Digital Earth: TerraVision: User Guide


Topics
•	Getting Started
•	Cmd Line Opts
•	Tcl/Tk Version
	• Navigation
	• File Menu
	• View Menu
	• Settings Menu
	• Paths Menu
	• Links Menu
	• OAA Menu
	• Debug Menu
	• Help Menu
•	X/Motif Version
•	NS Plugin Version
•	ActiveX Version
•	Configuration
•	Creating Data
•	OAA Interface

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Digital Earth > Terravision^TM > User Guide > Tcl/Tk > Navigation

Navigation within TerraVision

Mouse Controls

You can navigate around the 3-D environment using a mouse by moving the cursor into the viewer window and using the mouse buttons as follows. Probably the easiest mode of navigation is the 2-D mode, which is essentially a pan and zoom mode with a constrained, downward looking view.

Middle Mouse Button: In 3-D mode, rotates the current viewpoint as you drag the mouse but does not change your location, i.e. this can be considered analagous to simply moving your head to look around the environment. In 2-D mode, dragging the middle mouse button is analagous to panning over the terrain at a constant elevation. You can also use this button to stop if you are currently moving.
Left Mouse Button: In 3-D mode, accelerates you through the environment. In 2-D mode, zooms into the terrain. You can move the mouse while you are moving forward to change your trajectory.
Right Mouse Button: In 3-D mode, decelerates your forward momentum, eventually moving you backwards through the environment once you reach zero velocity. In 2-D mode, zooms out from the terrain. You can move the mouse while you are moving forward to change your trajectory.

If you depress one of the SHIFT keys on the keyboard, then the behaviour of the mouse navigation changes to give you viewer-centric navigation as follows:

SHIFT + Middle Mouse Button: slides the current viewpoint to the left or right, up or down, depending upon how you move the mouse from the initial mouse click. You can think of this as equivalent to side-stepping or bobbing your head up or down.
SHIFT + Left Mouse Button: accelerates you forward along the direction that you are currently facing. You can move the mouse while you are moving forward in order to slide the viewpoint during the motion.
SHIFT + Right Mouse Button: decelerates your forward momentum, eventually moving you backwards from the way that you are currently facing. Again, you can move the mouse while you are moving forward in order to slide the viewpoint during the motion.

TerraVision emulates the middle mouse button whenever you depress the left and right mouse buttons at the same time. This lets you fully control TerraVision even if you only have a two button mouse.

Keyboard Controls

You can press a number of keys while the mouse is over the Plugin window in order to quickly access a number of features. In order to detect keyboard events under Windows, you may need to first click inside the plugin canvas so that it gains keyboard focus. Currently, the following key strokes are supported:

'O' - return to the default (Origin) viewpoint
'2' - switch to 2-D constrained viewing mode
'3' - switch to 3-D viewing mode
'D' - toggle the display of dataset outlines
'H' - toggle the display of the Heads Up Display
'L' - toggle the display of the SRI logo
'-' - toggle the Z-buffer hack for multiple datasets
SPACE - stop flying
ESC - quit

Heads Up Display

The Heads Up Display (HUD) provides a textual overlay in the bottom-left corner of the display with various useful pieces of information. There are two HUD modes, debug and normal. The debug mode provides a lot more information, while the normal mode provides a more concise readout. The following information is displayed in the debug HUD, with only the first two items being shown under normal circumstances.

The (latitude, long, elevation) of your viewpoint
Your (yaw, pitch, roll) orientation
The effective near and far clipping planes.
The current frame number and the number of tiles in the scene
The 1 second data burst rate into the application (MBit/s) and the total amount of data read so far
The frame rate of the graphics system (instantaneous and averaged over 5 second)

You can toggle the display of the HUD by pressing 'H' on the keyboard, and you can make TerraVision start up with the debug HUD by providing the command line option, -cmd "set(SHOW_HEADS_UP_DEBUG,1)".