Digital Earth > Terravision^TM > User Guide > Tcl/Tk > Settings Menu

The Settings Menu

Dataset Settings

For example, in the screen shot above we can see that the user has loaded 2 datasets into TerraVision and all of these are currently visible. You add or remove a dataset from the view by clicking on its name in the left pane and clicking the "Visibility" button.

You can also alter the priority which is used to display multiple datasets. In other words, the order in which datasets are displayed. For example, if you have a model of the earth and a model of the San Francisco Bay Area, then if you display the model of the earth last it will obliterate the Bay Area model.

Therefore, this dialog lets you interactively change the display priority for all datasets in a particular 3-D viewer. The highest priority datasets (rendered last) appear at the top of this list. For example, in the screenshot above, the Mojave dataset is displayed first, then Monterey Bay is displayed on top of that.

The Z-Buffer Hack option is enabled by default. It provides an interm solution to the problem or rendering datasets embedded within other datasets. Ordinarily, if you were to render two overlapping and nearly co-planar surfaces then you would see a lot of "flimmering" effects. That is, parts of one dataset would jut through the other because of lack of Z-buffer resolution. The Z-Buffer Hack solution basically clears the Z-Buffer (depth buffer) between the rendering of each dataset. This produces a solid and faithful display when looking from above, but can introduce some visual artifacts when close to the ground looking out along the horizon.

The Auto Pop2Front option will let TerraVision automatically set the dataset priority for all datasets, and update this whenever a new dataset is loaded. This works by reordering all datasets so that the highest resolution sets are given higher rendering priority.

Navigation Settings

• Airplane Controls -- toggles the way that the mouse controls pitch. With it checked, moving the mouse away from you pitches down (like an airplane joystick), and vice-versa.

• Height scaled navigation -- when this option is checked, the a user's velocity will be scaled by altitude. This is done in an attempt to maintain a constant visual flow no matter where the user is. For example, without this feature, if you travel at 1000 km/s over terrain then this will appear relatively fast; however, moving through space towards the earth at this speed will be painfully slow.

• Fly To Mode -- when this mode is active, clicking the left mouse button will be treated as a request to fly towards the part of the terrain that you selected.

• 2D Navigation -- when this option is checked, then the viewpoint is always constrained to face straight down and be aligned with the lat/long graticule. In addition, a "Slide" navigation mode is enforced. This in effect gives a pan and zoom type interface. When you select the "Views/2-D Viewer" option from the main TerraVision menu, you are actually opening a 3-D Viewer with this option on by default.

Render Settings

• Terrain Lighting -- toggles the use of lit or unlit geometry and textures.
• HUD -- toggles the display of the heads-up display on the 3-D viewer. This includes a textual display with various useful information about the 3-D viewer process. Note that the Debug Settings option lets you display a more verbose HUD.

• Horizon Culling -- toggles the culling of all tiles that are over the horizon. In effect, this is a special case of occlusion culling for entire earth models so that you don't render tiles on the other side of the planet.
• Wireframe -- toggles wireframe view of tile set.
• Textured -- toggles display of texture data.
• Show Models -- toggles the display of all VRML features.
• Show Ground -- toggles the display of the default earth surface. This will not be required when browsing an entire earth model and will be automatically deselected when browsing entire earth datasets.
• Outline Datasets -- toggles the display of a bounding box around all datasets that are currently loaded, along with a label giving the name of the dataset. This is an extremely useful feature for locating very small datasets that are embedded in the globe.
• Stereo Mode -- toggles the use of stereo mode
• Scale IPD w/Distance -- in stereo mode, this option will scale the inter-pupillary distance with altitude in order to maintain a fused 3-D illusion.

• Popping -- this widget lets you specify how TerraVision managed the progressive display of higher resolution data. TerraVision uses a quadtree structure so that each (non-leaf) tile has four higher resolution tiles. The following options are available:

  1. LowFrag : this option will display all higher resolution children as they are available. For areas of the quadtree where TerraVision has not yet received the high resolution children, it will cut out the correct quarter from the parent tile. Currently, no tile stitching is done between the high resolution tiles and the low resolution fragment so some tearing may be evident temporarily.

  2. LowRes : display the lower resolution parent along with all of the available higher resolution children. This mode can cause some artifacts when children tiles fight between the lower resolution tile for priority.

  3. None : the four high resolution children are displayed all at once and only when they have all completely loaded. This means that higher resolution data is not displayed as soon as it is received. Also artifacts can occur when you move around such that tiles switch to very low resolution because TerraVision has not yet loaded all of the high resolution data for the tiles adjacent to those that were at the edge of the previous view frustum.

• Inter-pupillary Distance (cm) -- this slider lets you alter the distance that TerraVision believes exists between the two pupils of the viewer. This is during stereo mode to control the degree of overlap for the left and right image. Alter this can help users to fuse the stereo image for their visual system.
• Resolution Adjustment -- alters the level-of-detail threshold used to evaluate the number of tiles to display for a particular viewpoint.
• Fog Density -- changes amount of fog.
• Drop to Wireframe Threshold -- TerraVision supports the option to switch to a wireframe terrain rendering when the frame rate drops below a certain threshold. This only occurs while navigating. This option is useful to improve feedback during periods of motion on systems that do not have the computation resources to update the display fast enough. Setting this value to 0.0 will turn the option off.
• Field of View -- changes the solid field of view angle for your viewpoint. (2 to 180 degrees.)
• Elevation Scale -- currently disabled.
• Time of Day -- currently disabled.

3D Model Settings

• Model Lighting -- toggles the use of an additional light for the VRML scene. This light is located at the viewer's location at the time the option is selected. This behaviour will likely change in the future.

• Wireframe Models -- toggles whether all models are displayed in wireframe or solid rendering mode.

• Textured Models -- toggles whether all models will be texture mapped or not. If a model has no textures, then this option will have no visual effect.

• Load Textures -- when on, this option says that whenever you load a new VRML model then you should also load all of its texture maps. When this option is off, then we do not load the textures. This option is useful to speed up loading when you do not care about a textured model.

• Backface Culling -- toggles whether all models are backface culled. Individual models can define whether they have backface culling (e.g. the solid field of the VRML IndexedFaceSet). This option is useful to force all models to backface cull and hence reduce the polygon count, as well as look for any polygons that are facing the wrong way.

Doodle Settings

The doodle on screen option lets you write on the 3-D window using your mouse. The coordinates for the text that you write will be sent to an OAA facilitator for interpretation after the specified timeout delay (only if you are connected to an OAA facilitator, e.g. you used the -oaa command line option). N.B. If you set the timeout to 0, then the text will remain on the screen until you clear it using the "Clear" button.

If the Project to Terrain option option is on, and the Doodle on Screen option is also on, then once you have finished a doodled it will be projected onto the terrain underneath it. This can be used to create temporary annotations directly on the terrain.

Window

The "Show menubar" submenu option can be used to toggle the display of the menu bar at the top of the window. You can also perform this operation by pressing 'M' on the keyboard. The keyboard shortcut is important to know because once you have hidden the menu bar, you cannot access the menu option to bring the menu bar back!

The "Show status bar" option can be used to toggle the display of the status bar at the bottom of the window. This gives you various pieces of information including your current navigation mode and view mode. You can also perform this operation by pressing 'A' on the keyboard.

The "Show logo" option will toggle the display of the SRI logo in the bottom-right corner of the TerraVision window.

Copyright ©2000 SRI International. All rights reserved.

For more information, please contact: digital-earth@ai.sri.com.
Last updated: Friday, 09-Mar-2001 16:01:44 PST.