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<H1><A ID="SECTION00530000000000000000">
Depth of Field</A>
</H1>
<P>
Under many circumstances,
it is desirable to render
objects in the image such that they are in sharp
focus on the image plane. This is achieved by using the default
``pinhole' camera. In this mode, the camera's aperture is a single
point, and all light rays are focused on the image plane.
<P>
Alternatively, one may widen the aperture in order to
simulate depth of field. In this case, rays are cast from various places on
the aperture disk towards a point whose distance from the
camera is equal to the
<#244#><EM>focus distance</EM><#244#>. Objects that lay in the focal plane will be
in sharp focus. The farther an object is from the image plane,
the more out-of-focus it will appear to be.
A wider aperture will lead to a greater blurring of
objects that do not lay in the focal plane.
When using a non-zero aperture radius, it is best to use jittered
sampling in order to reduce aliasing.
<P>
<DL>
<DT><STRONG><#4658#><#4658#></STRONG></DT>
<DD><#1219#><TT>aperture</TT><#1219#> <#1220#><EM>radius</EM><#1220#>
<BR> Use an aperture with the given <#248#><EM>radius</EM><#248#>.
</DD>
</DL>The default radius is zero, resulting in a pinhole camera model.
<P>
<DL>
<DT><STRONG><#4659#><#4659#></STRONG></DT>
<DD><#1223#><TT>focaldist</TT><#1223#> <#1224#><EM>distance</EM><#1224#>
<BR> Set the focal plane to be <#253#><EM>distance</EM><#253#> units from the camera.
</DD>
</DL>By default, the focal distance is equal to the distance from the
camera to the look point.
<P>