Digital Earth > Terravision^TM > User Guide > X/Motif > "Views" Menu > The 3-D Viewer > "Options" Menu

The 3-D Viewer "Options" Menu

Navigation Options The Navigation Options widget lets you control a number of attributes of the TerraVision system that relate to how you the user can interact with the data. The following options can be controlled from this window. 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. 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. 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. Doodle on Screen -- 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. Project to Terrain -- when this 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.

Render Options The Render Options widget lets you control a number of attributes of the TerraVision system that relate to how the data are displayed. The following options can be controlled from this window Check boxes: 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. Mipmap -- toggles the use of mipmaps for texture-mapping. Mipmapping is a technique for improving the display of textures, and can greatly reduce "swimming effects" that happen at low incident angles. Wireframe -- toggles wireframe view of tile set. Textured -- toggles display of texture data. Show Models -- toggles the display of all VRML features Show Clouds -- toggles the display of the clouds texture map when you are close to the ground Show Ground -- toggles the display of the ground plane. This will not be required when browsing an entire earth model. 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. 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. 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. Selections: 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: 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. 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. 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 are 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. Sliders: 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 Elev Scale -- changes the scale of the elevation data, allowing you to exaggerate vertical heights for improved visual effect Field of View -- changes the solid field of view angle for your viewpoint. (2 to 180 degrees.) Fog Density -- changes amount of fog. Time of Day -- changes lighting to simulate time of day.

Debug Options The Debug Options dialog contains a number of features that have been useful in debugging the 3-D Viewer of TerraVision. However, they are also useful for demonstrating how TerraVision works. Freeze Tiles -- for every frame, TerraVision works out the smallest subset of tiles that it requires for that viewpoint by culling against the view frustum and employing lower resolution tiles farther from the viewer. This option let's you freeze the tile selection that TerraVision made for a particular view. You can then fly around and examine this tile subset to see how TerraVision performs its optimizations. It is useful here to turn on the view frustum display and the tile bounding boxes via the Link menu. The "Return to Frozen View" button will reset the viewpoint to the location and orientation when you turned the Freeze Tiles feature on. Debug Tiles -- this option will display a wireframe overlay over every tile in order to show the polygonal structure for each tile. The colour used for each adjacent tile is changed in order to show tile boundaries more clearly. Also, a different pair of colours is used for tiles at different resolution.

Feature Selection The Feature Selection dialog lets you control the loading and display of VRML models that can be overlayed on the terrain. The list view in the window displays all of the VRML models that are available for the set of GeoSets that have been loaded. You can load a model by clicking on the toggle button before its name. The "Info" button is used to display various metadata in the text window at the bottom of the dialog. The toggle widgets on the right side of the dialog have the following behaviour: Textured -- toggles whether all models will be texture mapped or not. If a model has no textures, then this option will have no visual effect. 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 -- toggles whether all models are displayed in wireframe or solid rendering mode. 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 Cull -- 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.

Dismiss Selecting this option will close the current 3-D Viewer window. You can also achieve this by pressing 'Esc' on the keyboard, or by double-clicking on the window's close widget in the top-left corner.

Copyright ©2000 SRI International. All rights reserved.

For more information, please contact: digital-earth@ai.sri.com.
Last updated: Friday, 09-Mar-2001 15:51:19 PST.