LIGHT(6D) LIGHT(6D)
NAME
light - demonstrates real-time lighting and shadows
SYNOPSIS
/usr/demos/light
DESCRIPTION
Light displays a cube floating above a grid. The cube is
lit up and casts a shadow on the grid. The mouse valuators
and buttons control the display.
To change the display, press the right mouse button to
display a popup menu. Move the cursor until the menu option
you select is highlighted and release the button. To get
rid of the menu without changing the display, move the cur-
sor clear of the menu and release the button.
Automatic operation
Select the window for input. Press and hold the right mouse
button. A menu appears. Move the cursor to the menu entry
for the desired mode and release the right mouse button.
The cube spin option makes the cube rotate by itself. The
scene spin option makes the scene rotate by itself.
Any automatic motion will continue with the system unattend-
ed.
The label on the menu is the operation that will be executed
if that item is selected. It is not showing what state the
demo is in. This means that if the menu says cube spin on ,
selecting this will turn the automatic cube spin on. It
does not mean that the spin is currently on.
Manual operation
In this demo, the controls are a little different than are
found in most of the others. The controls were designed to
make smooth motions.
With the automatic scene spin off, holding the left mouse
button down will make the scene spin according to the posi-
tion of the mouse. Moving the mouse left makes the scene
spin clockwise; to the right, counterclockwise. Moving the
mouse up makes the scene spin toward you; downwards, away
from you. The farther you move the mouse pointer away from
the center of the screen the faster it spins in the
coresponding direction.
With the automatic cube spin off, holding the middle mouse
button down will control the cube in a similar manner.
Holding the left and middle mouse buttons down at the same
time will make the scene move closer or farther away depend-
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LIGHT(6D) LIGHT(6D)
ing on the position of the mouse. Moving the mouse up will
make the scene move away, down will make it move closer.
MTV mode
This is named after "Music Television" because it is similar
to a video effect commonly used in that sort of thing. In
MTV mode the picture on the screen itself becomes an object.
It can be moved around in the same way as the scene. First
get good at moving the scene around. Then select MTV mode
on the popup menu. Press the left and middle mouse buttons
and move the mouse pointer above the middle of the screen to
back away from the picture a little. Spin the picture by
holding the left mouse button down and positioning the mouse
in the direction you want the picture to rotate.
The automatic cube and scene spin still work while in MTV
mode. Getting out of MTV mode reverts the mouse control
back to what's `inside' the picture. You can make the scene
fill the whole window again by selecting the reset view op-
tion. The S, C and M keys do the same thing as selecting
scene spin, cube spin and MTV mode on the popup menu. One
last trick: when you are in MTV mode and you hold the left
mouse button down to spin the picture, you can press the M
key to get out of MTV mode. The picture will still spin at
the rate you left it.
move lights/stop moving lights
There are two light sources that may be moved independently.
When you select move lights the left and middle mouse but-
tons are used to move the 1st and 2nd light sources. Hold-
ing down the left mouse button and moving the mouse moves
the 1st light source, likewise holding down the middle mouse
button moves the 2nd light source. Selecting stop moving
lights reverts mouse control back to the scene.
reset lights
The light sources are both in the same position when the
program begins. This option returns the light sources to
that initial position. This is handy if you lose track of
the lights while moving them with the move lights option.
reset view
This option resets the view when selected. This is handy for
displaying the scene normally after using MTV mode.
Pressing ESC or selecting kill exits the program.
WINDOW MANAGER
Light only runs in the window manager. Notice that the win-
dow can be made any shape. The scene inside automatically
corrects for the aspect ratio. In MTV mode reshaping the
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LIGHT(6D) LIGHT(6D)
window also reshapes the picture. Even if you detach from
the window, objects in automatic motion do not stop.
COLOR MAP USAGE
In a fully equipped demonstration unit with at least 24 bit
planes, there is enough room in the color map for the colors
used in the light program and the other programs in our demo
package. When running on a unit with only 16 bit planes,
the colors used by light are shared with other programs.
Therefore, on a 16 bit plane machine, use light with no oth-
er graphics windows running. After exiting light, run
demomakemap before displaying other demos. The colors will
not work on a system with less than 16 bit planes.
AUTHOR
Thant Tessman
HARDWARE REQUIREMENTS
Sixteen bitplanes and 2 Megabytes of memory are necessary.
ORIGIN
Silicon Graphics, Inc.
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