www/j3d1_4/vsg-op.html


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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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  <title>Java 3D 1.4: ViewSpecificGroup View Set Operation</title>
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<body>
<h2>Java&nbsp;3D<sup><font size="-2">TM</font></sup> 1.4:
ViewSpecificGroup View Set Operation<br>
</h2>
<p>This page describes a possible enhancement to Java&nbsp;3D 1.4 to
allow the application to specify the operation used to compute the set
of views for nested
ViewSpecificGroup (VSG) nodes. Currently, the set of views used to
render descendants of nested VSG nodes is the intersection of the set
of views
inherited from its
parent(s) and the set of views specified in the child VSG node. We
propose to
add an attribute to VSG such that the resulting set of views is either
as the intersection or the union of the set of views inherited from its
parent(s) and the set of views specified in the child VSG node, or
simply the set of views specified in the child VSG node. More formally,
we plan to define three modes as follows:
</p>
<ul>
  <table border="0" cellspacing="2" cellpadding="2">
    <tbody>
      <tr>
        <td><code>INTERSECT</code></td>
        <td><code>:</code></td>
        <td><code>viewSet[n]
=
viewSet[n-1] &#8745; VSG[n].viewSet</code></td>
      </tr>
      <tr>
        <td><code>UNION</code></td>
        <td><code>:</code></td>
        <td><code>viewSet[n]
=
viewSet[n-1] &#8746; VSG[n].viewSet</code></td>
      </tr>
      <tr>
        <td><code>REPLACE</code></td>
        <td><code>:</code></td>
        <td><code>viewSet[n]
=
VSG[n].viewSet</code> </td>
      </tr>
    </tbody>
  </table>
  <br>
where <code>n</code> is the nesting level (the number of ancestor VSG
nodes in the
scene graph path).<br>
The default mode is <code>INTERSECT</code>.
</ul>
<p>Note that the set of views used to render descendants of a top-level
VSG node (that is, a VSG node that is not itself a descendant of
another VSG node) is the set of views specified in the VSG node,
regardless of the mode. More
formally: <code>viewSet[0]&nbsp;=&nbsp;VSG[0].viewSet</code> for all
values of <code>viewSetOp</code>.<br>
</p>
<p>The proposed API is:</p>
<ul>
  <li>New methods in existing classes:<br>
  </li>
  <ul>
    <pre>ViewSpecificGroup<br>    method: setViewSetOp(int op) // one of: INTERSECT, UNION, REPLACE<br></pre>
  </ul>
</ul>
<ol>
</ol>
<p><font color="gray">Page last updated &#8212;
$Date$
</font></p>
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