WPF 3D变换应用

 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：

 <Viewport3D>
        <Viewport3D.Camera>
            <!--<camera Position="15,15,15" LookDirection="-1,-1,-1" Width="15"></camera>-->
            <!--<camera Position="-5,-5,-5" LookDirection="1,1,1" Width="10" x:Name="camera"></camera>-->
            <!--<PerspectiveCamera Position="-5,-5,-5" LookDirection="1 1 1" FieldOfView="90"></PerspectiveCamera>-->
            <!--<PerspectiveCamera Position="-4,-4,-4" LookDirection="1 1 1" FieldOfView="75" x:Name="camera"></PerspectiveCamera>-->
            <PerspectiveCamera Position="8,8,8" LookDirection="-1 -1 -1" FieldOfView="75" UpDirection="-1 1 -1" x:Name="camera"></PerspectiveCamera>
        </Viewport3D.Camera>
        <Viewport3D.Children>
            <ModelVisual3D x:Name="light">
                <ModelVisual3D.Content>
                    <AmbientLight />
                </ModelVisual3D.Content>
            </ModelVisual3D>
            <ModelVisual3D x:Name="magicCube">
                <ModelVisual3D.Content>
                    <!--    0: 0,0,0    1: 0,0,2    2: 2,0,2    3: 2,0,0    4: 2,2,0    5: 0,2,0    6: 0,2,2    7: 2,2,2    -->
                    <Model3DGroup x:Name="cube">
                        <Model3DGroup.Transform>
                            <TranslateTransform3D OffsetX="-1" OffsetY="-1" OffsetZ="-1" />
                        </Model3DGroup.Transform>
                        <!--F1: 0,3,2,1-->
                        <GeometryModel3D x:Name="F1">
                            <GeometryModel3D.Material>
                                <DiffuseMaterial Brush="Blue"/>
                            </GeometryModel3D.Material>
                            <GeometryModel3D.Geometry>
                                <MeshGeometry3D Positions="0,0,0 2,0,0 2,0,2 0,0,2" TriangleIndices="0,1,2 0,2,3"></MeshGeometry3D>
                            </GeometryModel3D.Geometry>
                        </GeometryModel3D>
                        <!--F2: 0,1,6,5-->
                        <GeometryModel3D x:Name="F2">
                            <GeometryModel3D.Material>
                                <DiffuseMaterial Brush="Green"/>
                            </GeometryModel3D.Material>
                            <GeometryModel3D.Geometry>
                                <MeshGeometry3D Positions="0,0,0 0,0,2 0,2,2 0,2,0" TriangleIndices="0 1 2 0 2 3"></MeshGeometry3D>
                            </GeometryModel3D.Geometry>
                        </GeometryModel3D>
                        <!--F3: 4,5,6,7-->
                        <GeometryModel3D x:Name="F3">
                            <GeometryModel3D.Material>
                                <DiffuseMaterial Brush="Red"/>
                            </GeometryModel3D.Material>
                            <GeometryModel3D.Geometry>
                                <MeshGeometry3D Positions="2,2,0 0,2,0 0,2,2 2,2,2" TriangleIndices="0 1 2 0 2 3"></MeshGeometry3D>
                            </GeometryModel3D.Geometry>
                        </GeometryModel3D>
                        <!--F4: 2,3,4,7-->
                        <GeometryModel3D x:Name="F4">
                            <GeometryModel3D.Material>
                                <!--<DiffuseMaterial>
                                    <DiffuseMaterial.Brush>
                                        <VisualBrush>
                                            <VisualBrush.Visual>
                                                <Image Source="cubesurface.jpg">
                                                    <Image.Style>
                                                        <Style>
                                                            <Setter Property="Image.Opacity" Value="0.6"></Setter>
                                                        </Style>
                                                    </Image.Style>
                                                </Image>
                                            </VisualBrush.Visual>
                                        </VisualBrush>
                                    </DiffuseMaterial.Brush>
                                </DiffuseMaterial>-->
                                <DiffuseMaterial Brush="Yellow"/>
                            </GeometryModel3D.Material>
                                
                            <GeometryModel3D.Geometry>
                                <MeshGeometry3D Positions="2,0,2 2,0,0 2,2,0 2,2,2" TriangleIndices="0 1 2 0 2 3" TextureCoordinates="0,0 0,1 1,1 1,0">
                                </MeshGeometry3D>
                            </GeometryModel3D.Geometry>
                        </GeometryModel3D>
                        <!--F5: 1,2,7,6-->
                        <GeometryModel3D x:Name="F5">
                            <GeometryModel3D.Material>
                                <DiffuseMaterial Brush="White"/>
                            </GeometryModel3D.Material>
                            <GeometryModel3D.Geometry>
                                <MeshGeometry3D Positions=" 0,0,2 2,0,2 2,2,2 0,2,2" TriangleIndices="0 1 2 0 2 3"></MeshGeometry3D>
                            </GeometryModel3D.Geometry>
                        </GeometryModel3D>
                        <!--F6: 0,5,4,3-->
                        <GeometryModel3D x:Name="F6">
                            <GeometryModel3D.Material>
                                <DiffuseMaterial Brush="Orange"/>
                            </GeometryModel3D.Material>
                            <GeometryModel3D.Geometry>
                                <MeshGeometry3D Positions=" 0,0,0 0,2,0 2,2,0 2,0,0" TriangleIndices="0 1 2 0 2 3"></MeshGeometry3D>
                            </GeometryModel3D.Geometry>
                        </GeometryModel3D>
                    </Model3DGroup>
                </ModelVisual3D.Content>
            </ModelVisual3D>
        </Viewport3D.Children>
    </Viewport3D>

         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。

 

<Window x:Class="MagicCube.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="295" Width="525" Background="Black"
        MouseMove="Viewport3D_MouseMove"
        MouseLeftButtonDown="Viewport3D_MouseLeftButtonDown"
        MouseWheel="Viewport3D_MouseWheel"
        KeyDown="Window_KeyDown">
    <Viewport3D …>
</Window>

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。

演示程序 源代码