Working with the 3D Viewer: 
Most
amateur astronomers have never had the opportunity to use a 3D Viewer, so the
concept may take a bit of getting used to.
Going through the learning curve is well worth the effort though, because
once you become skilled at creating 3D images, you will be able to display and
print your favorite lunar features in a way that has never before been possible
for lunar observers.
IMPORTANT:
The 3D Viewer utilizes extensive
amounts of radar elevation data to create true 3D imagery. The computational complexity of this function
requires considerable computer resources.
Depending upon your system resources, it may take a while to get your
results. Attempting to use the 3D Viewer
on a computer with a severe lack of system resources may overtax and crash the
application.
Click to activate the 3D Viewer. The viewer is
designed to display the topography of selected portions of the lunar surface in
3D. At activation, several viewing
parameters are initialized, and the portion of the lunar surface that is
displayed in the map view is also displayed by the 3D Viewer.
The 3D Viewer
allows users to independently control the map viewing parameters. By using the controls, it is possible to
alter the 3D view in such a way that correspondence with the original map view
is lost. Each time the 3D Button
(or related menu item) is clicked, the viewing
parameters are reset, and correspondence with the primary map is restored.
Choosing the Standard or High Resolution Display
When the 3D Viewer
is first activated, the standard resolution window is the default display. For users with moderate speed computer
systems, this is the preferred setting, since it requires the least amount of
system resources, and produces results more quickly.
If you own a high speed, computer system, you may prefer
working with the high resolution display.
At high resolution, the size of the 3D display window is doubled, as is
the amount of detail visible in the 3D imagery.
To switch to the high resolution display, click the View Menu then click High
Resolution. A check mark will
appear, and the display window will increase in size. Clicking again, removes the check mark and
returns the display to standard resolution.
Viewing Parameter Definitions
The 3D Viewer utilizes several viewing
parameters that directly affect the appearance of the lunar surface being
displayed. These parameters are
introduced and defined below. There are five distinct viewing parameters, as
follows:
·
Point-of-View the line of sight from the
observer's eye to a point on the lunar surface.
That point is always centered in the 3D Viewer window directly below the position of the user.
·
Magnification the visual effect due to the
distance (along the line of sight) of the observer to the surface of the
moon. At the minimum magnification, the greatest
possible surface area that can be seen at once a hemisphere is displayed in
the 3D Viewer window.
- Orientation the tilt of the surface about the center point,
i.e. where the line of sight passes through the surface. This parameter determines whether the
portion of the surface displayed in the 3D Viewer window is seen from directly overhead or at some
other oblique angle.
- Relief Exaggeration a multiplying factor
applied to all surface elevations.
This can be used to help bring out more subtle surface details.
- Visual
Appearance Wire Mesh/Realistic. The wire
mesh appearance shows the basic geometric construction of the surface,
with shading that is consistent with light from behind the observer. The realistic
appearance is derived from optical imagery that is draped over the
wire mesh surface. The light and
shading is derived from the actual imagery. The 3D
Viewer provides controls for all of these parameters.
Viewing Parameter
Initialization
Each
time the 3D Button (or menu item) on the map displays tool bar
is clicked, the point-of-view, magnification, and orientation are set, so that
the 3D Viewer displays roughly the
same portion of the lunar surface that is displayed in the map view. (The 3D Viewer always starts out with North Up, regardless of the setting
used on the primary map.) On the first
click only, the relief exaggeration is set to a default value
that is pleasing to the eye, and the visual appearance is set to wire
mesh. If 3D Viewer controls are used to change either the relief
exaggeration or the visual appearance, these will not be reset on
the next click.
In the
following example, note the difference in the appearance of Clavius
as seen on the primary map, and in the 3D
Viewer window. The reason for the
difference is that the primary map is showing Clavius
as seen from earth (at high magnification), while the 3D Viewer is showing Clavius as seen from directly overhead.
As a
result of the proximity of Clavius to the southern
limb, the primary map is displaying the crater at a highly oblique angle. You will find that as you zoom
in on features that are further from the center of the primary map, the
differences between the two views will become increasingly more pronounced.
If you
zoom in on a region far from the center (without first changing the
point-of-view, so you are directly over the center of the region of interest),
line of sight creates an oblique angle with the surface. If the 3D
Button (or menu item) is then clicked, this same
region will be repositioned in the 3D
Viewer, but the point-of-view of the observer will move directly over the
center of the region.
Further Discussion on Parameters
If the 3D Viewer Tool Bar Controls are used to
change the point-of-view and/or magnification, the correspondence, which exists
initially, between the primary map view and 3D view is lost. In other words, the primary map view does not
automatically adjust to changes you make in the 3D Viewer. To maintain
proper correspondence at all times, change the point-of-view and/or
magnification on the map view, and update the 3D Viewer by clicking the 3D
Button on the main Tool Bar.
Wire Mesh vs.
Realistic Appearance
The wire
mesh appearance is the default because it can be rendered much faster than the
realistic appearance. If you plan to
modify any of the other viewing parameters in steps, it is much more efficient
to do it with the wire mesh view, and then switch to the realistic appearance
at completion. Switch back to the wire
mesh view again before making another series of adjustments. You may want to follow this procedure whether
making adjustments via the 3D Viewer
controls or the map view, unless you have a very powerful computer.
It is
often virtually impossible to recognize a region when using the wire mesh
appearance, if that region is seen from directly overhead, and is sufficiently
small, so that lunar curvature is negligible.
That is because there is no appreciable shading, and there are no visual
clues. Under these circumstances, the
realistic view makes it possible to identify your location. The following overhead views of the
Copernicus Region, in both wire mesh and realistic view, illustrates this
point.
As you
can see, the realistic appearance provides sufficient visual clues so you can
identify the region being displayed, and generally provides a sense of
topographic relief, regardless of the orientation.
As you
view topographic features at an increasingly oblique angle, they become
increasingly easier to recognize in wire mesh mode due to the improved shading
conditions. To illustrate this point,
the Copernicus Region is displayed once again, in both wire mesh mode and
realistic mode, but at a far more oblique viewing angle.
There
may occasionally be situations where the wire mesh appearance shows the relief
more clearly than the realistic appearance.
Orientation vs. Magnification
There
are two ways to see topographic features in true relief. When using high magnifications to view small
regions, it is appropriate to use orientation controls to make the line of
sight oblique. At low magnifications,
with the line of sight directly overhead, topographic features that are
increasingly far from the line of sight are seen at increasingly oblique
angles, due to the curvature of the lunar surface.
When an
entire hemisphere is visible in wire mesh mode, only the most extreme
topography, such as tall mountains and deep craters and valleys, near the edges
of the hemisphere, will be seen in relief.
To understand this, keep in mind that the height of even the tallest mountains
is still hundreds of times smaller than the horizontal distance across a lunar
hemisphere.
As you
can see in the following examples, it is far more difficult to recognize what
you are looking at if the orientation controls are used at low magnification. As the viewing angle becomes increasingly
more oblique, more of the curved surface moves below the horizon. In wire mesh mode, that portion will be seen
through the foreground mesh, and will be completely shaded, (because it is
totally hidden from the light source behind the observer). Since the shading is the same color as the
foreground mesh, it obscures any foreground relief.
To avoid
confusion, follow these guidelines:
1. First
view an entire hemisphere without adjusting the orientation from the overhead
position.
2. As the magnification is increased, you can
make the line of sight increasingly more oblique.
3. If the image becomes confusing, decrease the obliquity,
or switch to the realistic appearance.
Menu items (Controls)
The 3D Viewer provides the user with
controls for all viewing parameters.
They are collected into menus and button groups according to
function. In addition, an integrated control
panel (discussed later), can be used
to provide finer control.
Point of View Controls
The
observer's point-of-view can be modified by clicking on any of four items under
the Point-of-View Menu Rotate North, Rotate South,
Rotate East and Rotate West, or any of these four corresponding toolbar
buttons. 
.
Each
click on a menu item or corresponding button moves the point-of-view along the
curvature of the sphere of the moon, in the indicated direction. With each click, the moon is rotated by 25%
of the angular distance across the portion of the surface that is visible in
the window.
For
example, if an entire hemisphere is on display, the angular distance across the
surface is 180 degrees. A single click
on any menu item or button will shift the point-of-view 45 degrees in the
indicated direction. If the
magnification is such that the angular distance across the visible surface is
say, 20 degrees, then a single click will shift the point-of-view by 5 degrees,
and so on.
Whenever
a Point-of-View toolbar button is
used, your point-of-view moves to a point directly above the feature that is
centered in the 3D Viewer window,
just as if you were looking down on that feature from an orbiting spacecraft.
Magnification Control
The magnification
can also be modified by clicking Zoom-In
or Zoom-Out, under the Magnification Menu, or by using the two corresponding toolbar buttons. 
. Each click on the Zoom-In Menu Item or
corresponding button, (the button with the arrows pointing inward), increases
the magnification by a factor of two.
Each click on the Zoom-Out Menu Item or corresponding button, (the
button with the arrows pointing outward), decreases the magnification by a
factor of two.
When an
entire hemisphere is displayed in the window, the magnification is at its
minimum value. In this situation,
clicking the Zoom-Out Menu Item or corresponding button, will
have no effect.
Orientation Controls
Using
the orientation controls is when the fun really begins. The 3D map orientation can be modified by
clicking on any of the four items under the Orientation Menu, or by
clicking on the Rotate-Up, Rotate-Down, Rotate-Left or Rotate-Right
toolbar buttons.
Each click
on a menu item or corresponding button rotates the surface 10 degrees about its
center, in the indicated direction.
(Alternatively, one can imagine that the line of sight is rotating 10
degrees in the opposite direction.)
The
phrase Rotate Up means a rotation of
the surface about a horizontal line through the center of the view. The top of the surface moves inward (away
from the observer), while the bottom moves outward. The phrase Rotate Down means a rotation about the same horizontal line, but in
the opposite direction. The phrase Rotate Left means a counter-clockwise
rotation about a line perpendicular to the center of the view. The phrase Rotate Right means a clockwise rotation about the same
perpendicular line. These clockwise and
counter-clockwise rotations operate in the same manner even if one or more
rotate up operations has occurred first.
Starting
from the initial state, in which the observer is looking directly down on the
center of the region, the surface can be rotated a maximum of 80 degrees left
or right, and/or 80 degrees up.
OVERHEAD
VIEW OF CRATER, CLEOMEDES
Clicking on the Rotate-Up 
toolbar
button provides an oblique 3D View of the area, (as shown). Clicking on the Rotate-Down 
toolbar
button is used to reverse the process.
Once you
have created a 3D View, you can use the Rotate-Left
or Rotate-Right 
toolbar buttons to change the viewing
angle of the feature. The toolbar
buttons each rotate the map in opposite directions.
The
surface cannot be rotated down, unless it is first rotated up. Once an orientation limit is reached, clicking
the corresponding menu item or button has no effect.
Relief Exaggeration Controls
The
relief exaggeration can be modified by clicking on either of two items under
the Relief Factor Menu, or either of two corresponding
toolbar buttons. 
Each click on the Increment Menu Item, or corresponding toolbar button, 
increases the relief exaggeration.
Each
click on the Decrement Menu Item, or corresponding toolbar
button, 
decreases the relief exaggeration.
The
relief factor may be decreased until there is no exaggeration at all, or it may
be increased to a maximum value of 15 times normal. Once one of these limits has been reached, clicking
the corresponding menu item or button will have no effect.
Visual Appearance Controls
The
visual appearance, (wire mesh vs. realistic), can be modified by clicking on
either of two items under the Appearance
Menu Wire Frame and Realistic,
or either of the two corresponding toolbar buttons. 
.
If the
appearance is currently wire mesh,
clicking the Realistic Menu Item, or
the corresponding button, 
results in a switch to the realistic
appearance. If the appearance is
currently realistic, clicking on the Wire
Mesh Menu Item, or the corresponding toolbar button, 
causes a switch to the wire mesh appearance.
Control Panel
If you are interested in more precise 3D
Viewer control, the Control Panel
provides sliders for: Point-of-View,
Magnification, Orientation, and Relief
Exaggeration. Each slider has tic marks at regular
intervals and an associated text box (on the right) that indicates the actual
value of the viewing parameter for the given pointer position.
On the Point-of-View and Orientation Sliders, the
tic marks are at 10-degree intervals. On the Zoom
Factor and Relief Factor Sliders, the tic marks represent
single-unit steps in the factor size.
The control limits are marked above the sliders, at each end.
Each of
the sliders makes it possible to set particular values for all the
corresponding viewing parameters at one time, rather than in several
increments, as with the menu or toolbar controls. In addition, all but the Relief Factor Slider
provides much finer control of the image than the menu or toolbar
controls.
The Point-of-View can be set to any
latitude and/or longitude desired, rather than just those that are associated
with a 25% shift. The Orientation can be set to any values in
the permitted ranges, rather than just increments of 10 degrees. The Zoom
Factor can be set to any integer value between 1 and 16, rather than just
the powers of two that are possible with the menu or toolbar controls.
If you
click on any of the Tool Bar Buttons or
Menu Items, the corresponding
sliders and text boxes on the Control
Panel will adjust to correspond to the changes. To close the Control Panel, click the box containing 
in the upper-right-hand corner. Anytime the Control Panel is opened or reopened, the settings will reflect the
current state of the 3D Viewer.
Printing and Copying 3D Images
If you
click on the File Menu in the 3D
Viewer, you will be provided with three options.
Copy
If you click Copy, the
image in the 3D display will be copied to your clipboard. You can then open a program such as Microsoft
WordTM,
and paste the image to your documents.
Just open the Edit File in the new document, and click Paste.
This feature comes in handy, when you want to include graphics in your
written documents.
Write Image
If you click Write Image you can save the 3D
display, as a JPEG Image. This is a
useful feature when you want to create a folder of images for later use. JPEG Images can also easily be placed into
documents, or sent over the Internet.
Clicking Write Image displays the Save As Dialog Box. The Save
in Window will generally display your WindowsTM Temp Directory as the
default file folder. The default file
name is Image.jpg.
To store an image in a folder, name the image in the File name Window, and click the Save Button.
Print 
Clicking Print or clicking the Printer Icon will open your Printer
Dialog Box, and allow you to print a hard copy of the 3D Image in the viewer.
Once you
have mastered the 3D Viewer
features, it will be possible for you to create, print, and copy 3D images of
lunar features, such as those shown in the examples below.
The
Theophilus and Cyrillus
Plato and the Alpine (
