Question

在XNA框架中，有没有办法使用典型的SpriteBatch方法渲染2D场景，然后在渲染帧后，将效果应用于整个图像？

例如，模糊，棕褐色甚至使整个事物看起来像旧电影，有颗粒，灰尘，线条等？

Answer 1

是的 - 您要做的是将渲染目标设置为渲染到纹理而不是图形硬件。然后，一旦输出在纹理中，您将应用像素着色器效果，并将其发送出去。

这里有一些很棒的基本样本效果（我衷心地建议订阅这个博客） http://blogs.msdn.com/b/shawnhar/archive/2007/05/23/transitions-part-four-rendertargets.aspx

Answer 2

这是我的发光代码，我会对如何改进它的评论感兴趣。基本上我有对象分为发光和正常。我在Initialize方法中创建了两个RenderTarget2D对象，其中一个带有深度缓冲区，因为我正在做3D：

GlowTarget = new RenderTarget2D(GraphicsDevice, pp.BackBufferWidth, pp.BackBufferHeight, true, SurfaceFormat.Color, DepthFormat.Depth24Stencil8);
GlowTarget2 = new RenderTarget2D(GraphicsDevice, pp.BackBufferWidth, pp.BackBufferHeight, true, SurfaceFormat.Color, DepthFormat.None);

在我的绘制方法中，我将常规对象渲染到我的GlowTarget，然后将颜色清除为黑色，使用零Alpha并绘制发光对象。我将此绘制到GlowTarget2，并应用自定义效果像素着色器以在X方向上模糊它。然后我清除渲染目标并绘制普通对象。最后，我在顶部绘制了GlowTarget2纹理，另一个自定义效果在Y方向上模糊。

/// <summary>
/// This is called when the game should draw itself.
/// </summary>
/// <param name="gameTime">Provides a snapshot of timing values.</param>
protected override void Draw(GameTime gameTime)
{
    // draw clear GlowTarget and draw normal, non-glowing objects to set depth buffer
    GraphicsDevice.SetRenderTarget(GlowTarget);
    GraphicsDevice.Clear(ClearOptions.DepthBuffer | ClearOptions.Stencil | ClearOptions.Target, Color.FromNonPremultiplied(0, 0, 0, 0), 1f, 0);
    MyScene.DrawNormal();

    // clear target only and set color to black WITH ZERO ALPHA, then draw glowing objects
    // so they will be the only ones that appear and they will be hidden by objects in front of them
    GraphicsDevice.Clear(ClearOptions.Target, Color.FromNonPremultiplied(0, 0, 0, 0), 1f, 0);
    MyScene.DrawGlow();

    // blur objects horizontally into GlowTarget2
    GraphicsDevice.SetRenderTarget(GlowTarget2);
    GraphicsDevice.Clear(Color.FromNonPremultiplied(0, 0, 0, 0));
    using (SpriteBatch sb = new SpriteBatch(GlowTarget2.GraphicsDevice))
    {
        blurXEffect.Parameters["PixelSize"].SetValue((float)(1.0f / (float)GlowTarget.Width));
        sb.Begin(0, BlendState.Additive, SamplerState.PointWrap, DepthStencilState.Default, RasterizerState.CullNone, blurXEffect);
        sb.Draw(GlowTarget, new Rectangle(GraphicsDevice.Viewport.X, GraphicsDevice.Viewport.Y, GraphicsDevice.Viewport.Width, GraphicsDevice.Viewport.Height), Color.White);
        sb.End();
    }

    // now reset context and clear for actual drawing
    GraphicsDevice.SetRenderTarget(null);
    GraphicsDevice.BlendState = BlendState.Opaque;
    GraphicsDevice.Clear(Color.Black);

    // TODO: Add your drawing code here
    base.Draw(gameTime);

    // draw scene to graphics card back buffer
    MyScene.DrawNormal();

    using (SpriteBatch sprite = new SpriteBatch(GraphicsDevice))
    {
        // draw glowing texture and blur Y this time
        blurYEffect.Parameters["PixelSize"].SetValue((float)(1.0f / (float)GlowTarget.Height));
        sprite.Begin(0, BlendState.Additive, SamplerState.PointWrap, DepthStencilState.Default, RasterizerState.CullNone, blurYEffect);

        //sprite.Draw(GlowTarget, new Vector2(0, 0), Color.White);
        sprite.Draw(GlowTarget2, new Rectangle(GraphicsDevice.Viewport.X, GraphicsDevice.Viewport.Y, GraphicsDevice.Viewport.Width, GraphicsDevice.Viewport.Height), Color.White);
        sprite.End();
    }
}

如果您正在使用2D做一些简单的事情，例如应用单个效果，那么您可以在SpriteBatch.Begin（）调用中设置自定义效果......这是我的模糊X的着色器：

// texture we are rendering
sampler2D tex : register(S0);

float PixelSize;

// pixel shader function
float4 main(float2 uv : TEXCOORD) : COLOR
{
    float4 c = 0; // will get max of each value for c
    float alpha = 0; // alpha will be average

    float2 myuv = uv;
    for(int i = -7; i <= 7; i++)
    {
        myuv.x = uv.x + (i * PixelSize * 1.5);
        float4 sample = tex2D(tex, myuv);
        c = max(c, sample);
        alpha += sample.a;
    }

    c.a = saturate(pow(abs(alpha / 6), 0.4));
    return(c);
}

technique Technique1
{
    pass Pass1
    {
        PixelShader = compile ps_2_0 main();
    }
}

这是一个示例图像，红绿蓝正方形，上面有发光版本： Glow Sample

将后渲染效果应用于XNA中的SpriteBatch

2 个答案: