WELCOME TO SURFACE DEMO


This demo shows a the graphic capabilities of a
an IDL Object Graphics surface object. These include:
 - texture mapping,
 - point picking,
 - tracing,
 - masking (or transparency), 
 - interactive change of orientation,
 - vertex coloring,
 - hiding.

You can rotate the surface 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 demonstration.

Options Menu:
    Select "Flat" or "Gouraud" from the "Shading"
    sub-menu to change the way IDL handles lightsource
    shading on the surface.

    Select an option from the "Style" sub-menu
    to change the way the surface is rendered.
    Note that the "Lego Solid" option may take
    a few seconds to render.

    Select a skirt height value from the "Skirt"
    sub-menu to choose between different values of
    the "skirt" that surrounds the object.

    Select "Low," "Medium," or "High" from the
    "Drag Quality" sub-menu to change the way the
    surface is rendered during rotation. This setting
    does not affect the rendering quality of the
    surface when you are _not_ rotating it.

    Select an option from the "Tracing" sub-menu
    to select a "region of interest" in the surface
    and then display only that region. To select
    a region, do the following:

     i)   Select "Trace Mode" (the menu item should
          change to "Trace Mode (on)"). This enables
	  the tracing selection mode.

     ii)  Select one or more regions by clicking
          the right mouse button on the corners of
	  the regions. The boundaries of the regions
	  are indicated by red lines.

     iii) Select "Trace Mask" (the menu item should
	  change to "Trace Mask (on)"). The display
	  now shows only the selected region.

     iv)  To remove the trace mask, select "Trace
	  Reset" (the menu item should change to
	  "Trace Reset (on)"). This removes the
	  red lines marking your region of interest.

     v)   Select "Trace Mask" (the menu should change
	  to "Trace Mask (off)"). This will redisplay
	  the entire surface.

    Select "Hidden" to remove points or lines that are
    "behind" other points or lines in the rendered
    surface. Hidden line removal is computationally
    expensive, and is not done by default. This option
    is only available if you have selected "Point,"
    "Wire," or "Lego Wire" from the Style sub-menu.

    Select "Vertex Colored" to toggle the display between
    showing the surface with a specific color at each
    vertex and showing the surface in a single color.

    Select "Texture Mapping" to toggle the overlay of
    an image on the solid surface.

    Select "Line Style" to toggle the display between
    solid and dashed lines. This option not available
    when the surface is rendered as a solid or using
    points.

View Menu:

    Select "Animate" to display a short animation of
    the surface being warped.

    Select "Reset Orientation" to restore the surface
    to the original orientation in space.

About Menu:

    Select "About Surface Objects" to display this help
    text.

FEATURES OF THE SURFACE DEMO
----------------------------

<<Minimum Slider>> 
    Adjust this slider to select the minimum value 
    to be rendered. Data smaller than this value will
    not be displayed.

<<Maximum Slider>> 
    Adjust this slider to select the maximum value 
    to be rendered. Data larger than this value will
    not be displayed.

<<Scaling slider>>
    Adjust this slider to scale the size of the surface
    between 75% and 125% of its original size.