WPF可以提供的3D模型使我们可以轻松地创建3D实体，虽然目前来看还很有一些性能上的问题，不过对于一些简单的3D应用应该是可取的，毕竟其开发效率高，而且也容易上手。
下面给大家演示的是使用在WPF 3D上实现视角变换，通过鼠标拖动来变换观察视角，通过滚轮来放缩视距。
首先创建一个3D立方体，立方体是由六个面构成(F1, F2 ....F6)其XAML代码如下：
在Viewport中用六个面构成一个立方体， 每一个面都是一个GeometryModel3D。
下面就是如何来实现通过鼠标拖动来变换视角的功能。首先给Window对象添加几个有关的鼠标的事件：MouseMove、MouseLeftButtonDown和MouseWheel。
说明一下使用到的几个变量：
其中MouseLeftButtonDown是用来获取鼠标在进入拖动状态之前的位置，这样我们就可以根据鼠标位置的改变类变换视角。
Point mouseLastPosition;private void Viewport3D_MouseLeftButtonDown(object sender, MouseButtonEventArgs e){ mouseLastPosition = e.GetPosition(this);}
下面是MouseMove事件，实现视角的变换。首先鼠标在拖动的过程中，可能发生水平方向上的变化和垂直方向上的变化，所以，我们将对不同的变化方向进行不同的变换。这里我将水平变换和垂直变换已经分别封装至两个方法中：HorizontalTransform（水平变换）和VerticalTransform（垂直变换）
private void Viewport3D_MouseMove(object sender, MouseEventArgs e){ if (Mouse.LeftButton == MouseButtonState.Pressed) { Point newMousePosition = e.GetPosition(this); if (mouseLastPosition.X != newMousePosition.X) { HorizontalTransform(mouseLastPosition.X < newMousePosition.X, mouseDeltaFactor);//水平变换 } if (mouseLastPosition.Y != newMousePosition.Y)// change position in the horizontal direction { VerticalTransform(mouseLastPosition.Y > newMousePosition.Y, mouseDeltaFactor);//垂直变换 } mouseLastPosition = newMousePosition; }}
接下来我们就来看一下这两个变换方法的具体实现：
垂直变换：
private void VerticalTransform(bool upDown, double angleDeltaFactor) { Vector3D postion = new Vector3D(camera.Position.X, camera.Position.Y, camera.Position.Z); Vector3D rotateAxis = Vector3D.CrossProduct(postion, camera.UpDirection); RotateTransform3D rt3d = new RotateTransform3D(); AxisAngleRotation3D rotate = new AxisAngleRotation3D(rotateAxis, angleDeltaFactor * (upDown ? -1 : 1)); rt3d.Rotation = rotate; Matrix3D matrix = rt3d.Value; Point3D newPostition = matrix.Transform(camera.Position); camera.Position = newPostition; camera.LookDirection = new Vector3D(-newPostition.X, -newPostition.Y, -newPostition.Z); //update the up direction Vector3D newUpDirection = Vector3D.CrossProduct(camera.LookDirection, rotateAxis); newUpDirection.Normalize(); camera.UpDirection = newUpDirection; }
水平变换： private void HorizontalTransform(bool leftRight, double angleDeltaFactor) { Vector3D postion = new Vector3D(camera.Position.X, camera.Position.Y, camera.Position.Z); Vector3D rotateAxis = camera.UpDirection; RotateTransform3D rt3d = new RotateTransform3D(); AxisAngleRotation3D rotate = new AxisAngleRotation3D(rotateAxis, angleDeltaFactor * (leftRight ? -1 : 1)); rt3d.Rotation = rotate; Matrix3D matrix = rt3d.Value; Point3D newPostition = matrix.Transform(camera.Position); camera.Position = newPostition; camera.LookDirection = new Vector3D(-newPostition.X, -newPostition.Y, -newPostition.Z); }
最后还有一个鼠标滚轮调节视距的变换，如下：
private void Viewport3D_MouseWheel(object sender, MouseWheelEventArgs e) { double scaleFactor = 3; //120 near , -120 far System.Diagnostics.Debug.WriteLine(e.Delta.ToString()); Point3D currentPosition = camera.Position; Vector3D lookDirection = camera.LookDirection;//new Vector3D(camera.LookDirection.X, camera.LookDirection.Y, camera.LookDirection.Z); lookDirection.Normalize(); lookDirection *= scaleFactor; if (e.Delta == 120)//getting near { if ((currentPosition.X + lookDirection.X) * currentPosition.X > 0) { currentPosition += lookDirection; } }
if (e.Delta == -120)//getting far { currentPosition -= lookDirection; } Point3DAnimation positionAnimation = new Point3DAnimation(); positionAnimation.BeginTime = new TimeSpan(0, 0, 0); positionAnimation.Duration = TimeSpan.FromMilliseconds(100); positionAnimation.To = currentPosition; positionAnimation.From = camera.Position; positionAnimation.Completed += new EventHandler(positionAnimation_Completed); camera.BeginAnimation(PerspectiveCamera.PositionProperty, positionAnimation, HandoffBehavior.Compose); }
有了这个小程序之后，我们以后如果需要制作WPF 3D实体，也可以通过它来360度全方位地观测构建的3D实体。