3D Visualization
Perhaps GeoVirgil's most exciting feature is the 3D visualization. With it, you can fly around another world. To create the 3D window, simply go to the main menu bar, select "3D View" and then "Create".
Eventually, the 3D view will appear:
There are two ways to fly around Mars. One is to plug in a USB joystick and the other is to use the Flight Controls Panel. Here's what the control panel looks like;
At the bottom of the panel is the Pitch Modifier. Use this control to tilt the eye point up or down. For example, when flying around if you can't see the horizon you might want to move the slider to the right.
The final major control on this panel is "Sensor". This determines if data from a sensor layer is combined with the imagery to create the 3D view. GeoVirgil starts out just showing the black and white imagery. By changing the "Sensor Mode", you can colorize the imagery based on its elevation or thermal inertia or albedo.
The colors selected for elevation is NASA's MOLA colorization scheme, which is shown below. It uses shades of blue for the lowest values, followed by shades of green, red and eventually white. This same color scheme is also used to colorize other sensor data. So, if you are in Thermal Inertia Mode, regions with a low thermal inertia (that is, where the ground changes temperature more easily) are tinted in blue and regions with higher thermal inertia are tinted white.
You can a USB joystick to pilot your "virtual spaceship". The buttons on the joystick can be used instead of the buttons on the 3D Control Panel. The buttons function as follows:
Button 1 (typically the trigger) Higher
Button 2 Lower
Button 3 Slide Left
Button 4 Slide Right
Button 7 Sensor to Visual
Button 8 Sensor to Elevation
Button 9 Sensor to Thermal Inertia
Button 10 Sensor to Albedo
Virtual Mars Construction Options
You can easily construct a virtual Mars by simply selecting 3D View -> Create. However, you can also specify in some detail how the 3D world should be built. This is especially important if the default options create a virtual world too slow to run efficiently on your computer.
Here's what each option controls:
Tile Entire Globe. When selected, GeoVirgil tiles the entire globe in elevation and sensor data. When not selected, GeoVirgil only creates the section of the virtual globe defined by loaded Viking imagery data. Turning this option off will create a virtual world that can be quickly created, efficiently rendered on computers not fast enough to handle an entire world.
Exaggerate Elevation Factor. GeoVirgil takes the actual elevation data of the surface of Mars to create the hills and valleys in the 3D view. To make topology easier to see, you can exaggerate the height and depth of features. GeoVirgil defaults to an exaggeration factor of 5 so all slopes are shown 5 time steeper then they actually are. If you want an accurate surface, change the elevation exaggeration factor to 1. If you want small changes in elevation to be obvious, plug in a large value.
Include Thermal Inertia, Albedo and Elevation Sensors. The 3D view can colorize high resolution imagery with sensor data and tile the globe with sensory data. If you need to simplify the virtual world GeoVirgil creates, you can disable any or all of these virtual sensors.
Include Background Layer. GeoVirgil's map contains a low resolution background image for nearly all of Mars. This data can be used cover the 3D world with imagery. By default, this option is on but if you need to increase performance it can be turned off.
Include False Sky. With this option you can control whether on not GeoVirgil creates a sky. The exact sky color on Mars is a matter of intense debate which I will work hard to avoid. I picked a color there seemed to be strong support for but have not researched all the issues. Note that sky color doesn't change as you fly higher. This isn't realistic, but if the color at the surface is still debated, the color at altitude is probably less well understood.
Screen Saver Mode. If enabled and there is no user flight input for 20 seconds the computer will start flying around the planet. When you engage a flight input (either joystick on a button on the Flight Control Panel), screen saver mode is terminated and you are again in control.
Views Of Mars
Once the 3D world has been created, you are free to fly around and explore. Here's a view from an high above Mars:
If we continue to fly higher, the image soon becomes:
This image is from an altitude of 3800 km and shows almost half of Mars. It clearly shows the high resolution imagery covered only a small part of the globe. On a computer less than a year or so old, you should have no trouble creating a globe like this flying around it.
Changing Terrain
Once you create the 3D world it takes whatever high resolution imagery is loaded into the map view and applies it to the globe. If you then load in more imagery (by, for instance, clicking on the Adventure button) the new data won't appear in the 3D view. Unfortunately, once you create the 3D world it does not change. If you want to the high resolution imagery in a larger or different area, you have to first exit GeoVirgil, then load in the desired data and finally create the 3D world.