letely outside the viewport, NIL is returned.
</DD>
</DL>
<BR>
<BR>

<P>
	<BR> 
<A NAME="35957"></A>
<BIG CLASS="XLARGE"><B>viewport </B></BIG> [class]  <PRE><TT>
  :super   <B>coordinates</B> 
<BR>  :slots 		 () 
</TT></PRE>
<BR>
<BR>

<DL COMPACT>
<DT> 
<DD>viewport transformation maps the NDC (normalized device coordinates)
 to device specific coordinates.
Inheriting the <B>coordinates</B> class, the <TT>viewport</TT> defines
the size and the relative position of the projection screen.
</DD>
</DL>
<BR>
<