WELCOME TO THE VOLUME RENDERING DEMO


This demo shows the fundamentals of volume rendering
using two different data sets.


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

File Menu:

    Select "Quit" to exit the demo and return to the main
    IDL Demo screen.


Edit Menu:

    Select "Gradient shading" to toggle gradient shading
    on and off. Turning gradient shading on shows more
    shading information, but takes longer to render.

    Select "MIP rendering" to toggle the use of
    Maximum Intensity Projection rendering.

    Select "Auto render" to toggle the automatic
    rendering feature. If "Auto render" is on, the
    rendering and and drawing process are executed
    after any change of options. If "Auto render" is
    off, you must manually click the "Render" button
    to render after changing options.

    Select "Left mouse scale" to toggle the ability to
    scale the rendered image. If scaling is on, you can
    click the left mouse button and drag the mouse pointer
    in the draw widget to change the size of the rendered
    image. If scaling is off, clicking and dragging in
    the draw widget rotates the image.

    Select "Color palette tables" to select from a sub-
    menu of color palettes.

    Select "Opacity table" to select from a sub-menu
    of opacity tables.

    Select "Wire box" to toggle the rectangular box drawn
    around the rendered volume on and off.

    Select "Solid plane" to display (or remove) a plane
    intersecting the rendered volume.

    Select "Cursor" to display (or remove) a set of
    orthogonal axes drawn through the center of the
    rendered volume.

    Select "Render step" to select from a sub-menu of
    rendering quality options. Selecting "111" provides
    the highest quality (and the longest rendering time),
    selecting "444" provides the lowest quality (and the
    shortest rendering time).

About Menu:

    Select "About volumes" to display this text.

FEATURES OF THE VOLUME RENDERING DEMO
-------------------------------------

<<Brain>> and <<Bessel>> Radio Buttons
   Select one of these radio buttons to render either
   a human brain or a Bessel function.

<<Render>> Button
   Click on this button to do the rendering computations
   and display the volume.


Rotating the Rendered Volume
   To rotate the rendered volume, position the mouse
   pointer in the draw widget, hold down the left 
   mouse button, and drag the mouse. If you have the
   "Auto render" feature turned off, you will need
   to click the "Render" button after you have
   rotated the volume. If you have the "Left mouse
   scale" feature turned on, clicking and dragging
   in the draw widget will scale the rendered
   volume rather than rotating it.