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<title>GAMGI Interfaces: Light Create</title>
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<h1>Light Create</h1>
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<ul>
<li><span>Geometry</span></li>
<li><a href="create_color.html">Color</a></li>
<li><a href="create_attenuation.html">Attenuation</a></li>
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Define here the geometry of the new light.
<h3>Directional</h3>
Directional lights emulate lights very far from the objects they
illuminate (as the Sun illuminating the Earth), so: 1) the light
beams can be considered as paralel; 2) the attenuation produced
by the distances between the objects is negligible, compared to
the attenuation produced by the distance from the source (the
intensity of the Sun light iluminating the top of a building
or a street nearby is approximately the same).
<p/>
Directional lights are thus determined by the <b>x</b>,
<b>y</b>, <b>z</b> coordinates of the <b>Direction</b> vector.
<h3>Positional</h3>
<b>Positional</b> lights emit from a single point into all directions,
with equal intensity. The attenuation in the beam intensity, from the
source to the objects might be already significant (the visibility
produced by street lights decreases rapidly with distance).
<p/>
Positional lights are thus determined by the <b>x</b>, <b>y</b>,
<b>z</b> coordinates of the light <b>Position</b>.
<h3>Spot</h3>
Spot lights differ from positional lights because they emit in a given
<b>Direction</b>, as in a lamp. The <b>Angle</b> (beam aperture) between
this <b>Direction</b> (the spot) and the light outer limit (the cutoff),
can vary between almost 0 degrees (as in a laser) and 90 degrees (as in
a ceilling light).
<p/>
A spot light is thus determined by its position, direction and angle.
<p/>
<b>Direction</b>, <b>Position</b>, <b>Angle</b> and <b>Attenuation</b>
entries are automatically enabled or disabled, according to the type of
light selected.
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