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<title>GAMGI Tutorials: Directional and positional lights</title>
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<h1>Directional and positional lights</h1>
<div id="notebook">
<ul>
<li><a href="lights_page1.html">Page 1</a></li>
<li><span>Page 2</span></li>
</ul>
</div>
<div class="contents">
<h3>Shininess</h3>
<ol>
<li>Select <b>Light->Modify</b>, and press the mouse on the drawing area.
A menu pops up, showing two menu items, for the two lights available. After
choosing the first light, confirm its properties, in particular the new light
direction, position, and angle, that were changed with the mouse.
</li>
<li>
Set <b>Specular</b> to <b>(0.6, 0.6, 0.6)</b> and press <b>Ok</b>.
A bright spot is now visible at the center of the atom, due to the
reflected light.
</li>
<li>
Select <b>Light->Config</b> and set <b>Shininess</b> (<b>Materials</b> page)
to <b>0.0</b>. After pressing <b>Ok</b> the bright spot disappears.
Repeat the operation, this time set <b>Shininess</b> to <b>0.5</b>.
After pressing <b>Ok</b> the bright spot reappears, much brighter
now, as the material light reflectance was increased.
</li>
</ol>
<h3>Maximum illumination</h3>
<ol>
<li>Select <b>Light->Modify</b>, and press the mouse on the drawing area.
A menu pops up, showing two menu items, for the two lights available. After
choosing the first light, set <b>angle</b> back to <b>90.0</b>,
color <b>Ambient</b> to <b>(0.6, 0.6, 0.6)</b>, <b>Specular</b> to
<b>(0.0, 0.0, 0.0)</b> and press <b>Ok</b>. The initial full color atom
circle returns.
<p/>
This happens because the absence of lights correspond in fact to
the existence of a light with <b>Ambient</b> component set to
<b>(1.0, 1.0, 1.0)</b>, and <b>Diffuse</b>, <b>Specular</b> components
set to <b>(0.0, 0.0, 0.0)</b>, the maximum luminosity that can be achieved.
As the light components of the two lights are added, the total ambient light
is now (1.0, 1.0, 1.0), so the maximum luminosity has been already reached
and additional diffuse light cannot increase further the luminosity.
</li>
</ol>
<h3>Wired objects illumination</h3>
<ol>
<li>
Select <b>Atom->Modify</b> and press the mouse over the atom. After confirming
the atom properties, set <b>Style</b> to <b>Wired</b> and press <b>Ok</b>.
The atom is now shown as a cross.
</li>
<li>
Press <b>Light->Modify</b> and press the mouse over the graphic area. A menu
pops up, showing two menu items, for the two lights available. After choosing
the first light, confirm its properties, set <b>Ambient</b> to
<b>(0.0, 0.0, 0.0)</b> and press <b>Ok</b>. Repeat for the second light,
so the total ambient light is now (0.0, 0.0, 0.0). Because wired objects cannot
reflect diffuse or specular light, they require ambient light to be visible.
As the ambient light has been switched off, the wired cross becomes barely visible.
</li>
<li>Select <b>Light->Remove</b> and press the mouse over the graphic area.
A menu pops up, showing two menu items, for the two lights available. Choose
the first light, then the second, to remove them. The wired cross is visible
again.
</li>
</ol>
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