SE TTIN G UP DIFFER ENT CA MERA MODE S IN YOUR 3 D WORLD in Word

Generator ECC200 in Word SE TTIN G UP DIFFER ENT CA MERA MODE S IN YOUR 3 D WORLD

A quadtree is a simplified version of an octree. A quad needs to be divided only into four smaller quads, while an octree node needs to be divided into eight child cubes. An octree also needs to keep track of the position of all objects inside it, while a quadtree doesn t have to deal with this.

Create a new class, which will represent one quad, a node of your quadtree: namespace BookCode { class QTNode { private BoundingBox nodeBoundingBox; private private private private private private private private private private private private bool isEndNode; QTNode nodeUL; QTNode nodeUR; QTNode nodeLL; QTNode nodeLR; int width; int height; GraphicsDevice device; BasicEffect basicEffect; VertexBuffer nodeVertexBuffer; IndexBuffer nodeIndexBuffer; Texture2D grassTexture;

public static int NodesRendered; } } Let s discuss the variables each node will need to remember. The first one, the bounding box, is quite important. It is the smallest box, so all vertices of the current node are inside the box. Each frame, you will check whether the current box is in sight of the camera. The current node should forward the Draw call to its child nodes only if this is true. When creating a quadtree, you should specify the maximum size of the nodes. The isEndNode variable will store whether the current node is larger than this maximum size. If it is larger, the node should create four child nodes, stored in nodeUL to nodeLR, where UL stands for UpperLeft and LR stands for LowerRight. If the node has no child nodes, the node will actually have to draw some triangles when isEndNode is true. To do this, you will need to know its width and height. You ll also need a link to the graphics device and a working BasicEffect. Furthermore, you ll need a VertexBuffer and an IndexBuffer together with a Texture to render the triangles to the screen (see recipe 5-8). A node is created by calling its constructor method, like this one:

public QTNode(VertexPositionNormalTexture[,] vertexArray, GraphicsDevice device, Texture2D grassTexture, int maxSize) { this.device = device; this.grassTexture = grassTexture; basicEffect = new BasicEffect(device, null); width = vertexArray.GetLength(0); height = vertexArray.GetLength(1); nodeBoundingBox = CreateBoundingBox(vertexArray); isEndNode = width <= maxSize; isEndNode &= height <= maxSize; if (isEndNode) { VertexPositionNormalTexture[] vertices = Reshape2Dto1D<VertexPositionNormalTexture>(vertexArray); int[] indices = TerrainUtils.CreateTerrainIndices(width, height); TerrainUtils.CreateBuffers(vertices, indices, out nodeVertexBuffer, out nodeIndexBuffer, device); } else { CreateChildNodes(vertexArray, maxSize); } } A node needs a 2D array containing all of its vertices, together with a link to the device and texture, as well as the size after which the nodes should stop splitting themselves into child nodes. A link to the device and texture are immediately stored inside the node. The width and height of the current node are extracted from the 2D array containing the vertices. Given all vertices of this node, you calculate the bounding box using the CreateBoundingBox method that you ll define in a minute. Finally, you check whether the width and height of the current node are smaller than the maximum size. If this is the case, you create a valid VertexBuffer and IndexBuffer from the vertices of the current node. If the node is larger than the maximum size, you split the node into four child nodes.

Given the 2D array containing the vertices, you can easily store all their positions inside a list. The CreateFromPoints method of the BoundingBox class can generate a BoundingBox from this list of positions: private BoundingBox CreateBoundingBox(VertexPositionNormalTexture[,] vertexArray) {

List<Vector3> pointList = new List<Vector3>(); foreach (VertexPositionNormalTexture vertex in vertexArray) pointList.Add(vertex.Position); BoundingBox nodeBoundingBox = BoundingBox.CreateFromPoints(pointList); return nodeBoundingBox; }

You can use the CreateVertices and CreateIndices methods explained in recipe 5-8, which create a VertexBuffer and an IndexBuffer given a 1D array of vertices. This means you ll have to reshape your 2D array into a 1D array first, which you can do using this method: private { int int T[] T[] Reshape2Dto1D<T>(T[,] array2D) width = array2D.GetLength(0); height = array2D.GetLength(1); array1D = new T[width * height];

int i = 0; for (int z = 0; z < height; z++) for (int x = 0; x < width; x++) array1D[i++] = array2D[x, z]; return array1D; } This generic method accepts a 2D array of a type T (VertexPositionNormalTexture in your case), finds its size, and copies its contents into a 1D array.