a perpendicular motion by "grabbing" the middle of the top or bottom edge and dragging it. Vertical cross sections may be moved in an arbitrary motion by grabbing one top edge corner and dragging it to a new location (see Figures 42 and 48).
  
  

• Probe

  This mode is used to inspect individual grid values by moving a 3D Cursor through the 3D Grid. When Probe mode is selected a 3D Cursor appears in the 3D Box which you can move around using Mouse Button 3. Use the Volume Browser Probe Pull-Down Menu to select specific fields for display in the Large Display Pane. Refer to Subsection 2.4.1.2, "Sampling Techniques - Probe."
  
  

• Sounding

  This mode is used to display a vertical sounding and Skew-T at the location of a moveable vertical cursor. Refer to Subsection 2.4.1.1, "Sampling Techniques - Sounding."
  
  

• Trajectory

  This mode is used for creating and displaying wind trajectories. Vertical displays of up to three other variables may also be added. See Subsection 2.4.2, "Trajectories."
  
  

• Clipping

  This mode is used to clip data out of a scene by interactively repositioning a cross section using Mouse Button 3 in the Large Display Pane. Toggle between the six directions (north, east, south, west, up and down) by clicking Mouse Button 2 in the Large Display Pane.
  
  To move any cross section, indicated by a highlighted box, simply point at the cross section's corner with the mouse, press Mouse Button 3 and slowly drag the cross section to a new position. Vertical cross sections may also be moved in a perpendicular motion by "grabbing" the middle of the top or bottom edge and dragging it. Vertical cross sections may be moved in an arbitrary motion by grabbing one top edge corner and dragging it to a new location.
  
  

• Label

  This mode is used to create and edit text labels to annotate the image in the Large Display Pane. Typically this is used for making presentation graphics. You could add a title, your name, the date, highlight a particular feature of the data, or document the meaning of the data seen in the window.
  
  To enter text labeling mode select the Label option from the Viewing Modes Menu.
  
  To create a text label position the pointer somewhere in the Large Display Pane and press Mouse Button 1. A vertical bar cursor appears at that location and you can now (slowly) type in the text. The Backspace Key can be used to correct errors. When you are finished, press Enter.
  
  To move a text label to a new position, point at it with the mouse, hold down Mouse Button 2 and drag the mouse. As you move the mouse, an outline of the text is dragged with the pointer until you release the Mouse Button.
  
  To delete a text label, point at it with the mouse and press Mouse Button 3. Be careful, you are not asked for verification before deleting a label. Once it's deleted, you can only restore it by retyping it.
  
  Creating a bundle saves any text labels you have made. Refer to Subsection 2.1.6, "The Menu Bar," for information on bundles.



2.1.7.9 Perspective

This option toggles between perspective and orthogonal viewing projections. Perspective viewing adds depth to the 3D Display. The icon changes when the button is pressed.




2.1.7.10 Directional

These options set the Large Display Pane to a top-down view, and a north, south, west, and east directional view, respectively. Pressing Mouse Button 2 on the "T" in the Top-Down View Button resets the zoom factor and perspective values, in addition to resetting a top-down view.




2.1.7.11 Store, Recall, and Clear Views

Storing and recalling views is often used to store a single view point that took time to achieve, allowing you to toggle between it and an overhead perspective.

After moving the 3D Box in the Large Display Pane to a new position, press "S" to store the view. To store additional views, continue to move the 3D Box to a new position and press "S" after each new position. Press "R" to recall and sequentially step through stored view(s).

Pressing "C" clears all stored views while the Large Display Pane remains unaffected.




2.1.7.12 Frames

Use this option menu to select the number of product frames you want loaded. The default is 12 frames. There may be occurrences when you request more frames of data than are available. When this happens, the system sends a message to the Status Bar at the bottom of the Main Display. The D3D Frame behavior differs from D2D in that (1) empty frames are not filled with holder data (time matching) and (2) changing frame count after loading a model has no effect.




2.1.7.13 Line Width

With this menu option you can enlarge or reduce the size of line width on a graphic product. As you increase the value, line width automatically increases. The purpose of this feature is to make text and symbols more visible. A performance degradation is noticed when the value of line width is greater than one.

2.2 Working with Graphic and Image Products

2.3 The Volume Browser

2.3.1 The Volume Browser Dialog Box

• the top area contains the Menu Bar; and
  
• the Data Selection Pull-Down Menus;
  
• the middle area contains the Product List and, when opened, the Property Editor (see Figure 35); and
  
• the bottom area contains the Load Button.

2.3.1.1 The Volume Browser Menu Bar

The pull-down menus in the Volume Browser Menu Bar contain options for controlling the Volume Browser and the products chosen through the Volume Browser.



• File

  There is one option under this pull-down menu. Exit closes the Volume Browser.
  
  

• Edit

  There are four possible selections under this pull-down menu, as shown in Figure 29.

Clear sources

Clear sources, as shown in Figure 29, removes any model sources from the Sources List.

Clear fields

Clear fields, as shown in Figure 29, removes any model fields from the Fields List.

Clear user-defined fields

Clear user-defined fields, as shown in Figure 29, clears variables from all pull-down menus created by using the Variable Maker function. Refer to Subsection 5.1.

Clear probe

Clear probe list, as shown in Figure 29, removes any model products from the Probe Selection List.

Clear all

Clear all, as shown in Figure 29, removes any model sources and fields from the Sources, Fields, and Probe Selection Lists.



• Mode

  There are seven possible selections under this pull-down menu, as shown in Figure 30.
  
  

For additional information, refer to Subsection 2.1.7.8, "Viewing Modes."



• Probe

  This pull-down menu, shown in Figure 31, provides a user-selectable list of fields to probe in the Large Display Pane. The Probe Pull-Down Menu is disabled unless the Viewing Mode is set to Probe.

It is sometimes useful to be able to inspect individual data values at various locations in the 3D volume. When Probe mode is selected a 3D Cursor appears in the 3D Box which you can move around using Mouse Button 3. The selected field's value, for the current time step, is printed along the left edge of the Large Display Pane.



• Help

  This pull-down menu, shown in Figure 32, provides on-line assistance and information about the Volume Browser.

About

Provides the date of the Volume Browser software.

Volume Browser

On Volume Browser connects you, via Netscape, to the Volume Browser subsection of the D3D On-Line User's Guide.

Users Guide

Contents connects you, via Netscape, to the Table of Contents of the D3D On-Line User's Guide.



2.3.1.2 Data Selection Pull-Down Menus

All the data available through the Volume Browser are stored in gridded format and generated as graphic or image products. For each product you display, sources, rendering techniques, and fields are chosen from the menus located in the top third of the Volume Browser.

The many choices of rendering techniques available in D3D sets the D3D Volume Browser apart from the D2D Volume Browser. The rendering techniques available include: isosurfaces; vertical and horizontal cross section contours and images; surface contours and images; and volume visualization (Subsection 2.3.2, "Volume Browser - Rendering Techniques").

The techniques available to sample the gridded data in D3D are a vertical sounding/variable plot and a virtual data probe (Subsection 2.4.1, "Sampling Techniques").

An additional visualization technique displays trajectories (Subsection 2.4.2, "Trajectories").



• Sources

  The Sources Menu, shown in Figure 33, contains numeric models and other gridded data, currently limited to volume radar. This menu is scale-dependent, which means its contents change depending on what scale you choose.

The sequence of selecting items from pull-down menus is order specific, proceeding from left to right. To reinforce this selection order, the Rendering Techniques Menus are disabled until a source is selected.



• Fields

  Once a source is selected, the available data fields are listed in the Rendering Techniques Pull-Down Menus, see Figure 34. Related data fields are grouped together in these menus.

A key interface design for the D3D Volume Browser was to pair field selection with rendering technique selection to create the customized list of products to display, namely the Product List. This eliminates the implicit redundancy in the Product List found, by design, in D2D. With the amount of information present in 3D visualization, it is important to avoid automatically adding products not explicitly requested. Combining rendering technique and field selection explains why the complete list of available fields is found under each rendering technique pull-down menu.



• Selecting a Field

  To display a field as a product, (1) decide on a rendering technique, (2) select that rendering technique pull-down menu, and (3) click on the desired field from the pull-down menu using Mouse Button 1. A product name appears in the Product List. See Figure 34.

2.3.1.3 Using the Product List

Once a field is selected, its product name (composed of a model name, a value, a field name, and the rendering technique) appears in the Product List. By design, products in the Product List are highlighted and ready to load. You can select or deselect the products you want to load pressing Mouse Button 1 over a product name.

Pressing Load generates all highlighted (selected) products for all time steps. The pointer changes to a watch while the system is loading products.

Toggling Looping on allows you to see the time dynamics.

2.3.1.4 The Property Editor

The ability to adjust the properties of a product in the Product List (from their default values) is available through the product's Property Editor. Pressing Mouse Button 3 over a product name in the Product List causes a popup menu (with value, color, and other widgets) to appear at the bottom of the Volume Browser, as illustrated in Figure 35. The product name is also modified to say (*** Edit mode ***) indicating that, currently, this product is being edited.

To close the Property Editor again click on the product name in the Product List with Mouse Button 3. To edit properties on another product from the Product List, you can click on that product name with Mouse Button 3 without having to first close the current Property Editor.

A list of property editors widgets are described as follows.



• Entry Box

  To change entry box values either use the small arrow buttons to increase/decrease the value or type in a value, then press Return using your keyboard when the focus is on the entry box (indicated by a highlighted black box).
  
  

• Slider

  To change the slider value, press and drag the slider to a new value with either Mouse Button 1 or 2. You can also click to a new value with Mouse Button 2. To change the slider amount by a unit of one, click Mouse Button 1 on either side of the slider indicator.
  
  

• Color

  To change the color of a product, press the Set Colors Popup Menu and choose one of the nine colors from the popup menu. If you want more color selection, choose Edit Colors from the Set Colors Popup Menu. A Colors Editor Dialog Box appears with three sliders labeled Red, Green, Blue, and for some products a fourth slider labeled Opacity, and a Color Wheel, see Figure 36.

To change the product color, just move the red, green, and blue sliders or move the Color Wheel Centroid (a circle with a dot in the middle) around in the Color Wheel. To change the opacity, just move the opacity slider to the desired value. Select Apply to color the product, or Close to cancel.

To change the colors of a product colored by a range of color values, choose Edit Colors. You can use this to modify existing color tables, or create new ones and save them for future use. Figure 37 shows the Image Colors Editor.

The Colors Editor Dialog Box

This section describes the features of the Colors Editor. Note that the controls in the upper color portion of the dialog box are mirrored in the lower color portion. The controls in both portions behave the same way.


Color Model

RGB (Red, Green, Blue) Color Model interpolates in a straight line across the Color Wheel from the color in the upper Color Swatch to the color in the lower Color Swatch. The intermediate colors are not included.

RGB Slider Bars

These slider bars allow you to make incremental changes in the hue, saturation, or brightness, or in the amount of red, green, or blue that is present in the color displayed in the Color Swatch. These values can be set using the slider bar or by typing in a value in the entry box to the right of the slider.


Red, Green, Blue

Red, green, and blue values all range from 0 - 255 and reflect the amount, or intensity, of each color present in the displayed color. Changing these values moves the Color Wheel Centroid across the Color Wheel, but not necessarily along a radial.

Opacity

Opacity ranges from 0 to 100 percentage. The higher the value, the more opaque the product appears. The lower the value, the more transparent the product appears.

Color Wheel

The box on the right side of the dialog box contains the Color Wheel. The Color Wheel Centroid (a circle with a dot in the middle) can be dragged anywhere within the circle to change the color displayed in the Color Swatch (more on this later in this subsection). Moving the Centroid around the circle also changes the RGB values.

Brightness

Brightness values are given in percent and determine the amount of black present in the color. Brightness can also be thought of as the intensity of the color.

Color Swatch

To the far right of the Color Wheel is the Color Swatch. Moving the Color Wheel Centroid changes the color in the swatch.

Set

These buttons, located in both the upper and lower portions of the Colors Editor, insert a narrow line of color into the current Color Bar at the location of the Color Pointer. The color inserted is the one displayed in the corresponding (i.e. upper or lower) Color Swatch.

Fill

These buttons replace the colors contained within the range specified by the Color Pointers in the Color Bar with the colors in the upper or lower Color Swatch.

Color Bar

The Color Bar contains the color table of the current image and is located in the middle of the dialog box.

The arrowhead Color Pointers along the top and bottom halves of the Color Bar can be dragged to delineate a range of the color table; that is, the portion of the Color Bar contained between the top and bottom arrows. The Color Pointers move independently of one another, but they cannot move past each other. When aligned, they move in unison and delineate a single point along the Color Bar.

As the Color Pointers are dragged along the Color Bar, they display the image values corresponding to the color pointed to. Thus, for example, if a temperature cross section is displayed, moving the Color Pointer shows the temperature values corresponding to the colors in the Color Bar.

At each end of the Color Bar are left- and right-pointing arrows. These are used to move the Color Pointers along the Color Bar an increment at a time. The > and < Buttons move the Color Pointers in smaller increments than the >> and << Buttons.

Edit Controls

At the bottom of the dialog box are the Edit Controls.


Interpolate

This button fills the specified range with a linear (RGB) interpolation between the colors in the upper and lower Color Swatches.

A linear interpolation is equivalent to moving in a straight line across the Color Wheel.

Blue to Red

This button fills the specified range of the Color Bar with the color spectrum, blue through red inclusive.

Red to Blue

This button fills the specified range of the Color Bar with the color spectrum, red through blue inclusive.

Apply

This button applies the Color Bar changes to the displayed product.

Close

You close the Editor with this button.

Undo

This button allows you to successively undo changes made to the color table.

Redo

This button successively re-does what was last undone.

Revert

This button returns the Color Bar to its original state.

Read...

This button reads a color table from a file completely filling the Color Bar from its minimum value to its maximum value.

Save...

Use this button if you want to save a color table. A dialog box asks you to enter a name for your color table and then lets you save it or cancel the command.



• Load "Technique"

  Press the Load "Technique" Button to generate a product for all time steps after changes have been made.
  
  

• Default Values

  Default Values resets the properties of all the current Property Editor widgets to their original values.

2.3.2 The Volume Browser - Rendering Techniques

2.3.2.1 Isosurface

• Description

  An isosurface is a 3D contour surface of a field at a particular value. It depicts a volume bounded by the value allowing you to visibly see the 3D structure of the field. For isosurfaces with a positive (negative) value, the volume inside the isosurface contains values greater (less) than the isosurface value. Likewise, the volume outside contains values less (greater) than the isosurface value. Refer to Figure 38 for an example of an isosurface.

• Property Editor

  The Isosurface Property Editor, as shown in Figure 39, has several options.

Value

To change the isosurface value move the slider.

Changing Min or Max values causes the extents of the slider (and the color table which maps data values to colors) to reset to these values.

Immediate mode

Select Immediate mode to automatically have changes to any isosurface widget generate a new isosurface for all time steps. Otherwise, press the Load Isosurface Button to generate an isosurface for all time steps after changes have been made.

Color


Set Colors/Edit Colors

To change the color of the solid colored isosurface, press Set Colors Popup Menu and choose one of the nine colors from the popup menu. To invoke the Colors Editor select Edit Colors.

Solid

An isosurface may be either a solid color or colored according to the values of another field. By selecting Solid (default) on the Property Editor's Color section you tell D3D to color the field a solid color and by selecting a name other than Solid, you tell D3D to color the isosurface by another field. To change the colors of this second field, press Edit Colors. An editable color table appears, see Figure 37. You can modify the color table, which maps data values to colors, by using the Colors Editor widgets.

To illustrate coloring one field by the values of another field, load a model of, say, LAPS. Make an isosurface of cloud water at 1.0 g/m*3. Initially, the isosurface would be a solid color. Open the Properties Editor then change Solid to Height. Press Load. The cloud water isosurface is now sampling the height field. Using the color legend as a reference you can more easily determine the height of the clouds. By pressing Edit Colors from Property Editor the Colors Editor appears allowing you to modify the mapping of height values to colors.

For more information, refer to the Color Subsection, described under Property Editor in Subsection 2.3.1.4, "The Property Editor."

Overlays

Isosurfaces that are relatively smooth and have only one value for each horizontal location (typically those of pressure, height, temperature, etc.) can be overlaid with graphic products: wind barbs, streamlines and contour lines. Isosurfaces that meet this criteria are sometimes referred to as a "well behaved" isosurface. Isosurfaces that are inconsistent throughout a 3D grid and are not smooth nor, often, large enough to generate meaningful or intelligible graphic products on their surface such as relative humidity values or divergence, for example, and cannot be overlaid with graphics products.

To overlay a graphic product, select an item from the Overlay pull-down list. The item is immediately entered into the Volume Browser customized list of products to display. The overlay product is labeled to reflect the connection to the isosurface associated with the product. The overlay product's Property Editor is restricted, yet still allows you to set contour interval, minimum, maximum, colors, etc.

You may load multiple overlays to an isosurface. To break the connection select None, or better yet select Clear from the Toolbar.

2.3.2.2 Plan-View

• Description

  Plan-View allows you to look at a horizontal cross section of data. The cross section can be depicted as contour lines or a colored image (or both, as in Figure 40).

• Property Editor

  The Plan-View Property Editor, as shown in Figure 41, has several options.

Interval

You can enter an interval to use between contour lines, decreasing the interval causes denser contour lines to be generated, increasing the interval results in sparser lines. You can specify a range of values (min, max) which causes only contour values between min and max to be drawn.

Level

The initial position for the cross section is the middle of the box that surrounds the data set. The exact cross section location in terms of pressure level is given by a small numeric label near one corner of the cross section (see Figure 48).

To change the plan-view level move the slider. Changes to Level automatically generates a new plan-view for all time steps.

The position of the cross section can also be changed interactively in the Large Display Pane using the mouse. To do so you must first be in Slice mode by selecting the Slice from the Mode Pull-Down Menu.

To move the cross section, simply move the pointer to the cross section's corner, press Mouse Button 3 and slowly drag it to a new position (see Figure 48).

Type

The plan-view can be depicted as contour lines (by default) or as a colored image by selecting contour or image, respectively.

Color

To change the color of the contours, press the Set Colors Popup Menu and choose one of the nine colors from the popup menu. For further information including coloring an image, refer to the Color Subsection, described under Property Editor in Subsection 2.3.1.4, "The Property Editor."

Load Plan-View

Press Load Plan-View to generate a plan-view for all time steps after changes have been made. Again, changes to Level automatically generates a new plan-view for all time steps.

2.3.2.3 Slice

• Description

  Slice allows you to view a vertical cross section of data. The cross section can be depicted as contour lines or a colored image, or both. Refer to Figure 42 for an example.

• Property Editor

  The Slice Property Editor, as shown in Figure 43, has several options.

Interval

You can enter an interval to use between contour lines. Decreasing the interval causes denser contour lines to be generated. Increasing the interval results in sparser lines. You can specify a range of values (min, max) which causes only contour values between min and max to be drawn.

Grid Row/Column

The initial position for the cross section is the middle of the box that surrounds the data set. The exact cross section location in terms of latitude and longitude is given by small numeric labels near one corner of the cross section (see Figure 48).

To change between grid rows and grid columns select the button next to the word Grid. To change the grid row/column move the slider. Changes to row/column automatically generates a new slice for all time steps.

The position of the cross section can be changed interactively in the Large Display Pane using the mouse. To do so you must first be in Slice mode by selecting the Slice from the Mode Pull-Down Menu. This method allows you to position a vertical cross section diagonally if desired (see Figure 48).

Type

The slice can be depicted as contour lines (by default) or as a colored image by selecting contour.

Color

To change the color of the contours, press the Set Colors Popup Menu and choose one of the nine colors from the popup menu. For further information including coloring an image, refer to the Color Subsection, described under Property Editor in Subsection 2.3.1.4, "The Property Editor."

Load Slice

Press Load Slice to generate a slice for all time steps after changes have been made. Changes to Grid Row/Column slider value automatically generates a new slice for all time steps.

2.3.2.4 Volume

• Description

  Volume rendering is a technique for displaying a 3D field as semi-transparent colored fog. Though volume renderings of some fields don't look particularly informative, others can be displayed effectively with the right color mapping. Only one volume may be displayed at a time (unlike isosurfaces).
  
  The volume rendering feature in D3D renders volumes very slowly in software mode (default). Refer to Figure 44 for an example of volume rendering of wind speed.

• Property Editor

  The Volume Property Editor, as shown in Figure 45, has one principle option.

Color

Editing the color table is done exactly the same way as it is for images described in the Color Subsection, under Property Editor in Subsection 2.3.1.4, "The Property Editor." That is, using the pointer or the keyboard arrow keys you can change the function which maps data values to color and transparency. Again, the transparency can be changed while holding down the SHIFT Key and drawing a curve with the pointer or pressing the Up/Down Arrow Keys.

Load Volume

Press Load Volume to generate a volume for all time steps only if the field has changed. Changes to the color table take effect immediately.

Default Values

Default Values do not apply here.

For those who are curious about the implementation of this feature, the volume rendering is made as follows:


1. Examine the current viewing transformation to determine which axis of the 3D Box is most nearly parallel to the view direction.
   
   
2. Create a number of colored slices perpendicular to that axis which map data values to colors and opacity.
   
   
3. Render the colored slices in back to front order. The alpha values at vertices are interpolated and blended to make smooth transitions between and within slices.
   
   Despite the simplicity of the algorithm, most fields are rendered acceptably. Those that aren't might be improved by adjusting the color and opacity mappings. While more attractive volume rendering techniques are known, this technique can be implemented quickly on many systems.

2.3.2.5 Surface

• Description

  Surface allows you to look at data on the 3D topography surface. The surface data can be depicted as both contour lines and a colored image.
  
  To display a field on the topography surface, you first select Surface's Pull-Down Menu, second choose either the Contour or Image Menu, then click on the desired field. Refer to Figure 46 for an example of an image display with contours.

• Property Editor

  The Surface Property Editor, as shown in Figure 47, has several options.

Interval

You can enter an interval to use between contour lines, decreasing the interval causes denser contour lines to be generated, increasing the interval results in sparser lines. You can specify a range of values (min, max) which causes only contour values between min and max to be drawn.

Color

To change the color of the contours, press the Set Colors Popup Menu and choose one of the nine colors from the popup menu. For further information including coloring an image, refer to the Color Subsection, described under Property Editor in Subsection 2.3.1.4, "The Property Editor."

Load Surface

Press Load Surface to generate a surface for all time steps after changes have been made.

2.3.2.6 Winds

Description

Winds allows you to look at horizontal plan views and vertical cross sections of wind data in the 3D volume and at the surface. The wind data can be depicted as wind glyphs (barbs or arrows) and as streamlines labeled Wind and Streamlines, respectively. Wind streamlines show the airflow of wind as connected line segments. To plot winds at the surface choose the Volume Browser's surface rendering technique. Refer to Figure 48 for a wind data display.

Property Editor

The Winds Property Editor, as shown in Figure 49, has several options.

Interval

The Scale value applies only to wind barbs. It is used to multiply the length of vectors. If you want to double the length of all vectors, enter 2.0. If you want to halve the lengths, enter 0.5.

The Density value controls how many wind barbs and streamlines are displayed. In the case of wind barbs the value can only be between zero and one. To make one-half the number of vectors, enter 0.5, for one-fourth enter 0.25, etc. The default value for both is 1.0.

In the case of streamlines the value can only be between 0.5 and 2.0. To make one-half the number of streamlines, enter 0.5, to make twice the number of streamlines, enter 2.0, etc. The default density is 1.0.

To change Scale and Density values either use the small arrow buttons to increase/decrease the value or type in a value then press Return using your keyboard.

Slider

The initial position for the cross section is the middle of the box that surrounds the data set. The exact cross section location is given by a small numeric label near the corner of the cross section (see Figure 48).

To change the value move the slider. Changes to the slider do not automatically generate a new slice for all time steps. The position of the cross section can be changed interactively in the Large Display Pane using the mouse (see Figure 48). To do so you must first be in Slice mode by selecting the Slice from the Mode Pull-Down Menu.

For horizontal winds: To change from displaying Winds at pressure (MB) levels (the default) to displaying them at the surface select the button closest to MB.

For vertical winds: To change between grid rows and grid columns select the button closest to Grid.

Color

To change the color of the contours, press the Set Colors Popup Menu and choose one of the nine colors from the popup menu. If you want more color selection information refer to the Color Subsection, described under Property Editor in Subsection 2.3.1.4, "The Property Editor."

Load Winds

Press Load Winds to generate a winds for all time steps after changes have been made.

2.4 Other 3D Rendering Techniques

2.4.1 Sampling Techniques

2.4.1.1 Sounding

Description

A Skew-T Diagram is generated for gridded data at the location of a vertical cursor. When you select the Sounding viewing mode from the Mode, a vertical sounding pop-up window appears on the screen and a vertical line cursor appears in the Large Display Pane that runs from the bottom to the top of the 3D Box. The location of the sounding can be selected and moved interactively using Mouse Button 3 or using the Put 3D Cursor menu option found in the Tools Pull-Down Menu on the Menu Bar. Refer to Figures 50 and 51 for a sample Skew-T plot and sounding.

You can control the background of the Skew-T Diagram, including dry adiabats, moist adiabats, constant mixing ratio lines and height tick marks by selecting/deselecting the appropriate buttons found under the Skew-T Options menu. The fields, Temp, Dewpt, U, and V are used by default for the Skew-T.

Future enhancements to the sounding will be the ability to plot user-selected parameters, sampled in the vertical column, and the display of derived parameters (e.g. helicity), like those offered by D2D. You can interactively resize and reposition the sounding window, but on some Linux systems this may delay system response for a moment while the X server locates the new position.

2.4.1.2 Probe

Description

It is useful to inspect data values at various locations in the 3D volume. You do this with the probe. Select Probe from the viewing Mode Menu on the Volume Browser Menu Bar. A 3D Cursor appears in the 3D Box. You can move around using Mouse Button 3. The value of each field for the current time step is printed along the left edge of the Large Display Pane. If you toggle the Grid Number option found in Display Options, the probe is constrained to integral grid coordinates. That is, the cursor 'snaps' to the nearest grid coordinate. Refer to Figure 52 for an example of the probe output and the Probe Pull-Down Menu.

2.4.2 Trajectories

1. To position the 3D Cursor, use a combination of rotating the view box with Mouse Button 1 and dragging the 3D Cursor with Mouse Button 3.
   
   
2. Use the VCR Buttons or looping option to select a time step.
   
   
3. Press Mouse Button 2 to create a trajectory at the current cursor location and time step.
   
   
4. To toggle the display of a trajectory set on or off, click on the Set Button with Mouse Button 1.
   
   
5. Select the current trajectory set by clicking on the Set Button with Mouse Button 2.
   
   
6. A trajectory set may be deleted with the Delete Set Button in the Trajectories Dialog Box. You are asked to verify your decision.
   
   
7. You can delete the last trajectory made by clicking on the Delete Last Button in the Trajectories Dialog Box.