TerrainGrid documentation patch thanks @slyh

git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@9325 75d07b2b-3a1a-0410-a2c5-0572b91ccdca

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

@@ -55,54 +55,56 @@ import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ThreadFactory;
 import java.util.logging.Level;
-import java.util.logging.Logger;
-
-/**
- * TerrainGrid itself is an actual TerrainQuad. Its four children are the visible four tiles.
- * 
- * The grid is indexed by cells. Each cell has an integer XZ coordinate originating at 0,0.
- * TerrainGrid will piggyback on the TerrainLodControl so it can use the camera for its
- * updates as well. It does this in the overwritten update() method.
- * 
- * It uses an LRU (Least Recently Used) cache of 16 terrain tiles (full TerrainQuadTrees). The
- * center 4 are the ones that are visible. As the camera moves, it checks what camera cell it is in
- * and will attach the now visible tiles.
- * 
- * The 'quadIndex' variable is a 4x4 array that represents the tiles. The center 
- * four (index numbers: 5, 6, 9, 10) are what is visible. Each quadIndex value is an
- * offset vector. The vector contains whole numbers and represents how many tiles in offset
- * this location is from the center of the map. So for example the index 11 [Vector3f(2, 0, 1)]
- * is located 2*terrainSize in X axis and 1*terrainSize in Z axis.
- * 
- * As the camera moves, it tests what cameraCell it is in. Each camera cell covers four quad tiles
- * and is half way inside each one.
- * 
- * +-------+-------+
- * | 1     |     4 |    Four terrainQuads that make up the grid
- * |    *..|..*    |    with the cameraCell in the middle, covering
+import java.util.logging.Logger;
+
+/**
+ * <p>
+ * TerrainGrid itself is an actual TerrainQuad. Its four children are the visible four tiles.</p>
+ * </p><p>
+ * The grid is indexed by cells. Each cell has an integer XZ coordinate originating at 0,0.
+ * TerrainGrid will piggyback on the TerrainLodControl so it can use the camera for its
+ * updates as well. It does this in the overwritten update() method.
+ * </p><p>
+ * It uses an LRU (Least Recently Used) cache of 16 terrain tiles (full TerrainQuadTrees). The
+ * center 4 are the ones that are visible. As the camera moves, it checks what camera cell it is in
+ * and will attach the now visible tiles.
+ * </p><p>
+ * The 'quadIndex' variable is a 4x4 array that represents the tiles. The center
+ * four (index numbers: 5, 6, 9, 10) are what is visible. Each quadIndex value is an
+ * offset vector. The vector contains whole numbers and represents how many tiles in offset
+ * this location is from the center of the map. So for example the index 11 [Vector3f(2, 0, 1)]
+ * is located 2*terrainSize in X axis and 1*terrainSize in Z axis.
+ * </p><p>
+ * As the camera moves, it tests what cameraCell it is in. Each camera cell covers four quad tiles
+ * and is half way inside each one.
+ * </p><pre>
+ * +-------+-------+
+ * | 1     |     4 |    Four terrainQuads that make up the grid
+ * |    *..|..*    |    with the cameraCell in the middle, covering
  * |----|--|--|----|    all four quads.
- * |    *..|..*    |
- * | 2     |     3 |
- * +-------+-------+
- * 
- * This results in the effect of when the camera gets half way across one of the sides of a quad to
- * an empty (non-loaded) area, it will trigger the system to load in the next tiles.
- * 
- * The tile loading is done on a background thread, and once the tile is loaded, then it is
- * attached to the qrid quad tree, back on the OGL thread. It will grab the terrain quad from
- * the LRU cache if it exists. If it does not exist, it will load in the new TerrainQuad tile.
- * 
- * The loading of new tiles triggers events for any TerrainGridListeners. The events are:
- *  -tile Attached
- *  -tile Detached
- *  -grid moved.
- * 
- * These allow physics to update, and other operation (often needed for loading the terrain) to occur
- * at the right time.
- * 
- * @author Anthyon
- */
-public class TerrainGrid extends TerrainQuad {
+ * |    *..|..*    |
+ * | 2     |     3 |
+ * +-------+-------+
+ * </pre><p>
+ * This results in the effect of when the camera gets half way across one of the sides of a quad to
+ * an empty (non-loaded) area, it will trigger the system to load in the next tiles.
+ * </p><p>
+ * The tile loading is done on a background thread, and once the tile is loaded, then it is
+ * attached to the qrid quad tree, back on the OGL thread. It will grab the terrain quad from
+ * the LRU cache if it exists. If it does not exist, it will load in the new TerrainQuad tile.
+ * </p><p>
+ * The loading of new tiles triggers events for any TerrainGridListeners. The events are:
+ * <ul>
+ *  <li>tile Attached
+ *  <li>tile Detached
+ *  <li>grid moved.
+ * </ul>
+ * <p>
+ * These allow physics to update, and other operation (often needed for loading the terrain) to occur
+ * at the right time.
+ * </p>
+ * @author Anthyon
+ */
 
     protected static final Logger log = Logger.getLogger(TerrainGrid.class.getCanonicalName());
     protected Vector3f currentCamCell = Vector3f.ZERO;