ENVIRONMENTAL MODELING
       LEAKY UNDERGROUND STORAGE TANKS

This demonstration is an Environmental Modeling application
that shows the leakage from an array of underground storage
tanks. The display has the following features:

Bore Holes
----------
A series of bore holes were drilled into a test site to 
sample two contamination values in the soil. These contaminants 
are called Element 1 and Element 2. The bore holes are 
represented in the visualization using colored polylines,  
with the colors derived from the values of element 1 along the 
bore hole. The bore hole data is then stored as an irregular 
grid of values, which are read into IDL and gridded using
IDL's 3D gridding routines. This produces a 3D array of data
values on a regular uniform grid.

  
Contamination Plume
-------------------
The 3D volume is used to compute 3D contours (isosurfaces) 
given a contour level (isosurface level) for a particular 
element. This contour level is controlled by the slider under 
the "Isosurface Controls".  When the contour is generated, 
you can choose to use Element 1 or Element 2 for the isosurface
to represent a contamination plume for the specified value. 
You can also choose to compute colors based on a different
contaminant. This allows the user to view the relationship
between the two elements at the same time.

Notice that when selecting the same element for both the 
Isosurface and the Colors, that the resulting surface is a 
constant color.

The high and low values are the laboratory test results.

Tank Geometry
-------------
The storage tank geometry is generated using the IDL function 
MESH_OBJ to create a surface of revolution given a profile 
curve. The output of MESH_OBJ is then used to create IDL
Object Graphics IDLgrPolygon objects, which represent the
individual storage tanks.

You can rotate the display by positioning the mouse
in the draw widget, holding down the left mouse button,
and dragging the mouse.

MENU OPTIONS
------------

File Menu:

    Select "Quit" to exit the demo.

Isosurface Menu:

    Select "Flat" or "Gouraud" from the "Shading" sub-menu
    to alter the type of shading used in displaying the
    contamination plumes.

    Select "Wire" or "Solid" from the "Style" sub-menu to
    alter the surface representation of the contamination
    plumes.

View Menu:

    Select an item from the "Show Object" sub-menu to 
    toggle display of that object on and off in the 
    display area.

    Select "Low" or "High" from the "Drag Quality"
    sub-menu to change the appearance of the display
    during rotation. Selecting "Low" will increase
    the speed of rotation operations. This setting
    only affects the quality of the image during
    rotation.
    
    Select "Reset Orientation" from the "Reset" sub-menu
    to restore the display to its original orientation.

About Menu:

    Select "About Environmental Modeling" to display this
    help text.

FEATURES OF THE ENVIRONMENTAL MODELING DEMO
-------------------------------------------

    The following graphical user interface elements
    allow you to control the demo.

<<Element Selections Radio Buttons>>
    
    Select one button from the "Isosurface" button group
    to display the isosurface contours for either Element1
    or Element2. 

    Select one button from the "Shaded Colors" button
    group to display the concentrations of the selected
    element using color.
    
    Note that if the same element is selected from both
    the "Isosurface" and "Shaded Colors" groups, the surfaces
    will be a single color. If different elements are 
    selected, the concentration of the element selected
    in the "Shaded Colors" button group is overlaid on
    the isosurface data for the other element.

<<Isosurface Controls Slider>>

    Adjust this slider to adjust the value used to determine
    whether a given location is contaminated or not. If the
    value of the specified element at a given location is
    higher than the value of the Isosurface slider, that
    location will appear within the isosurface.