| package com.jme3.terrain.geomipmap.lodcalc.util; |
| |
| import com.jme3.bounding.BoundingBox; |
| import com.jme3.collision.CollisionResults; |
| import com.jme3.math.Matrix4f; |
| import com.jme3.math.Ray; |
| import com.jme3.math.Vector3f; |
| import com.jme3.scene.Mesh; |
| import com.jme3.scene.VertexBuffer; |
| import com.jme3.scene.VertexBuffer.Type; |
| import com.jme3.util.BufferUtils; |
| import java.nio.FloatBuffer; |
| import java.nio.IntBuffer; |
| |
| /** |
| * Computes the entropy value δ (delta) for a given terrain block and |
| * LOD level. |
| * See the geomipmapping paper section |
| * "2.3.1 Choosing the appropriate GeoMipMap level" |
| * |
| * @author Kirill Vainer |
| */ |
| public class EntropyComputeUtil { |
| |
| public static float computeLodEntropy(Mesh terrainBlock, IntBuffer lodIndices){ |
| // Bounding box for the terrain block |
| BoundingBox bbox = (BoundingBox) terrainBlock.getBound(); |
| |
| // Vertex positions for the block |
| FloatBuffer positions = terrainBlock.getFloatBuffer(Type.Position); |
| |
| // Prepare to cast rays |
| Vector3f pos = new Vector3f(); |
| Vector3f dir = new Vector3f(0, -1, 0); |
| Ray ray = new Ray(pos, dir); |
| |
| // Prepare collision results |
| CollisionResults results = new CollisionResults(); |
| |
| // Set the LOD indices on the block |
| VertexBuffer originalIndices = terrainBlock.getBuffer(Type.Index); |
| |
| terrainBlock.clearBuffer(Type.Index); |
| terrainBlock.setBuffer(Type.Index, 3, lodIndices); |
| |
| // Recalculate collision mesh |
| terrainBlock.createCollisionData(); |
| |
| float entropy = 0; |
| for (int i = 0; i < positions.capacity() / 3; i++){ |
| BufferUtils.populateFromBuffer(pos, positions, i); |
| |
| float realHeight = pos.y; |
| |
| pos.addLocal(0, bbox.getYExtent(), 0); |
| ray.setOrigin(pos); |
| |
| results.clear(); |
| terrainBlock.collideWith(ray, Matrix4f.IDENTITY, bbox, results); |
| |
| if (results.size() > 0){ |
| Vector3f contactPoint = results.getClosestCollision().getContactPoint(); |
| float delta = Math.abs(realHeight - contactPoint.y); |
| entropy = Math.max(delta, entropy); |
| } |
| } |
| |
| // Restore original indices |
| terrainBlock.clearBuffer(Type.Index); |
| terrainBlock.setBuffer(originalIndices); |
| |
| return entropy; |
| } |
| |
| } |