WPF 3D：簡單的Point3D和Vector3D動畫創造一個旋轉的正方體

運作結果：

事實上很簡單，定義好一個正方體，處理好紋理。關于MeshGeometry3D的正确定義和紋理這裡就不多講了，可以參考我以前寫過的一些文章：

<a href="http://www.cnblogs.com/mgen/archive/2012/02/22/2363151.html">WPF 3D: MeshGeometry3D紋理坐标的正确定義</a>

<a href="http://www.cnblogs.com/mgen/archive/2012/02/26/2368851.html">WPF 3D：MeshGeometry3D的定義和光照</a>

接下來就是怎樣讓它動起來。我們通過3D點動畫來改變照相機（Camera類型）的位置（Position屬性）進而使正方體動起來（這樣的話實際上正方體沒動，而是照相機在動）。由于正方體是水準旋轉的，那麼Y軸可以忽略，參考下面整個3D圖形的俯視圖，動畫是這樣進行的：

我們的照相機初始時放置在Z軸(0,0,5)的位置，如下圖：

是以旋轉照相機隻需要把Position屬性調整到相應的點就可以，分别是0,0,5 5,0,0 0,0,-5 –5,0,0 ，如下代碼：

&lt;Point3DAnimationUsingKeyFrames Storyboard.TargetProperty="Position"

                               Storyboard.TargetName="camera"&gt;

    &lt;LinearPoint3DKeyFrame KeyTime="0:0:1" Value="5

0 0"/&gt;

    &lt;LinearPoint3DKeyFrame KeyTime="0:0:2" Value="0

0 -5"/&gt;

    &lt;LinearPoint3DKeyFrame KeyTime="0:0:3" Value="-5

    &lt;LinearPoint3DKeyFrame KeyTime="0:0:4" Value="0

0 5"/&gt;

&lt;/Point3DAnimationUsingKeyFrames&gt;

注意上面使用的是Point3DAnimation類型。接下來需要注意的，我們還需要調整照相機的方向（Camera類型的LookDirection屬性），否則照相機還會保持原方向。這個屬性類型是3D向量，是以需要用Vector3DAnimation類型，調整向量也很簡單，隻需要根據照相機的移動點把方向調整到中心點。

如下代碼：

&lt;Vector3DAnimationUsingKeyFrames Storyboard.TargetProperty="LookDirection"

                                Storyboard.TargetName="camera"&gt;

    &lt;LinearVector3DKeyFrame KeyTime="0:0:1" Value="-1

    &lt;LinearVector3DKeyFrame KeyTime="0:0:2" Value="0

0 1"/&gt;

    &lt;LinearVector3DKeyFrame KeyTime="0:0:3" Value="1

    &lt;LinearVector3DKeyFrame KeyTime="0:0:4" Value="0

0 -1"/&gt;

&lt;/Vector3DAnimationUsingKeyFrames&gt;

當運作動畫時，你會發現等方塊背面轉過來後，它還保持這暗色，原因是整個光照沒有被旋轉。是以最好把光照再旋轉一下就趨近完美了，在動畫中再調節DirectionalLight的Direction屬性就可以了，這個也是Vector3D類型。

下面是完整的XAML代碼：

&lt;Viewport3D&gt;

    &lt;Viewport3D.Triggers&gt;

        &lt;EventTrigger RoutedEvent="Loaded"&gt;

            &lt;BeginStoryboard&gt;

                &lt;Storyboard RepeatBehavior="Forever"&gt;

                    &lt;Point3DAnimationUsingKeyFrames Storyboard.TargetProperty="Position"

                                                   Storyboard.TargetName="camera"&gt;

                        &lt;LinearPoint3DKeyFrame KeyTime="0:0:1" Value="5

                        &lt;LinearPoint3DKeyFrame KeyTime="0:0:2" Value="0

                        &lt;LinearPoint3DKeyFrame KeyTime="0:0:3" Value="-5

                        &lt;LinearPoint3DKeyFrame KeyTime="0:0:4" Value="0

                    &lt;/Point3DAnimationUsingKeyFrames&gt;

                    &lt;Vector3DAnimationUsingKeyFrames Storyboard.TargetProperty="LookDirection"

                                                    Storyboard.TargetName="camera"&gt;

                        &lt;LinearVector3DKeyFrame KeyTime="0:0:1" Value="-1

                        &lt;LinearVector3DKeyFrame KeyTime="0:0:2" Value="0

                        &lt;LinearVector3DKeyFrame KeyTime="0:0:3" Value="1

                        &lt;LinearVector3DKeyFrame KeyTime="0:0:4" Value="0

                    &lt;/Vector3DAnimationUsingKeyFrames&gt;

                    &lt;Vector3DAnimationUsingKeyFrames Storyboard.TargetProperty="Direction"

                                                    Storyboard.TargetName="light"&gt;

                &lt;/Storyboard&gt;

            &lt;/BeginStoryboard&gt;

        &lt;/EventTrigger&gt;

    &lt;/Viewport3D.Triggers&gt;

    &lt;Viewport3D.Camera&gt;

        &lt;PerspectiveCamera x:Name="camera" Position="0

0 5" LookDirection="0 0 -1"FieldOfView="60"/&gt;

    &lt;/Viewport3D.Camera&gt;

    &lt;ModelVisual3D&gt;

        &lt;ModelVisual3D.Content&gt;

            &lt;Model3DGroup&gt;

                &lt;DirectionalLight Direction="0

0 -1"

                                 x:Name="light"

                                 Color="White"/&gt;

                &lt;GeometryModel3D&gt;

                    &lt;GeometryModel3D.Geometry&gt;

                        &lt;MeshGeometry3D Positions="-1

1 1, 1 1 1, -1 -1 1, 1 -1 1, -1 1 -1, 1 1 -1, -1 -1 -1, 1 -1 -1

                                                    1 1 1, 1 1 -1, 1 -1 1, 1 -1 -1, -1 1 1, -1 1 -1, -1 -1 1, -1 -1 -1

                                                   -1 1 1, -1 1 -1, 1 1 1, 1 1 -1, -1 -1 1, -1 -1 -1, 1 -1 1, 1 -1 -1"

                                       TriangleIndices="0

2 1, 1 2 3, 5 6 4, 5 7 6

                                                         8 10 9, 9 10 11, 13 14 12, 13 15 14

                                                         16 18 17, 17 18 19, 22 21 20, 22 23 21"

                                       TextureCoordinates="0

0, 1 0, 0 1, 1 1,

                                                            0 0, 1 0, 0 1, 1 1,

                                                            0 0, 1 0, 0 1, 1 1" /&gt;

                    &lt;/GeometryModel3D.Geometry&gt;

                    &lt;GeometryModel3D.Material&gt;

                        &lt;DiffuseMaterial&gt;

                            &lt;DiffuseMaterial.Brush&gt;

                                &lt;LinearGradientBrush StartPoint="0,0" EndPoint="1,0"&gt;

                                    &lt;GradientStop Color="YellowGreen" Offset="0"/&gt;

                                    &lt;GradientStop Color="Green" Offset="1"/&gt;

                                &lt;/LinearGradientBrush&gt;

                            &lt;/DiffuseMaterial.Brush&gt;

                        &lt;/DiffuseMaterial&gt;

                    &lt;/GeometryModel3D.Material&gt;

                &lt;/GeometryModel3D&gt;

            &lt;/Model3DGroup&gt;

        &lt;/ModelVisual3D.Content&gt;

    &lt;/ModelVisual3D&gt;

&lt;/Viewport3D&gt;