World Rotation Tool

The World Rotation Tool creates animated views of rotating map
projections.  Images can be warped on to any of nine different
projections.

The World Rotation Tool accepts an image as an argument. 

Select the "SPIN" button to create an new 
animation.  The new animation frames will be drawn
one by one into an animation window.  When all of 
the frames have been drawn, the new animated "movie"
will be shown.  Only one animation can be displayed
at a time.  To create another animation, select 
"End Animation" from the animation window, adjust any
options, and select "SPIN" again.

To use a different image, select the "Get a New Image"
button.  A list of available images will appear.  Select
one and the list of images will go away.  Adjust any options
and select the "SPIN" button to see the new image in all of
its animated glory.

To quit the World Rotation Demo, select "Done".



The World Rotation Tool options are described below:

Select the type of projection to use from the "Map
Projections" menu. The buttons below the Projections 
menu select continent drawing, grid drawing, and bilinear 
interpolation options.

Select "Draw Continents" to draw continent outlines over 
the map projection.

Select "Draw Grid" to draw latitude and longitude lines
over the map projection.

Select "Bilinear Interpolation" to smooth the color 
gradients in the warped image. The default is no 
interpolation.

The "Longitude Sampling" and "Latitude Sampling" sliders
control the number of points from the original image that
MAP_IMAGE uses make the warped image.  Higher values create
higher resolution warped images that take longer to draw.

The "Latitude to be Centered" slider controls the 
"viewing angle" in the latitude direction. The default
is 0 latitude. Choose 90 or -90 for polar projections.

The "Rotation of North" slider controls the angle of
rotation of the North axis. The default is 0 degrees.

The "Continent Color" slider controls the color of the
continent outlines.

The "Grid Color" slider controls the color of the grid lines.

The "Animation Window Size" fields control the width and
height of the animation frames in pixels. Larger values 
provide higher resolution, take longer to draw, and use 
more memory.

The "Number of Frames" slider selects the number of
equally-spaced frames to use in the animation.  Larger
numbers of frames make the animation look "smoother" but 
also take more time and memory.

The "Messages" window provides instructions and status
messages.

This super-cool widget application was created by RSI's
Keith R. Crosley using the IDL/widgets graphical 
user interface toolkit. 

Keith is a documentation guy, not a 
professional programmer. If he can write a widget, 
you can too! Examine the file WORLDDEMO.PRO if you want
to see the simple code that created this widget application.

    August, 1991