/*
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* Bone.java
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*
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*
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* The Salamander Project - 2D and 3D graphics libraries in Java
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* Copyright (C) 2004 Mark McKay
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* Mark McKay can be contacted at mark@kitfox.com. Salamander and other
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* projects can be found at http://www.kitfox.com
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*
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* Created on March 10, 2004, 8:54 AM
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*/
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import javax.media.j3d.*;
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//import javax.vecmath.*;
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import java.util.*;
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/**
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* <p>Bones define a skeleton that is linked to a SmoothMesh. By repositioning the
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* bone joins, one can deform it's associated mesh.</p>
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*
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* <p>A bone coordinate system can be thought of as similar to a regular TransformGroup
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* hierarchy within the scene graph, with the exception that mesh verticies are
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* transformed instead of instanced geometry and that a vertex can be influenced
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* by more than one bone. To transform a mesh from it's bind pose (starting position)
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* to it's animated pose, you need to perform a weighted sum of the effects that
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* each bone contributes to the point.</p>
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*
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* <p>A single bone transforms points from the local bind coordinate system (static mesh)
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* to the local target coordinated system (animated mesh). Given:</p>
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* <ul>
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* <li/>ltp - local target point
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* <li/>lbp - local bind point
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* <li/>B - bind matrix
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* <li/>A - current joint orientation matrix
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* </ul>
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*
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* <p>then <code>ltp = A B^-1 lbp</code></p>
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*
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*
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* <p>To determine the true transformation a bone contributes to a point, one must
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* take into account the transformations of it's parents too. So if this bone
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* is at level n and n - p indicates it's pth parent, then the true
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* transformation matrix is</p>
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*
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* <code>M = A(0) B^-1(0) ... A(n - 1) B^-1(n - 1) A(n) B^-1(n)</code>
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*
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* <p>The position of the final animated mesh is a weighted sum over all bones.</p>
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*
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* <code>
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* tp = 0 <br/>
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* foreach (joint j) <br/>
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* { <br/>
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* tp += w(bp, j) * M(j) * bp <br/>
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* } <br/>
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* </code>
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*
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* <p>where
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* <ul>
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* <li/>bp - bind point
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* <li/>M(j) - transform of bone j
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* <li/>w(bp, j) - weight for point bp on bone j
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* </ul>
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* </p>
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*
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* @author kitfox
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*/
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public class Bone extends TransformGroup {
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/** Bind transfrom of this bone */
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final Transform3D bindXform = new Transform3D();
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/** Inverse bind transfrom of this bone */
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final Transform3D bindInvXform = new Transform3D();
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/** Current local pose position of this bone */
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final Transform3D animXform = new Transform3D();
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final Vector<Bone> children = new Vector<Bone>();
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/** Creates a new instance of Bone */
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public Bone(Transform3D bind)
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{
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super(bind);
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bindXform.set(bind);
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bindInvXform.invert(bind);
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animXform.set(bind);
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setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
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}
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/**
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* Adds a child bone to this one.
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* @return - index of added child
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*/
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public int addChildBone(Bone child)
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{
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if (children.contains(child)) return children.indexOf(child);
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super.addChild(child);
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children.add(child);
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return children.size() - 1;
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}
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public void addChild(Node child)
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{
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if (child instanceof Bone)
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{
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addChildBone((Bone)child);
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}
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else super.addChild(child);
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}
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public int getNumChildBones() { return children.size(); }
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public Bone getChildBone(int idx)
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{
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return (Bone)children.get(idx);
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}
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/**
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* Returns cached bone xform. Do not write to this matrix! Instead, call
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* setTransform to update this bone's orientation
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*/
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public void getTransform(Transform3D xform)
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{
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xform.set(animXform);
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}
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public void getBindTransform(Transform3D xform)
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{
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xform.set(bindXform);
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}
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/**
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* Updates the animated local transformation of this bone
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*/
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public void setTransform(Transform3D xform)
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{
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super.setTransform(xform);
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animXform.set(xform);
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// sceneXformDirty = true;
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}
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public void setToBindTransform()
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{
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super.setTransform(bindXform);
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animXform.set(bindXform);
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// sceneXformDirty = true;
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}
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public Node cloneNode(boolean forceDuplicate)
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{
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Bone bone = new Bone(bindXform);
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bone.duplicateNode(this, forceDuplicate);
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return bone;
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}
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/*
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public void duplicateNode(Node originalNode, boolean forceDuplicate)
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{
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Bone src = (Bone)originalNode;
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}
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*/
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}
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