terrain will clear any caches it has now when detached from the scene graph

git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@10424 75d07b2b-3a1a-0410-a2c5-0572b91ccdca

engine/src/terrain/com/jme3/terrain/geomipmap/TerrainPatch.java

@@ -982,5 +982,27 @@ public class TerrainPatch extends Geometry {
         return worldTranslationCached;
     }
 
+    /**
+     * Removes any references when the terrain is being removed.
+     */
+    protected void clearCaches() {
+        if (leftNeighbour != null) {
+            leftNeighbour.rightNeighbour = null;
+            leftNeighbour = null;
+        }
+        if (rightNeighbour != null) {
+            rightNeighbour.leftNeighbour = null;
+            rightNeighbour = null;
+        }
+        if (topNeighbour != null) {
+            topNeighbour.bottomNeighbour = null;
+            topNeighbour = null;
+        }
+        if (bottomNeighbour != null) {
+            bottomNeighbour.topNeighbour = null;
+            bottomNeighbour = null;
+        }
+    }
+
 
 }

engine/src/terrain/com/jme3/terrain/geomipmap/TerrainQuad.java

@@ -1807,6 +1807,34 @@ public class TerrainQuad extends Node implements Terrain {
         return quadClone;
     }
         
+    @Override
+    protected void setParent(Node parent) {
+        super.setParent(parent);
+        if (parent == null) {
+            // if the terrain is being detached
+            clearCaches();
+        }
+    }
+    
+    /**
+     * Removes any cached references this terrain is holding, in particular
+     * the TerrainPatch's neighbour references.
+     * This is called automatically when the root terrainQuad is detached from
+     * its parent or if setParent(null) is called.
+     */
+    public void clearCaches() {
+        if (children != null) {
+            for (int i = children.size(); --i >= 0;) {
+                Spatial child = children.get(i);
+                if (child instanceof TerrainQuad) {
+                    ((TerrainQuad) child).clearCaches();
+                } else if (child instanceof TerrainPatch) {
+                    ((TerrainPatch) child).clearCaches();
+                }
+            }
+        }
+    }
+    
     public int getMaxLod() {
         if (maxLod < 0)
             maxLod = Math.max(1, (int) (FastMath.log(size-1)/FastMath.log(2)) -1); // -1 forces our minimum of 4 triangles wide