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<p><strong>DIRECT SCENE INTERACTIONS</strong>

</p>
</br>
<p />
Viewer interactions with the camera are summarized below. In each case the interaction is listed, along with
description and user actions required to achieve it. 
<p />
 
<img src="cameraInteraction.png" > 

<p /> <ul>
<li> <strong>Note for orthographic cameras</strong>:<br>There is no field of view of view/focal length  dollying and zooming producing an identical               scaling action.<br>               There is a fixed eye direction  so the Orbit` action is disabled.

</li></ul> 
<p /> <ul>
<li> <strong>Note for perspective cameras</strong>:<br>Dollying (moving the camera backwards/forwards) and zooming are often confused, and may               appear very similar.<br>               When you dolly the camera the lens focal length does not change, hence the distortions               associated with the projections are unaffected. However the movement can result in objects               coming through the front` of the camera and disappearing.<br>               When you zoom, the camera does not move  hence clipping of near objects is unaffected.               However with extremely small zooms (FOV large/focal length short) noticeable distortions,               causing straight lines to become curved, can be seen with objects near the camera  the fisheye`               lens effect.<br>               <strong>Generally dollying is more `natural`, but you may need to use both to achieve the desired               perspective and eye position  particularly when you are working inside or very close to 3D               objects</strong>.
</li></ul> 
<p />

<br/>
<p><strong> KEY ACTIONS</strong>
<dl>
</p>
<dd>
       <p>  j          --- zoom in</p>
       <p>  k          --- zoom out</p>
       <p>  Arrow Keys --- pan (truck) across scene</p>
       <p>  Home*      --- reset current camera </p>
</p>
</dd></dl>
*Note: Home key does not exsists on Mac. The same action is created
with 'fn + LeftArrow' keys. 
</br>
<p><strong>MUSE ACTIONS</strong></p>



<p>   You can rotate(orbit) the scene by holding the left mouse button and moving
   the mouse (perspective camera, needs to be enabled for orthograpic camers).
   By default, the scene will be rotated about its center. To select
   arbitrary center selected "PickCameraCenter" in popup context menu.
</p>
<p>   You can pan (truck) the camera using the middle mouse button or arrow keys.
</p>
<p>   You can zoom the camera by dragging side to side holding the right
   mouse button (in perspective mode the camera is translated along viewing axis).
</p>

<p><strong>MODIFIER KEYS FOR ROTATION, PANNING, AND ZOOMING:</strong> </p>
<pre>
   Shift       --  accelerate by factor 10</br>
   Ctrl        --  decelerate by factor 10</br>
   Ctrl+Shift  --  decelerate by factor 100</br>
</pre>




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