From eac143830f0b2ee30f539c0d9f4135ccb2d50bd5 Mon Sep 17 00:00:00 2001
From: "bre..ns"
+ * 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 * |----|--|--|----| 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 | + * +-------+-------+ + *
+ * 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: + *
+ * These allow physics to update, and other operation (often needed for loading the terrain) to occur + * at the right time. + *
+ * @author Anthyon + */ protected static final Logger log = Logger.getLogger(TerrainGrid.class.getCanonicalName()); protected Vector3f currentCamCell = Vector3f.ZERO;