原文:

        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。

有关3D的基础知识可以参考MSDN文档：

 

 

        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>

        <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 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。