XNA Primitives画线 2(3D空间)
在XNA Primitives画线 1(2D和微量反射)的Demo中有很多的问题,比如,画的点不够精确、要画的线太多的话也就需要更多的点,这样的话对机子的性能可能要求就有点过了。
其实做现在这个Demo的主要目标也就是为了提高精度,在3D环境中我们可以用一个像素表示一个点,因此精确度应该就高的多。在XNA中 PrimitiveType.LineList可以直接画线,也可以由画出的线组成我们要的圆等图形。
另外,我想要实现全3D效果的话,我要用这种方式才行。
因为GraphicsDevice可以绘制点、线和三角形,我们的需要就主要是画线。如,根据四个点的坐标就可以绘制一个坐标轴,下面就是绘制坐标轴的方法:
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private void DrawCoordinate()
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{
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DrawLine(new Vector3(0 - Window.ClientBounds.Width / 2, 0, 0), new Vector3(Window.ClientBounds.Width / 2, 0, 0));
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DrawLine(new Vector3( 0,0 - Window.ClientBounds.Width / 2, 0), new Vector3( 0,Window.ClientBounds.Width / 2, 0));
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}
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现在让我们来绘制圆,XNA Primitives画线 1中的圆是由一个个的点组成的所以看起来就比较粗糙。这里的圆是由一个一个的线段,所以我就写了一个画线的方法:
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private void DrawLine(Vector3 point1, Vector3 point2)
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{
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VertexPositionColor[] vpcs = new VertexPositionColor[2];
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vpcs[0] = new VertexPositionColor(point1, Color.White);
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vpcs[1] = new VertexPositionColor(point2, Color.White);
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vertexDecl = new VertexDeclaration(GraphicsDevice, VertexPositionColor.VertexElements);
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GraphicsDevice.VertexDeclaration = vertexDecl;
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BasicEffect effect = new BasicEffect(GraphicsDevice, null);
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effect.View = view;
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effect.Projection = projection;
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effect.World = worldTrans;
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effect.Begin();
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foreach (EffectPass pass in effect.CurrentTechnique.Passes)
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{
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pass.Begin();
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GraphicsDevice.DrawUserPrimitives(PrimitiveType.LineList, vpcs, 0, 1);
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pass.End();
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}
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effect.End();
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}
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在开始画圆之前,我们还要为我们要画的圆创建好它的顶点:
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private Vector3[] CirlcePoint()
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{
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Vector3[] VertexPoints = new Vector3[120];
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Vector2 point = new Vector2(200,0);
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Matrix tranmatrix;
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for (int i = 0; i < 120;i++)
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{
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tranmatrix = new Matrix((float)Math.Cos(MathHelper.ToRadians( 3)), (float)Math.Sin(MathHelper.ToRadians( 3)), 0, 0,
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-1 * (float)Math.Sin(MathHelper.ToRadians( 3)), (float)Math.Cos(MathHelper.ToRadians( 3)), 0, 0,
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0, 0, 0, 0,
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0, 0, 0, 0
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);
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point = Vector2.Transform(point, tranmatrix);
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VertexPoints[i] = new Vector3(point.X, point.Y, 0);
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}
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return VertexPoints;
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}
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现在就开始画我们的圆了:
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看下效果
这个是比之前那个好的多吧。
剩下和就是主题部分了,其实原理我之前那个还是一样的。
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private void DrawMyEffect()
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{
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if (points[points.Length - 1].Length() >200)
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{
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ArrayList al = new ArrayList();
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foreach(Vector3 vec in points)
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{
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al.Add(vec);
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}
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al.Add(points[points.Length - 1]);
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points = (Vector3[])al.ToArray(typeof(Vector3));
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velocity = Vector3.Reflect(velocity, Vector3.Normalize(points[points.Length - 1]));
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}
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for( int i = 0; i < points.Length-1;i++)
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{
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DrawLine(points[i], points[i + 1]);
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}
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points[points.Length-1] += velocity;
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}
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效果如下:
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顺便贴出其它用到的方法:
随机的起点和方向
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private Vector3 GetRandomVector3()
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{
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Random rand=new Random(DateTime.Now.Second);
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return new Vector3((float)rand.Next(-180, 180), (float)rand.Next(-180, 180),0);
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}
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private Vector3 GetRandomVelocity()
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{
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Random rand = new Random();
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return new Vector3((float)rand.Next(-80, 80), (float)rand.Next(-80, 80), 0);
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}
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初始化
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protected override void Initialize()
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{
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IsMouseVisible = true;
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view = Matrix.CreateLookAt(new Vector3(0, 0, 800), Vector3.Zero, Vector3.Up);
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projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, 4 / 3f, 1, 10000);
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velocity = GetRandomVelocity();
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startPosition = GetRandomVector3();
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points = new Vector3[2];
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points[0] = startPosition;
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points[1] = startPosition + velocity;
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base.Initialize();
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}
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键盘控制
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private void HandelInput()
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{
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KeyboardState ks = Keyboard.GetState();
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if (ks.IsKeyDown(Keys.W))
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{
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worldTrans *= Matrix.CreateRotationX(MathHelper.ToRadians(10f));
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}
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if (ks.IsKeyDown(Keys.S))
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{
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worldTrans *= Matrix.CreateRotationX(MathHelper.ToRadians(-10f));
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}
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if (ks.IsKeyDown(Keys.A))
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{
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worldTrans *= Matrix.CreateRotationY(MathHelper.ToRadians(10f));
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}
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if (ks.IsKeyDown(Keys.D))
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{
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worldTrans *= Matrix.CreateRotationY(MathHelper.ToRadians(-10f));
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}
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if (ks.IsKeyDown(Keys.Q))
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{
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worldTrans *= Matrix.CreateRotationZ(MathHelper.ToRadians(10f));
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}
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if (ks.IsKeyDown(Keys.E))
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{
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worldTrans *= Matrix.CreateRotationZ(MathHelper.ToRadians(-10f));
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}
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if (ks.IsKeyDown(Keys.Up))
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{
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view *= Matrix.CreateTranslation(new Vector3(0,0,20));
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}
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if (ks.IsKeyDown(Keys.Down))
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{
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view *= Matrix.CreateTranslation(new Vector3(0, 0, -20));
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}
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}
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这里主要是在3D环境中画出的2D效果,本来想再将这个Demo做成3D效果的,可惜顶点没添加到好多的时候速度就已经很慢了,所以做成3D效果的话还不成形机子就死了,所以就免了。
现在更希望有高手能指教这里面的不足。