Use this properties page to control the display of stars and the Earth atmosphere in the 3D Graphics window.
Earth Atmosphere
STK displays the Earth's atmosphere, including fog on terrain, by default in the 3D Graphics window. You can control the visibility of the atmosphere and the fog density using the following options.
Show Atmosphere. To stop displaying the atmosphere in the 3D Graphics window, clear this check box.
Fog Density. Use the slider to control the density of the fog. Move the slider to the left to decrease the density and to the right to increase it. To stop displaying fog, move the slider all the way to the left.
Stars
Celestial Imagery
STK Celestial Imagery is a photographic backdrop of the night sky for use with STK. It enhances the visual impact of space and improves realism when making movies and snapshots. The STK Celestial Imagery data sets are on the STK Data Disc page of the AGI website.
Star display options
Use the following options to control the display of stars in STK.
| Option | Description |
|---|---|
| Show | Select this check box to have STK display stars in the 3D Graphics window. STK selects this by default. |
| Show as Points | Select this check box to have STK display stars at an infinite distance. When selected, you can specify a star collection and adjust Point Display Options. |
| Collection Name |
Specify the star collection to be used as the source of star information for the 3D graphics display. The default of Use Scenario Setting tells STK to use the collection specified on the Scenario->Basic->Database properties page (set Database Type to Star). Use of this setting is a simple way to ensure consistency across two or more 3D Graphics windows. If none of the existing star collections meets the display requirements, click Create… to create a new star collection or to modify the configuration of existing star collections other than those delivered in STK. Selecting an extremely large star collection (> 1 million stars) for display purposes can lead to STK running out of memory and crashing. |
| Show as Texture | Select this check box to have STK display the celestial texture map in the 3D Graphics window. When you select this, you can either enter a filename or click the ellipsis and browse to and select the name of a celestial texture map file (*.ctm). |
Point Display Options
If Show as Points is selected, STK will use the Point Display Options to determine the relationship between the visual magnitude of the stars and the size and translucency of the points used to represent them. You can control the star graphics by specifying the desired settings for typical bright, medium, and dim stars using the following parameters:
| Parameter | Description |
|---|---|
| Magnitude | Represents the brightness of the stars. |
| Point Size | Represents the size of the displayed star in pixel space. |
| Translucency | Values vary from 0, completely opaque, to 100, completely transparent. |
| Colorize Stars | Select this check box to apply a false colorization to stars based on the star effective temperature. For a description of how STK determines the effective temperature, refer to Construction of the STK Star Catalogs. |
The actual representation of a specific star is determined based on interpolation/extrapolation of the provided settings. The brightest star, Sirius, has a visual magnitude of approximately -1.46, while the dimmest star will depend upon the selected star collection. The dimmest stars visible to the naked eye on a clear night have a visual magnitude of about 6.
- The range of visual magnitudes for the currently selected collection is displayed.
- Increasing the size of stars is useful when capturing 3D frames using high resolution.
The celestial image takes precedence over other textures in the texture cache, so once the cache is full, textures on the globe may not render and areas of the globe may appear blurry.