Software Designer

引言

WPF使用了DirectX作为图形渲染引擎，因此游戏性能的表现要强于GDI+，而且WPF内建的对动画的支持使得游戏的编写更加简化。

WPF也提供3D图形的功能，不过3D的建模和动画比较复杂，这里先做一个2D的游戏引擎练练手。

实例

一直想做一个超级马里奥的游戏，就从这个游戏做起，画了一部分图，已经完成的有走动、跳跃、发射子弹、边界检查和场景滚动，没有关卡，没有敌人。

下面是游戏截图：

实现

行走中迈腿摆臂的动画是通过切换图片帧来实现的，切换帧有两种方法，一种是放一个Image，然后用ObjectAnimationUsingKeyFrames来改变Image的Source属性：

XAML代码

        <Storyboard x:Key="walkLeftStoryboard">
            <ObjectAnimationUsingKeyFrames Duration="00:00:00.4" RepeatBehavior="Forever"
                                           Storyboard.TargetName="marioImage" Storyboard.TargetProperty="Source" />
        </Storyboard>

        <Image Name="marioImage">
            <Image.RenderTransform>
                <TranslateTransform x:Name="marioTranslate"  X="0" Y="0"/>
            </Image.RenderTransform>
        </Image>

 

然后用C#代码添加帧： 

代码

        public static System.Drawing.Bitmap LoadBitmap(Uri uri)
        {
            StreamResourceInfo info = Application.GetResourceStream(uri);
            return new System.Drawing.Bitmap(info.Stream);
        }

        public static BitmapSource CreateBitmapSource(System.Drawing.Bitmap frame)
        {
            BitmapSource bs = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(
              frame.GetHbitmap(), IntPtr.Zero, Int32Rect.Empty, BitmapSizeOptions.FromEmptyOptions());
            return bs;
        }

        internal static void AddKeyFrames(ObjectAnimationUsingKeyFrames animation, params System.Drawing.Bitmap[] frames)
        {
            double percent = 0;
            double pace = 1.0 / frames.Length;
            foreach (var frame in frames)
            {
                BitmapSource bs = CreateBitmapSource(frame);
                animation.KeyFrames.Add(new DiscreteObjectKeyFrame(bs, KeyTime.FromPercent(percent)));
                percent += pace;
            }
        }

使用这种方法需要先把大图在代码里切割成四个小图，由于要用到System.Drawing所以代码不能迁移到Silverlight。

于是我又想了第二种方法，用ImageBrush做控件背景，然后用ObjectAnimationUsingKeyFrames来切换它的ViewBox。  

代码

        <Storyboard x:Key="walkLeftStoryboard">
            <ObjectAnimationUsingKeyFrames Duration="00:00:00.4" RepeatBehavior="Forever"
                                           Storyboard.TargetName="marioImage" Storyboard.TargetProperty="CurrentFrame" />
        </Storyboard>

        <game:AnimatedImage x:Name="marioImage" Image="/SuperMario;component/Images/mario.png" CurrentFrame="0, 0, 0.5, 0.5" Width="134" Height="131">
            <game:AnimatedImage.RenderTransform>
                <TranslateTransform x:Name="marioTranslate"  X="0" Y="0"/>
            </game:AnimatedImage.RenderTransform>
        </game:AnimatedImage>

用C#代码添加帧：

代码

        internal static void AddKeyFrames(ObjectAnimationUsingKeyFrames animation, Rect[] frames)
        {
            double percent = 0;
            double pace = 1.0 / frames.Length;
            foreach (var frame in frames)
            {
                animation.KeyFrames.Add(new DiscreteObjectKeyFrame(frame, KeyTime.FromPercent(percent)));
                percent += pace;
            }
        }

 AnimatedImage是一个自定义的控件，控件模板如下： 

    <Style TargetType="local:AnimatedImage">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="local:AnimatedImage">
                    <Border BorderThickness="0">
                        <Border.Background>
                            <ImageBrush ImageSource="{Binding Path=Image,RelativeSource={RelativeSource TemplatedParent}}"
                                        Stretch="UniformToFill" AlignmentX="Left" AlignmentY="Top" Viewbox="{Binding Path=CurrentFrame,RelativeSource={RelativeSource TemplatedParent}}"/>
                        </Border.Background>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

后来发现SliverLight里的TileBrush没有ViewBox属性，所以还是无法迁移。

 

接下来就是在GameLoop中根据键盘按键控制动画的开始和停止，并用marioTranslate来改变人物的位置。

GameLoop可由CompositionTarget.Rendering事件指定：

        GameLoop gameLoop;
        private void Window_Loaded(object sender, RoutedEventArgs e)
        {       
            ......
            gameLoop = new GameLoop(player, Scenes.Level1);
            CompositionTarget.Rendering += new EventHandler(CompositionTarget_Rendering);
        }

        void CompositionTarget_Rendering(object sender, EventArgs e)
        {
            gameLoop.ProcessChanges();
        }

  

在GameLoop中还需要注意的就是跳跃过程中重力效果的模拟和对物体、台阶、边界的碰撞检查，这个就不多说了，看代码：

代码

        public void ProcessChanges()
        {
            TimeSpan timeSpan = DateTime.Now - lastTime;
            double step = timeSpan.TotalSeconds;
            lastTime = DateTime.Now;

            double x = Sprite.X;
            double y = Sprite.Y;
            double dx = step * Sprite.Speed;
            if (Sprite.IsWalkingLeft)
            {
                x -= dx;
                Scene.ScrollRightt(x, dx);
            }
            else if (Sprite.IsWalkingRight)
            {
                x += dx;
                Scene.ScrollLeft(x, dx);
            }
            if (Map.CanMoveTo(x, Sprite.Y, Sprite.Width, Sprite.Height))
            {
                Sprite.X = x;
            }

            if (Sprite.IsJumping)
            {
                y -= (1 - Sprite.JumpTime) * step * 400;
                if (Sprite.JumpTime < 1 && Map.CanMoveTo(Sprite.X, y, Sprite.Width, Sprite.Height))
                {
                    Sprite.Y = y;
                    Sprite.JumpTime += step;
                }
                else
                {
                    Sprite.IsJumping = false;
                    Sprite.IsFalling = true;
                    Sprite.JumpTime = 0;
                }
            }
            else if (Sprite.IsFalling)
            {
                y += 800 * Sprite.FallTime * step;
                if (Map.CanMoveTo(Sprite.X, y, Sprite.Width, Sprite.Height))
                {
                    Sprite.Y = y;
                    Sprite.FallTime += step;
                }
                else
                {
                    Sprite.IsFalling = false;
                    Sprite.FallTime = 0;
                }
            }
            else
            {
                y += 1;
                if (Map.CanMoveTo(Sprite.X, y, Sprite.Width, Sprite.Height))
                {
                    Sprite.Y = y;
                    Sprite.IsFalling = true;
                    Sprite.FallTime = step;
                }
            }
        }

 

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