|
|
IDL Demo Library |
|
The globe demo illustrates a number of features of the IDL language, including texture mapping, model rotations, and the concept of a color palette.
The globe demo illustrates texture mapping, a method of warping images to polygons. The polygons in this demo make up the Earth. Specifically, the datasets are texture mapped onto a sphere object. You can change the texture map that is displayed over the continents or over the oceans.
You can also rotate the globe interactively. Position the cursor on the image and, while holding down the left mouse button, move the cursor to rotate the globe. Release the mouse button when you are satisfied with the position of the globe. This is implemented with IDL's object graphics, including the Trackball object for rotation of the scene.
The globe demo also illustrates the concept of a color palette. A color palette is a color lookup table used to map values (of an image) to red, green, and blue intensities. Temperatures are displayed with colors that range from red to blue and topography is displayed in grayscale. The color palette is divided so that one dataset uses one portion of the color palette and another dataset uses another portion of the color palette.
You can also "stretch" the color palette within the globe demo, which alters only the color palette; image values remain constant. A stretch remaps the red, green, and blue values to new image values. For instance, the red to blue portion of the color palette is mapped to the temperature values. You can shift the color palette associated with temperatures so that red is mapped to lower temperatures. The entire color palette is stretched with this shift. Conversely, one may shift the color palette so that blue is mapped to higher temperatures. Shifting the color palette can accentuate image features. In this demo, you can emphasize regional variability in temperature or topography.
Select "Quit" to exit the Globe Demo and return to the IDL Demo main screen.
Select "Reset Orientation" to return to the initial globe perspective.
Select "About the Globe Demo" for information about the Globe Demo.
Displays either temperatures or topography over the continents.
Displays either temperatures or topography over the oceans.
Stretches the temperature color palette; the color associated with the minimum temperature is shifted to a higher temperature. The entire temperature palette is stretched.
Stretches the temperature color palette; the color associated with the maximum temperature is shifted to a lower temperature. The entire temperature palette is stretched.
Stretches the topography color palette; the color associated with the minimum elevation is shifted to a higher elevation. The entire topography palette is stretched.
Stretches the topography color palette; the color associated with the maximum elevation is shifted to a lower elevation. The entire topography palette is stretched.
IDL Demo Online Help (October 11, 2006)