3D系列4.15 圆柱形Billboarding
你可以在3.11 Billboarding:在3D世界绘制2D图像使它们总是面向相机中看到Billboarding的详细解释,那个教程介绍了球形billboarding和圆柱形billboarding ,可以在CPU上计算,也可以在GPU上计算。所以,本章只简短讨论一下理论,重点放在代码的实现上。
创建了多纹理地形和水面后,现在需要在地形上放置一些树木。
我们可以通过加载一个3D模型,在地形上绘制几百次。问题是这样做帧频会大大下降甚至低于1帧/秒。
这个问题可以通过使用billboarding加以解决,billboarding是一个使用地非常广泛并十分重要的技术。Billboarding使用一个简单的2D图像代替3D模型,在树木的例子中,我们使用一张树的2D图像代替树的3D模型,它的位置与在3D世界中的位置相同。剩下的唯一一件事就是确保图像总是面朝相机,下图解释了为什么:
左图显示了3D世界中不同位置的5张图像,右图显示了同样的5张图像,但是面朝相机。可以想象如果图像包含树木的话,右图才是我们需要的结果。你使用两个三角形,六个顶点绘制billboard。对每个billboard,六个顶点需要包含正确的纹理坐标,但只需包含相同的位置:billboard的底边中点的位置,如下图所示。这很容易指定,因为这个位置就是树干与地形的交点。
下面我们会创建一个包含位置数据的集合。这个方法以这个集合为参数,集合中的每个位置都会生成6个顶点,代码来自于3.11 Billboarding:在3D世界绘制2D图像使它们总是面向相机:
private void CreateBillboardVerticesFromList(List<Vector3> treeList) { VertexPositionTexture[] billboardVertices = new VertexPositionTexture[treeList.Count * 6]; int i = 0; foreach (Vector3 currentV3 in treeList) { billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(0, 0)); billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(1, 0)); billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(1, 1)); billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(0, 0)); billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(1, 1)); billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(0, 1)); } treeVertexBuffer = new VertexBuffer(device, billboardVertices.Length * VertexPositionTexture.SizeInBytes, BufferUsage.WriteOnly); treeVertexBuffer.SetData(billboardVertices); treeVertexDeclaration = new VertexDeclaration(device, VertexPositionTexture.VertexElements); }
顶点数组存储在VertexBuffer中, 我们需要在代码顶部将它作为变量: VertexBuffer treeVertexBuffer; VertexDeclaration treeVertexDeclaration; 这些顶点通过顶点着色器转换到正确的位置,这样billboards会始终面朝相机。计算的HLSL代码来自于3.11 Billboarding:在3D世界绘制2D图像使它们总是面向相机。那个教程中的位置指定为billboard 的中央,而本例中我们指定为底边中点,所以我改变了顶点着色器中这行代码:
finalPosition += (1.5f-inTexCoord.y*1.5f)*upVector;
确保加载bbEffect.fx文件并添加以下变量:
Effect bbEffect;
并在LoadContent方法中加载:
bbEffect = Content.Load<Effect> ("bbEffect");
创建一个简单的方法生成一个集合,这个集合包含一些树的位置信息:
private List<Vector3> GenerateTreePositions(VertexMultitextured[] terrainVertices) { List<Vector3> treeList = new List<Vector3> (); treeList.Add(terrainVertices[3310].Position); treeList.Add(terrainVertices[3315].Position); treeList.Add(terrainVertices[3320].Position); treeList.Add(terrainVertices[3325].Position); return treeList; }
这个方法创建了一个集合,包含我在地形上随机取的4个位置。下一章我们会扩展这个方法,现在将绘制4棵树。确保在LoadVertices方法中调用这两个方法:
List<Vector3> treeList = GenerateTreePositions(terrainVertices); CreateBillboardVerticesFromList(treeList);
我们还需要导入一张树的2D图像并添加以下变量:
Texture2D treeTexture;
在LoadTextures方法中加载:
treeTexture = Content.Load<Texture2D> ("tree");
有了effect,纹理和顶点,就做好了绘制三角形的准备。下面是绘制代码:
private void DrawBillboards(Matrix currentViewMatrix) { bbEffect.CurrentTechnique = bbEffect.Techniques["CylBillboard"]; bbEffect.Parameters["xWorld"].SetValue(Matrix.Identity); bbEffect.Parameters["xView"].SetValue(currentViewMatrix); bbEffect.Parameters["xProjection"].SetValue(projectionMatrix); bbEffect.Parameters["xCamPos"].SetValue(cameraPosition); bbEffect.Parameters["xAllowedRotDir"].SetValue(new Vector3(0, 1, 0)); bbEffect.Parameters["xBillboardTexture"].SetValue(treeTexture); bbEffect.Begin(); foreach (EffectPass pass in bbEffect.CurrentTechnique.Passes) { pass.Begin(); device.Vertices[0].SetSource(treeVertexBuffer, 0, VertexPositionTexture.SizeInBytes); device.VertexDeclaration = treeVertexDeclaration; int noVertices = treeVertexBuffer.SizeInBytes / VertexPositionTexture.SizeInBytes; int noTriangles = noVertices / 3; device.DrawPrimitives(PrimitiveType.TriangleList, 0, noTriangles); pass.End(); } bbEffect.End(); }
我们选择.fx文件中的圆柱形billboarding technique并设置必需的XNA-to-HLSL变量。最重要的是xAllowedRotDir变量,它指定了2D图像绕着哪根轴旋转。球形和圆柱形billboarding的不同在于:在球形billboarding中,2D图像,2D图像可以绕着所有轴旋转。而本例中我们处理的数,我们想让树绕着树干旋转,即(0,1,0) Up轴旋转。
现在在Draw method方法的最后调用这个方法:
DrawBillboards(viewMatrix);
现在运行代码,你可以看到4棵树!试着将相机在树周围移动,它们总是朝向相机的。但是你还可以看到矩形的图像,这是因为树周围的黑色边界。幸运的是,我们的树纹理包含透明信息,所以在DrawBillboards方法中使用以下代码开启alpha混合:
device.RenderState.AlphaBlendEnable = true; device.RenderState.SourceBlend = Blend.SourceAlpha; device.RenderState.DestinationBlend = Blend.InverseSourceAlpha;
这会开启常规的alpha混合。
finalColor=pixelShaderColor*pixelShaderAlpha+colorAlreadyPresent*(1-pixelshader)
别忘了在方法的最后关闭alpha混合,否则下一帧你的3D世界都会变得透明!
device.RenderState.AlphaBlendEnable = false;
运行代码截图如下:
本章展示了基本的billboarding。当你绘制上百个billboards就会显示它的威力,我们会在下一章中实现一些树林。
本章的XNA代码如下,红色代码为相对于上一章改变的部分:
using System;
using System.Collections.Generic;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Net;
using Microsoft.Xna.Framework.Storage;
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namespace XNAseries4
{
public struct VertexMultitextured
{
public Vector3 Position;
public Vector3 Normal;
public Vector4 TextureCoordinate;
public Vector4 TexWeights;
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public static int SizeInBytes = (3 + 3 + 4 + 4) * sizeof(float);
public static VertexElement[] VertexElements = new VertexElement[]
{
new VertexElement( 0, 0, VertexElementFormat.Vector3, VertexElementMethod.Default, VertexElementUsage.Position, 0 ),
new VertexElement( 0, sizeof(float) * 3, VertexElementFormat.Vector3, VertexElementMethod.Default, VertexElementUsage.Normal, 0 ),
new VertexElement( 0, sizeof(float) * 6, VertexElementFormat.Vector4, VertexElementMethod.Default, VertexElementUsage.TextureCoordinate, 0 ),
new VertexElement( 0, sizeof(float) * 10, VertexElementFormat.Vector4, VertexElementMethod.Default, VertexElementUsage.TextureCoordinate, 1 ),
};
}
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public class Game1 : Microsoft.Xna.Framework.Game
{
GraphicsDeviceManager graphics;
GraphicsDevice device;
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int terrainWidth;
int terrainLength;
float[,] heightData;
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VertexBuffer terrainVertexBuffer;
IndexBuffer terrainIndexBuffer;
VertexDeclaration terrainVertexDeclaration;
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VertexBuffer waterVertexBuffer;
VertexDeclaration waterVertexDeclaration;
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VertexBuffer treeVertexBuffer;
VertexDeclaration treeVertexDeclaration;
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Effect effect;
Effect bbEffect;
Matrix viewMatrix;
Matrix projectionMatrix;
Matrix reflectionViewMatrix;
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Vector3 cameraPosition = new Vector3(130, 30, -50);
float leftrightRot = MathHelper.PiOver2;
float updownRot = -MathHelper.Pi / 10.0f;
const float rotationSpeed = 0.3f;
const float moveSpeed = 30.0f;
MouseState originalMouseState;
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Texture2D grassTexture;
Texture2D sandTexture;
Texture2D rockTexture;
Texture2D snowTexture;
Texture2D cloudMap;
Texture2D waterBumpMap;
Texture2D treeTexture;
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Model skyDome;
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const float waterHeight = 5.0f;
RenderTarget2D refractionRenderTarget;
Texture2D refractionMap;
RenderTarget2D reflectionRenderTarget;
Texture2D reflectionMap;
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Vector3 windDirection = new Vector3(0, 0, 1);
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public Game1()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
}
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protected override void Initialize()
{
graphics.PreferredBackBufferWidth = 500;
graphics.PreferredBackBufferHeight = 500;
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graphics.ApplyChanges();
Window.Title = "Riemer's XNA Tutorials -- Series 4";
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base.Initialize();
}
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protected override void LoadContent()
{
device = GraphicsDevice;
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effect = Content.Load<Effect> ("Series4Effects");
bbEffect = Content.Load<Effect> ("bbEffect"); UpdateViewMatrix();
projectionMatrix = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, device.Viewport.AspectRatio, 0.3f, 1000.0f);
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Mouse.SetPosition(device.Viewport.Width / 2, device.Viewport.Height / 2);
originalMouseState = Mouse.GetState();
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skyDome = Content.Load<Model> ("dome"); skyDome.Meshes[0].MeshParts[0].Effect = effect.Clone(device);
PresentationParameters pp = device.PresentationParameters;
refractionRenderTarget = new RenderTarget2D(device, pp.BackBufferWidth, pp.BackBufferHeight, 1, device.DisplayMode.Format);
reflectionRenderTarget = new RenderTarget2D(device, pp.BackBufferWidth, pp.BackBufferHeight, 1, device.DisplayMode.Format);
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LoadVertices();
LoadTextures();
}
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private void LoadVertices()
{
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Texture2D heightMap = Content.Load<Texture2D> ("heightmap"); LoadHeightData(heightMap);
VertexMultitextured[] terrainVertices = SetUpTerrainVertices();
int[] terrainIndices = SetUpTerrainIndices();
terrainVertices = CalculateNormals(terrainVertices, terrainIndices);
CopyToTerrainBuffers(terrainVertices, terrainIndices);
terrainVertexDeclaration = new VertexDeclaration(device, VertexMultitextured.VertexElements);
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SetUpWaterVertices();
waterVertexDeclaration = new VertexDeclaration(device, VertexPositionTexture.VertexElements);
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List<Vector3> treeList = GenerateTreePositions(terrainVertices); CreateBillboardVerticesFromList(treeList);
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}
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private void LoadTextures()
{
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grassTexture = Content.Load<Texture2D> ("grass");
sandTexture = Content.Load<Texture2D> ("sand");
rockTexture = Content.Load<Texture2D> ("rock");
snowTexture = Content.Load<Texture2D> ("snow");
cloudMap = Content.Load<Texture2D> ("cloudMap");
waterBumpMap = Content.Load<Texture2D> ("waterbump");
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treeTexture = Content.Load<Texture2D> ("tree");
}
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private void LoadHeightData(Texture2D heightMap)
{
float minimumHeight = float.MaxValue;
float maximumHeight = float.MinValue;
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terrainWidth = heightMap.Width;
terrainLength = heightMap.Height;
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Color[] heightMapColors = new Color[terrainWidth * terrainLength];
heightMap.GetData(heightMapColors);
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heightData = new float[terrainWidth, terrainLength];
for (int x = 0; x < terrainWidth; x++)
for (int y = 0; y < terrainLength; y++)
{
heightData[x, y] = heightMapColors[x + y * terrainWidth].R;
if (heightData[x, y] < minimumHeight) minimumHeight = heightData[x, y];
if (heightData[x, y] > maximumHeight) maximumHeight = heightData[x, y];
}
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for (int x = 0; x < terrainWidth; x++)
for (int y = 0; y < terrainLength; y++)
heightData[x, y] = (heightData[x, y] - minimumHeight) / (maximumHeight - minimumHeight) * 30.0f;
}
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private VertexMultitextured[] SetUpTerrainVertices()
{
VertexMultitextured[] terrainVertices = new VertexMultitextured[terrainWidth * terrainLength];
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for (int x = 0; x < terrainWidth; x++)
{
for (int y = 0; y < terrainLength; y++)
{
terrainVertices[x + y * terrainWidth].Position = new Vector3(x, heightData[x, y], -y);
terrainVertices[x + y * terrainWidth].TextureCoordinate.X = (float)x / 30.0f;
terrainVertices[x + y * terrainWidth].TextureCoordinate.Y = (float)y / 30.0f;
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terrainVertices[x + y * terrainWidth].TexWeights.X = MathHelper.Clamp(1.0f - Math.Abs(heightData[x, y] - 0) / 8.0f, 0, 1);
terrainVertices[x + y * terrainWidth].TexWeights.Y = MathHelper.Clamp(1.0f - Math.Abs(heightData[x, y] - 12) / 6.0f, 0, 1);
terrainVertices[x + y * terrainWidth].TexWeights.Z = MathHelper.Clamp(1.0f - Math.Abs(heightData[x, y] - 20) / 6.0f, 0, 1);
terrainVertices[x + y * terrainWidth].TexWeights.W = MathHelper.Clamp(1.0f - Math.Abs(heightData[x, y] - 30) / 6.0f, 0, 1);
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float total = terrainVertices[x + y * terrainWidth].TexWeights.X;
total += terrainVertices[x + y * terrainWidth].TexWeights.Y;
total += terrainVertices[x + y * terrainWidth].TexWeights.Z;
total += terrainVertices[x + y * terrainWidth].TexWeights.W;
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terrainVertices[x + y * terrainWidth].TexWeights.X /= total;
terrainVertices[x + y * terrainWidth].TexWeights.Y /= total;
terrainVertices[x + y * terrainWidth].TexWeights.Z /= total;
terrainVertices[x + y * terrainWidth].TexWeights.W /= total;
}
}
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return terrainVertices;
}
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private int[] SetUpTerrainIndices()
{
int[] indices = new int[(terrainWidth - 1) * (terrainLength - 1) * 6];
int counter = 0;
for (int y = 0; y < terrainLength - 1; y++)
{
for (int x = 0; x < terrainWidth - 1; x++)
{
int lowerLeft = x + y * terrainWidth;
int lowerRight = (x + 1) + y * terrainWidth;
int topLeft = x + (y + 1) * terrainWidth;
int topRight = (x + 1) + (y + 1) * terrainWidth;
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indices[counter++] = topLeft;
indices[counter++] = lowerRight;
indices[counter++] = lowerLeft;
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indices[counter++] = topLeft;
indices[counter++] = topRight;
indices[counter++] = lowerRight;
}
}
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return indices;
}
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private VertexMultitextured[] CalculateNormals(VertexMultitextured[] vertices, int[] indices)
{
for (int i = 0; i < vertices.Length; i++)
vertices[i].Normal = new Vector3(0, 0, 0);
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for (int i = 0; i < indices.Length / 3; i++)
{
int index1 = indices[i * 3];
int index2 = indices[i * 3 + 1];
int index3 = indices[i * 3 + 2];
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Vector3 side1 = vertices[index1].Position - vertices[index3].Position;
Vector3 side2 = vertices[index1].Position - vertices[index2].Position;
Vector3 normal = Vector3.Cross(side1, side2);
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vertices[index1].Normal += normal;
vertices[index2].Normal += normal;
vertices[index3].Normal += normal;
}
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for (int i = 0; i < vertices.Length; i++)
vertices[i].Normal.Normalize();
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return vertices;
}
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private void CopyToTerrainBuffers(VertexMultitextured[] vertices, int[] indices)
{
terrainVertexBuffer = new VertexBuffer(device, vertices.Length * VertexMultitextured.SizeInBytes, BufferUsage.WriteOnly);
terrainVertexBuffer.SetData(vertices);
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terrainIndexBuffer = new IndexBuffer(device, typeof(int), indices.Length, BufferUsage.WriteOnly);
terrainIndexBuffer.SetData(indices);
}
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private void SetUpWaterVertices()
{
VertexPositionTexture[] waterVertices = new VertexPositionTexture[6];
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waterVertices[0] = new VertexPositionTexture(new Vector3(0, waterHeight, 0), new Vector2(0, 1));
waterVertices[2] = new VertexPositionTexture(new Vector3(terrainWidth, waterHeight, -terrainLength), new Vector2(1, 0));
waterVertices[1] = new VertexPositionTexture(new Vector3(0, waterHeight, -terrainLength), new Vector2(0, 0));
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waterVertices[3] = new VertexPositionTexture(new Vector3(0, waterHeight, 0), new Vector2(0, 1));
waterVertices[5] = new VertexPositionTexture(new Vector3(terrainWidth, waterHeight, 0), new Vector2(1, 1));
waterVertices[4] = new VertexPositionTexture(new Vector3(terrainWidth, waterHeight, -terrainLength), new Vector2(1, 0));
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waterVertexBuffer = new VertexBuffer(device, waterVertices.Length * VertexPositionTexture.SizeInBytes, BufferUsage.WriteOnly);
waterVertexBuffer.SetData(waterVertices);
}
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private void CreateBillboardVerticesFromList(List<Vector3> treeList) {
VertexPositionTexture[] billboardVertices = new VertexPositionTexture[treeList.Count * 6];
int i = 0;
foreach (Vector3 currentV3 in treeList)
{
billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(0, 0));
billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(1, 0));
billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(1, 1));
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billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(0, 0));
billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(1, 1));
billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(0, 1));
}
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treeVertexBuffer = new VertexBuffer(device, billboardVertices.Length * VertexPositionTexture.SizeInBytes, BufferUsage.WriteOnly);
treeVertexBuffer.SetData(billboardVertices);
treeVertexDeclaration = new VertexDeclaration(device, VertexPositionTexture.VertexElements);
}
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private List<Vector3> GenerateTreePositions(VertexMultitextured[] terrainVertices) {
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List<Vector3> treeList = new List<Vector3> ();
treeList.Add(terrainVertices[3310].Position);
treeList.Add(terrainVertices[3315].Position);
treeList.Add(terrainVertices[3320].Position);
treeList.Add(terrainVertices[3325].Position);
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return treeList;
}
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protected override void UnloadContent()
{
}
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protected override void Update(GameTime gameTime)
{
if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
this.Exit();
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float timeDifference = (float)gameTime.ElapsedGameTime.TotalMilliseconds / 1000.0f;
ProcessInput(timeDifference);
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base.Update(gameTime);
}
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private void ProcessInput(float amount)
{
MouseState currentMouseState = Mouse.GetState();
if (currentMouseState != originalMouseState)
{
float xDifference = currentMouseState.X - originalMouseState.X;
float yDifference = currentMouseState.Y - originalMouseState.Y;
leftrightRot -= rotationSpeed * xDifference * amount;
updownRot -= rotationSpeed * yDifference * amount;
Mouse.SetPosition(device.Viewport.Width / 2, device.Viewport.Height / 2);
UpdateViewMatrix();
}
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Vector3 moveVector = new Vector3(0, 0, 0);
KeyboardState keyState = Keyboard.GetState();
if (keyState.IsKeyDown(Keys.Up) || keyState.IsKeyDown(Keys.W))
moveVector += new Vector3(0, 0, -1);
if (keyState.IsKeyDown(Keys.Down) || keyState.IsKeyDown(Keys.S))
moveVector += new Vector3(0, 0, 1);
if (keyState.IsKeyDown(Keys.Right) || keyState.IsKeyDown(Keys.D))
moveVector += new Vector3(1, 0, 0);
if (keyState.IsKeyDown(Keys.Left) || keyState.IsKeyDown(Keys.A))
moveVector += new Vector3(-1, 0, 0);
if (keyState.IsKeyDown(Keys.Q))
moveVector += new Vector3(0, 1, 0);
if (keyState.IsKeyDown(Keys.Z))
moveVector += new Vector3(0, -1, 0);
AddToCameraPosition(moveVector * amount);
}
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private void AddToCameraPosition(Vector3 vectorToAdd)
{
Matrix cameraRotation = Matrix.CreateRotationX(updownRot) * Matrix.CreateRotationY(leftrightRot);
Vector3 rotatedVector = Vector3.Transform(vectorToAdd, cameraRotation);
cameraPosition += moveSpeed * rotatedVector;
UpdateViewMatrix();
}
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private void UpdateViewMatrix()
{
Matrix cameraRotation = Matrix.CreateRotationX(updownRot) * Matrix.CreateRotationY(leftrightRot);
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Vector3 cameraOriginalTarget = new Vector3(0, 0, -1);
Vector3 cameraOriginalUpVector = new Vector3(0, 1, 0);
Vector3 cameraRotatedTarget = Vector3.Transform(cameraOriginalTarget, cameraRotation);
Vector3 cameraFinalTarget = cameraPosition + cameraRotatedTarget;
Vector3 cameraRotatedUpVector = Vector3.Transform(cameraOriginalUpVector, cameraRotation);
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viewMatrix = Matrix.CreateLookAt(cameraPosition, cameraFinalTarget, cameraRotatedUpVector);
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Vector3 reflCameraPosition = cameraPosition;
reflCameraPosition.Y = -cameraPosition.Y + waterHeight * 2;
Vector3 reflTargetPos = cameraFinalTarget;
reflTargetPos.Y = -cameraFinalTarget.Y + waterHeight * 2;
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Vector3 cameraRight = Vector3.Transform(new Vector3(1, 0, 0), cameraRotation);
Vector3 invUpVector = Vector3.Cross(cameraRight, reflTargetPos - reflCameraPosition);
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reflectionViewMatrix = Matrix.CreateLookAt(reflCameraPosition, reflTargetPos, invUpVector);
}
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protected override void Draw(GameTime gameTime)
{
float time = (float)gameTime.TotalGameTime.TotalMilliseconds / 100.0f;
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DrawRefractionMap();
DrawReflectionMap();
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device.Clear(ClearOptions.Target | ClearOptions.DepthBuffer, Color.White, 1.0f, 0);
DrawSkyDome(viewMatrix);
DrawTerrain(viewMatrix);
DrawWater(time);
DrawBillboards(viewMatrix);
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base.Draw(gameTime);
}
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private void DrawTerrain(Matrix currentViewMatrix)
{
effect.CurrentTechnique = effect.Techniques["MultiTextured"];
effect.Parameters["xTexture0"].SetValue(sandTexture);
effect.Parameters["xTexture1"].SetValue(grassTexture);
effect.Parameters["xTexture2"].SetValue(rockTexture);
effect.Parameters["xTexture3"].SetValue(snowTexture);
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Matrix worldMatrix = Matrix.Identity;
effect.Parameters["xWorld"].SetValue(worldMatrix);
effect.Parameters["xView"].SetValue(currentViewMatrix);
effect.Parameters["xProjection"].SetValue(projectionMatrix);
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effect.Parameters["xEnableLighting"].SetValue(true);
effect.Parameters["xAmbient"].SetValue(0.4f);
effect.Parameters["xLightDirection"].SetValue(new Vector3(-0.5f, -1, -0.5f));
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effect.Begin();
foreach (EffectPass pass in effect.CurrentTechnique.Passes)
{
pass.Begin();
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device.Vertices[0].SetSource(terrainVertexBuffer, 0, VertexMultitextured.SizeInBytes);
device.Indices = terrainIndexBuffer;
device.VertexDeclaration = terrainVertexDeclaration;
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int noVertices = terrainVertexBuffer.SizeInBytes / VertexMultitextured.SizeInBytes;
int noTriangles = terrainIndexBuffer.SizeInBytes / sizeof(int) / 3;
device.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, noVertices, 0, noTriangles);
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pass.End();
}
effect.End();
}
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private void DrawSkyDome(Matrix currentViewMatrix)
{
device.RenderState.DepthBufferWriteEnable = false;
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Matrix[] modelTransforms = new Matrix[skyDome.Bones.Count];
skyDome.CopyAbsoluteBoneTransformsTo(modelTransforms);
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Matrix wMatrix = Matrix.CreateTranslation(0, -0.3f, 0) * Matrix.CreateScale(100) * Matrix.CreateTranslation(cameraPosition);
foreach (ModelMesh mesh in skyDome.Meshes)
{
foreach (Effect currentEffect in mesh.Effects)
{
Matrix worldMatrix = modelTransforms[mesh.ParentBone.Index] * wMatrix;
currentEffect.CurrentTechnique = currentEffect.Techniques["Textured"];
currentEffect.Parameters["xWorld"].SetValue(worldMatrix);
currentEffect.Parameters["xView"].SetValue(currentViewMatrix);
currentEffect.Parameters["xProjection"].SetValue(projectionMatrix);
currentEffect.Parameters["xTexture"].SetValue(cloudMap);
currentEffect.Parameters["xEnableLighting"].SetValue(false);
}
mesh.Draw();
}
device.RenderState.DepthBufferWriteEnable = true;
}
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private Plane CreatePlane(float height, Vector3 planeNormalDirection, Matrix currentViewMatrix, bool clipSide)
{
planeNormalDirection.Normalize();
Vector4 planeCoeffs = new Vector4(planeNormalDirection, height);
if (clipSide)
planeCoeffs *= -1;
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Matrix worldViewProjection = currentViewMatrix * projectionMatrix;
Matrix inverseWorldViewProjection = Matrix.Invert(worldViewProjection);
inverseWorldViewProjection = Matrix.Transpose(inverseWorldViewProjection);
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planeCoeffs = Vector4.Transform(planeCoeffs, inverseWorldViewProjection);
Plane finalPlane = new Plane(planeCoeffs);
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return finalPlane;
}
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private void DrawRefractionMap()
{
Plane refractionPlane = CreatePlane(waterHeight + 1.5f, new Vector3(0, -1, 0), viewMatrix, false);
device.ClipPlanes[0].Plane = refractionPlane;
device.ClipPlanes[0].IsEnabled = true;
device.SetRenderTarget(0, refractionRenderTarget);
device.Clear(ClearOptions.Target | ClearOptions.DepthBuffer, Color.Black, 1.0f, 0);
DrawTerrain(viewMatrix);
device.ClipPlanes[0].IsEnabled = false;
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device.SetRenderTarget(0, null);
refractionMap = refractionRenderTarget.GetTexture();
}
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private void DrawReflectionMap()
{
Plane reflectionPlane = CreatePlane(waterHeight - 0.5f, new Vector3(0, -1, 0), reflectionViewMatrix, true);
device.ClipPlanes[0].Plane = reflectionPlane;
device.ClipPlanes[0].IsEnabled = true;
device.SetRenderTarget(0, reflectionRenderTarget);
device.Clear(ClearOptions.Target | ClearOptions.DepthBuffer, Color.Black, 1.0f, 0);
DrawTerrain(reflectionViewMatrix);
DrawSkyDome(reflectionViewMatrix);
device.ClipPlanes[0].IsEnabled = false;
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device.SetRenderTarget(0, null);
reflectionMap = reflectionRenderTarget.GetTexture();
}
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private void DrawWater(float time)
{
effect.CurrentTechnique = effect.Techniques["Water"];
Matrix worldMatrix = Matrix.Identity;
effect.Parameters["xWorld"].SetValue(worldMatrix);
effect.Parameters["xView"].SetValue(viewMatrix);
effect.Parameters["xReflectionView"].SetValue(reflectionViewMatrix);
effect.Parameters["xProjection"].SetValue(projectionMatrix);
effect.Parameters["xReflectionMap"].SetValue(reflectionMap);
effect.Parameters["xRefractionMap"].SetValue(refractionMap);
effect.Parameters["xWaterBumpMap"].SetValue(waterBumpMap);
effect.Parameters["xWaveLength"].SetValue(0.1f);
effect.Parameters["xWaveHeight"].SetValue(0.3f);
effect.Parameters["xCamPos"].SetValue(cameraPosition);
effect.Parameters["xTime"].SetValue(time);
effect.Parameters["xWindForce"].SetValue(0.002f);
effect.Parameters["xWindDirection"].SetValue(windDirection);
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effect.Begin();
foreach (EffectPass pass in effect.CurrentTechnique.Passes)
{
pass.Begin();
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device.Vertices[0].SetSource(waterVertexBuffer, 0, VertexPositionTexture.SizeInBytes);
device.VertexDeclaration = waterVertexDeclaration;
int noVertices = waterVertexBuffer.SizeInBytes / VertexPositionTexture.SizeInBytes;
device.DrawPrimitives(PrimitiveType.TriangleList, 0, noVertices / 3);
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pass.End();
}
effect.End();
}
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private void DrawBillboards(Matrix currentViewMatrix)
{
bbEffect.CurrentTechnique = bbEffect.Techniques["CylBillboard"];
bbEffect.Parameters["xWorld"].SetValue(Matrix.Identity);
bbEffect.Parameters["xView"].SetValue(currentViewMatrix);
bbEffect.Parameters["xProjection"].SetValue(projectionMatrix);
bbEffect.Parameters["xCamPos"].SetValue(cameraPosition);
bbEffect.Parameters["xAllowedRotDir"].SetValue(new Vector3(0, 1, 0));
bbEffect.Parameters["xBillboardTexture"].SetValue(treeTexture);
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device.RenderState.AlphaBlendEnable = true;
device.RenderState.SourceBlend = Blend.SourceAlpha;
device.RenderState.DestinationBlend = Blend.InverseSourceAlpha;
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bbEffect.Begin();
foreach (EffectPass pass in bbEffect.CurrentTechnique.Passes)
{
pass.Begin();
device.Vertices[0].SetSource(treeVertexBuffer, 0, VertexPositionTexture.SizeInBytes);
device.VertexDeclaration = treeVertexDeclaration;
int noVertices = treeVertexBuffer.SizeInBytes / VertexPositionTexture.SizeInBytes;
int noTriangles = noVertices / 3;
device.DrawPrimitives(PrimitiveType.TriangleList, 0, noTriangles);
pass.End();
}
bbEffect.End();
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device.RenderState.AlphaBlendEnable = false;
}
}
}
bbEffect.fx文件的代码如下:
//------- XNA interface --------
float4x4 xView;
float4x4 xProjection;
float4x4 xWorld;
float3 xCamPos;
float3 xAllowedRotDir;
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//------- Texture Samplers --------
Texture xBillboardTexture;
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sampler textureSampler = sampler_state { texture = <xBillboardTexture> ; magfilter = LINEAR; minfilter = LINEAR; mipfilter=LINEAR; AddressU = CLAMP; AddressV = CLAMP;};
struct BBVertexToPixel
{
float4 Position : POSITION;
float2 TexCoord : TEXCOORD0;
};
struct BBPixelToFrame
{
float4 Color : COLOR0;
};
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//------- Technique: CylBillboard --------
BBVertexToPixel CylBillboardVS(float3 inPos: POSITION0, float2 inTexCoord: TEXCOORD0)
{
BBVertexToPixel Output = (BBVertexToPixel)0;
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float3 center = mul(inPos, xWorld);
float3 eyeVector = center - xCamPos;
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float3 upVector = xAllowedRotDir;
upVector = normalize(upVector);
float3 sideVector = cross(eyeVector,upVector);
sideVector = normalize(sideVector);
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float3 finalPosition = center;
finalPosition += (inTexCoord.x-0.5f)*sideVector;
finalPosition += (1.5f-inTexCoord.y*1.5f)*upVector;
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float4 finalPosition4 = float4(finalPosition, 1);
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float4x4 preViewProjection = mul (xView, xProjection);
Output.Position = mul(finalPosition4, preViewProjection);
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Output.TexCoord = inTexCoord;
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return Output;
}
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BBPixelToFrame BillboardPS(BBVertexToPixel PSIn) : COLOR0
{
BBPixelToFrame Output = (BBPixelToFrame)0;
Output.Color = tex2D(textureSampler, PSIn.TexCoord);
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return Output;
}
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technique CylBillboard
{
pass Pass0
{
VertexShader = compile vs_1_1 CylBillboardVS();
PixelShader = compile ps_1_1 BillboardPS();
}
}
发布时间:2009/12/29 上午9:15:11 阅读次数:11170