rayintersection.html

J2ME Mobile3D API,高性能手机3D开发的api

<DD><p>Retrieves the picked Mesh or Sprite3D object. Other types of
 Nodes are not pickable and hence can not be returned by this
 method.</p>
<P>
<DD><DL>

<DT><B>Returns:</B><DD>the picked Mesh or Sprite3D object</DL>
</DD>
</DL>
<HR>

<A NAME="getRay(float[])"><!-- --></A><H3>
getRay</H3>
<PRE>
public void <B>getRay</B>(float[]&nbsp;ray)</PRE>
<DL>
<DD><p>Retrieves the origin (ox oy oz) and direction (dx dy dz) of the pick
 ray, in that order. The ray origin and direction vector are specified in
 the coordinate system of the Group node where the <code>pick</code>
 method was called from. The returned direction vector is the same that
 is used to compute the distance measure from the pick point to the
 object in <code>getDistance</code>.</p>

 <p>Note that if the application itself provides the pick ray origin and
 direction to the <code>pick</code> method, this method simply returns
 the same information; in particular, the direction vector is returned
 as is, not normalized. On the other hand, if the application uses the
 other <code>pick</code> method, where only a Camera and a point on the
 viewing plane are specified, the ray origin and direction would not
 otherwise be readily available.</p>

 <p>This method together with <code>getDistance</code> enables the point
 of intersection to be computed conveniently, as shown in the example
 below.</p>
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>ray</CODE> - a float array to fill in with the pick ray origin
        and direction, in that order
<DT><B>Throws:</B>
<DD><CODE>java.lang.NullPointerException</CODE> - if <code>ray</code> is null
<DD><CODE>java.lang.IllegalArgumentException</CODE> - if <code>ray.length &lt; 6</code><DT><b>Example:</b><DD><div class="example_title">Computing the ray intersection point.
 
 </div><pre class="example"> <span class="example_type">float</span> x, y, z;                  <span class="example_comment">// the intersection point</span>
 <span class="example_type">float</span> [] ray = <span class="example_reserved">new</span> <span class="example_type">float</span>[6];    <span class="example_comment">// ray origin and direction</span>
 <span class="example_class">RayIntersection</span> ri = <span class="example_reserved">new</span> <span class="example_class">RayIntersection</span>();
  
 <span class="example_comment">// Pick through the center of the viewport</span>
  
 <span class="example_control">if</span> (myGroup.pick(-1, 0.5f, 0.5f, myCamera, ri) == <span class="example_literal">true</span>)
 {
     ri.getRay(ray);
     x = ray[0] + ray[3] * ri.getDistance();
     y = ray[1] + ray[4] * ri.getDistance();
     z = ray[2] + ray[5] * ri.getDistance();
 }</pre></DD></DD></DL>
</DD>
</DL>
<HR>

<A NAME="getDistance()"><!-- --></A><H3>
getDistance</H3>
<PRE>
public float <B>getDistance</B>()</PRE>
<DL>
<DD><p>Retrieves the distance from the pick ray origin to the
 intersection point. The distance is normalized to the length of
 the given pick ray (1.0 = ray length). The length of the pick
 ray is defined as sqrt(dx<sup>2</sup> + dy<sup>2</sup> +
 dz<sup>2</sup>), where (dx dy dz) is the direction vector of
 the ray. The direction vector itself can be obtained using
 <code>getRay</code>.</p>

 <p>The normalized distance is convenient, because it is independent of
 the transformations of the intersected Node and its ancestors, including
 any non-uniform scales and other non-length preserving transformations.
 The distance to the intersection point can be used for simple collision
 detection, for instance.</p>
<P>
<DD><DL>

<DT><B>Returns:</B><DD>normalized distance from the pick ray origin to the intersection
         point</DL>
</DD>
</DL>
<HR>

<A NAME="getSubmeshIndex()"><!-- --></A><H3>
getSubmeshIndex</H3>
<PRE>
public int <B>getSubmeshIndex</B>()</PRE>
<DL>
<DD><p>Retrieves the index of the submesh where the intersection point is
 located within the intersected Mesh. This allows the application to
 identify, for example, the texture image that is displayed at the
 intersection point. The submesh index is only applicable to Meshes;
 its value is always set to zero if the picked object is a Sprite3D.</p>
<P>
<DD><DL>

<DT><B>Returns:</B><DD>index of the intersected submesh (always 0 for sprites)</DL>
</DD>
</DL>
<HR>

<A NAME="getTextureS(int)"><!-- --></A><H3>
getTextureS</H3>
<PRE>
public float <B>getTextureS</B>(int&nbsp;index)</PRE>
<DL>
<DD><p>Retrieves the S texture coordinate at the intersection point
 on the picked Mesh or Sprite3D. For meshes, there can be between
 zero and N texture coordinates, where N is the number of
 texturing units supported by the implementation. If a texturing
 unit is disabled, the corresponding texture coordinates are
 undefined. For sprites, there is always exactly one pair of
 valid texture coordinates (at index zero); the rest of the
 coordinates are undefined.</p>

 <p>If the picked object is a Mesh, the returned coordinates
 represent the texture coordinates <i>after</i> applying the
 texture transformation and projection, but <i>before</i>
 possible clamping. In the case of a Sprite3D, the returned
 coordinates are always between [0, 1], where (0, 0) is the
 upper left corner of the sprite image. Note that the sprite
 crop rectangle has no effect on the returned values.</p>
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>index</CODE> - index of the texturing unit to get the texture
        coordinate of
<DT><B>Returns:</B><DD>the S texcoord of the specified texturing unit at the
         intersection point
<DT><B>Throws:</B>
<DD><CODE>java.lang.IndexOutOfBoundsException</CODE> - if <code>index != [0, N]</code> where
         <code>N</code> is the implementation specific maximum texturing
         unit index</DL>
</DD>
</DL>
<HR>

<A NAME="getTextureT(int)"><!-- --></A><H3>
getTextureT</H3>
<PRE>
public float <B>getTextureT</B>(int&nbsp;index)</PRE>
<DL>
<DD><p>Retrieves the T texture coordinate at the intersection point on the
 picked Mesh or Sprite3D. See <A HREF="../../../javax/microedition/m3g/RayIntersection.html#getTextureS(int)"><CODE>getTextureS</CODE></A> for more
 information.</p>
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>index</CODE> - index of the texturing unit to get the texture
        coordinate of
<DT><B>Returns:</B><DD>the T texcoord of the specified texturing unit at the
         intersection point
<DT><B>Throws:</B>
<DD><CODE>java.lang.IndexOutOfBoundsException</CODE> - if <code>index != [0, N]</code> where
         <code>N</code> is the implementation specific maximum texturing
         unit index</DL>
</DD>
</DL>
<HR>

<A NAME="getNormalX()"><!-- --></A><H3>
getNormalX</H3>
<PRE>
public float <B>getNormalX</B>()</PRE>
<DL>
<DD><p>Retrieves the X component of the surface normal at the
 intersection point. The normal is specified in the coordinate
 system of the intersected Node, and is always unit length. If
 the picked object is a Sprite3D, the normal vector is always
 (0 0 1). If the object is a Mesh with no vertex normals, the
 returned normal is undefined.</p>
<P>
<DD><DL>

<DT><B>Returns:</B><DD>the X component of the surface normal at the intersection point</DL>
</DD>
</DL>
<HR>

<A NAME="getNormalY()"><!-- --></A><H3>
getNormalY</H3>
<PRE>
public float <B>getNormalY</B>()</PRE>
<DL>
<DD><p>Retrieves the Y component of the surface normal at the
 intersection point. See <A HREF="../../../javax/microedition/m3g/RayIntersection.html#getNormalX()"><CODE>getNormalX</CODE></A> for
 more information.</p>
<P>
<DD><DL>

<DT><B>Returns:</B><DD>the Y component of the surface normal at the intersection point</DL>
</DD>
</DL>
<HR>

<A NAME="getNormalZ()"><!-- --></A><H3>
getNormalZ</H3>
<PRE>
public float <B>getNormalZ</B>()</PRE>
<DL>
<DD><p>Retrieves the Z component of the surface normal at the
 intersection point. See <A HREF="../../../javax/microedition/m3g/RayIntersection.html#getNormalX()"><CODE>getNormalX</CODE></A> for
 more information.</p>
<P>
<DD><DL>

<DT><B>Returns:</B><DD>the Z component of the surface normal at the intersection point</DL>
</DD>
</DL>
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<EM><B>Nov 19, 2003</B></EM></EM>
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