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<title>GAMGI Interfaces: Layer Config</title>
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<h1>Layer Config</h1>
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<ul>
<li><a href="config_projection.html">Projection</a></li>
<li><span>Position</span></li>
<li><a href="config_history.html">History</a></li>
</ul>
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Define here the region of space to where the user
is looking by default when creating a new layer.
<p/>
Initially, the user is at (0, 0, +z), looking down to
(0, 0, 0), and the up direction is (0, 1, 0), so the x axis
points to the right, the y axis points to the top, and the z
axis points to the user.
<h3>Eye</h3>
Set the user position, that is applied by default, when creating
a new layer. Any position in 3D space is valid.
<h3>Center</h3>
Set the position to where the user is looking, that is applied by
default, when creating a new layer. The distance from <b>Eye</b>
to <b>Center</b> must be within the limits of visibility (from
<b>Near</b> to <b>Far</b>).
<h3>Up</h3>
Set the direction pointing up, to the top of the screen,
that is applied by default, when creating a new layer. This
direction is converted internally to a unit vector normal to
the direction <b>Eye</b> -> <b>Center</b>, so any non-zero
vector that is not parallel to that direction is valid.
<p/>
The user position and orientation can be defined by a (X,Y,Z)
layer referential, pointing from the middle of the screen to: the
right (X), the top (Y), the user (Z). <b>Eye</b> is the origin,
<b>Eye</b> <- <b>Center</b> defines the Z axis, and <b>Up</b>
the Y axis, permiting to get the X axis by the cross product
of the other two axes. Initially, the axes are orientated along
(1,0,0) for X, (0,1,0) for Y and (0,0,1) for Z, but this is no
longer the case when the layer referential is rotated.
<p/>
Each layer has its own position parameters, so in a window with
multiple visible layers, the image rendered in the graphic area
is the superposition of the various, totally independent, layer
views.
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