* Made Geometry.associate/unassociate To/From GroupNode methods public so they can be GeometryGroupNode implementations outside the com.jme3.scene package

* Added ability to get the geometry start index for GeometryGroupNode implementations

jme3-core/src/main/java/com/jme3/scene/Geometry.java

@@ -81,7 +81,7 @@ public class Geometry extends Spatial {
      * The start index of this <code>Geometry's</code> inside 
      * the {@link GeometryGroupNode}.
      */
-    protected int startIndex;    
+    protected int startIndex = -1;    
     /**
      * Serialization only. Do not use.
      */
@@ -316,7 +316,7 @@ public class Geometry extends Spatial {
      * @param node Which {@link GeometryGroupNode} to associate with.
      * @param startIndex The starting index of this geometry in the group.
      */
-    protected void associateWithGroupNode(GeometryGroupNode node, int startIndex) {
+    public void associateWithGroupNode(GeometryGroupNode node, int startIndex) {
         if (isGrouped()) {
             unassociateFromGroupNode();
         }
@@ -331,13 +331,15 @@ public class Geometry extends Spatial {
      * 
      * Should only be called by the parent {@link GeometryGroupNode}.
      */
-    protected void unassociateFromGroupNode() {
+    public void unassociateFromGroupNode() {
         if (groupNode != null) {
             // Once the geometry is removed 
             // from the parent, the group node needs to be updated.
             groupNode.onGeoemtryUnassociated(this);
             groupNode = null;
-            startIndex = 0;
+            
+            // change the default to -1 to make error detection easier
+            startIndex = -1; 
         }
     }
 
@@ -486,7 +488,7 @@ public class Geometry extends Spatial {
         // but the cloned one is not attached to anything, hence not managed.
         if (isGrouped()) {
             groupNode = null;
-            startIndex = 0;
+            startIndex = -1;
         }
         
         geomClone.cachedWorldMat = cachedWorldMat.clone();

jme3-core/src/main/java/com/jme3/scene/GeometryGroupNode.java

@@ -8,6 +8,20 @@ package com.jme3.scene;
  */
 public abstract class GeometryGroupNode extends Node {
     
+    protected static int getGeometryStartIndex(Geometry geom) {
+        if (geom.startIndex == -1) {
+            throw new AssertionError();
+        }
+        return geom.startIndex;
+    }
+    
+    protected static void setGeometryStartIndex(Geometry geom, int startIndex) {
+        if (startIndex < -1) {
+            throw new AssertionError();
+        }
+        geom.startIndex = startIndex;
+    }
+    
     /**
      * Construct a <code>GeometryGroupNode</code>
      */