Question

我在MonoGame（Xna克隆到Mac）中制作的游戏需要使用Bloom效果。我在MSDN（http://xbox.create.msdn.com/en-US/education/catalog/sample/bloom）上跟踪了示例中的代码。当我把这个效果放到我的2D游戏中时，它使背景变成蓝色的靛蓝紫色。我在谷歌周围看了解为什么会这样，我不知道为什么。我找不到答案。我发现了this StackOverflow的问题，他们说了一些关于Pre-Bloom的内容，我猜这就是这个问题。我把我的绘图代码放在一个组件中。我的抽奖代码是：

    spriteBatch.Begin();
((Pump)Game).bloomComponent.BeginDraw();
grid.DrawPeices(spriteBatch);
    spriteBatch.End();

DrawPeices方法只是遍历一个列表并正常绘制每个精灵。我在我的主Game类中初始化组件的BloomComponent类是：

#region File Description
//-----------------------------------------------------------------------------
// BloomComponent.cs
//
// Microsoft XNA Community Game Platform
// Copyright (C) Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------
#endregion

#region Using Statements
using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;
using System.IO;
using System.Reflection;
#endregion

namespace Pump.Libraries.Bloom
{
public class BloomComponent : DrawableGameComponent
{
    #region Fields

    SpriteBatch spriteBatch;

    Effect bloomExtractEffect;
    Effect bloomCombineEffect;
    Effect gaussianBlurEffect;

    RenderTarget2D sceneRenderTarget;
    RenderTarget2D renderTarget1;
    RenderTarget2D renderTarget2;
    RenderTarget2D finalRenderTarget;
    public RenderTarget2D FinalRenderTarget { get { return finalRenderTarget; } }

    byte[] shaderCode;


    // Choose what display settings the bloom should use.
    public BloomSettings Settings
    {
        get { return settings; }
        set { settings = value; }
    }

    BloomSettings settings = BloomSettings.PresetSettings[0];


    // Optionally displays one of the intermediate buffers used
    // by the bloom postprocess, so you can see exactly what is
    // being drawn into each rendertarget.
    public enum IntermediateBuffer
    {
        PreBloom,
        BlurredHorizontally,
        BlurredBothWays,
        FinalResult,
    }

    public IntermediateBuffer ShowBuffer
    {
        get { return showBuffer; }
        set { showBuffer = value; }
    }

    IntermediateBuffer showBuffer = IntermediateBuffer.FinalResult;


    #endregion

    #region Initialization


    public BloomComponent(Game game)
        : base(game)
    {
        if (game == null)
            throw new ArgumentNullException("game");
    }


    /// <summary>
    /// Load your graphics content.
    /// </summary>
    protected override void LoadContent()
    {
        spriteBatch = new SpriteBatch(GraphicsDevice);
        //LOAD ALL THE SHADERS
        var assembly = Assembly.GetExecutingAssembly();

        var stream = assembly.GetManifestResourceStream("Pump.Shaders.BloomExtract.mgfxo");

        using (var ms = new MemoryStream())
        {
            stream.CopyTo(ms);
            shaderCode = ms.ToArray();
        }

        stream.Close();
        bloomExtractEffect = new Effect(GraphicsDevice, shaderCode);
        assembly = Assembly.GetExecutingAssembly();

        stream = assembly.GetManifestResourceStream("Pump.Shaders.BloomCombine.mgfxo");

        using (var ms = new MemoryStream())
        {
            stream.CopyTo(ms);
            shaderCode = ms.ToArray();
        }

        stream.Close();
        bloomCombineEffect = new Effect(GraphicsDevice, shaderCode);
        assembly = Assembly.GetExecutingAssembly();

        stream = assembly.GetManifestResourceStream("Pump.Shaders.GaussianBlur.mgfxo");

        using (var ms = new MemoryStream())
        {
            stream.CopyTo(ms);
            shaderCode = ms.ToArray();
        }

        stream.Close();
        gaussianBlurEffect = new Effect(GraphicsDevice, shaderCode);

        /*bloomExtractEffect = Game.Content.Load<Effect>("BloomExtract");
        bloomCombineEffect = Game.Content.Load<Effect>("BloomCombine");
        gaussianBlurEffect = Game.Content.Load<Effect>("GaussianBlur");*/

        // Look up the resolution and format of our main backbuffer.
        PresentationParameters pp = GraphicsDevice.PresentationParameters;

        int width = pp.BackBufferWidth;
        int height = pp.BackBufferHeight;

        SurfaceFormat format = pp.BackBufferFormat;

        // Create a texture for rendering the main scene, prior to applying bloom.
        sceneRenderTarget = new RenderTarget2D(GraphicsDevice, width, height, false,
                                               format, pp.DepthStencilFormat, pp.MultiSampleCount,
                                               RenderTargetUsage.DiscardContents);
        finalRenderTarget = new RenderTarget2D(GraphicsDevice, width, height, false,
                                               format, pp.DepthStencilFormat, pp.MultiSampleCount,
                                               RenderTargetUsage.DiscardContents);

        // Create two rendertargets for the bloom processing. These are half the
        // size of the backbuffer, in order to minimize fillrate costs. Reducing
        // the resolution in this way doesn't hurt quality, because we are going
        // to be blurring the bloom images in any case.
        width /= 2;
        height /= 2;

        renderTarget1 = new RenderTarget2D(GraphicsDevice, width, height, false, format, DepthFormat.None);
        renderTarget2 = new RenderTarget2D(GraphicsDevice, width, height, false, format, DepthFormat.None);
    }


    /// <summary>
    /// Unload your graphics content.
    /// </summary>
    protected override void UnloadContent()
    {
        sceneRenderTarget.Dispose();
        renderTarget1.Dispose();
        renderTarget2.Dispose();
    }


    #endregion

    #region Draw


    /// <summary>
    /// This should be called at the very start of the scene rendering. The bloom
    /// component uses it to redirect drawing into its custom rendertarget, so it
    /// can capture the scene image in preparation for applying the bloom filter.
    /// </summary>
    public void BeginDraw()
    {
        if (Visible)
        {
            GraphicsDevice.SetRenderTarget(sceneRenderTarget);
        }
    }


    /// <summary>
    /// This is where it all happens. Grabs a scene that has already been rendered,
    /// and uses postprocess magic to add a glowing bloom effect over the top of it.
    /// </summary>
    public override void Draw(GameTime gameTime)
    {
        GraphicsDevice.SamplerStates[1] = SamplerState.LinearClamp;

        // Pass 1: draw the scene into rendertarget 1, using a
        // shader that extracts only the brightest parts of the image.
        bloomExtractEffect.Parameters["BloomThreshold"].SetValue(
            Settings.BloomThreshold);

        DrawFullscreenQuad(sceneRenderTarget, renderTarget1,
                           bloomExtractEffect,
                           IntermediateBuffer.PreBloom);

        // Pass 2: draw from rendertarget 1 into rendertarget 2,
        // using a shader to apply a horizontal gaussian blur filter.
        SetBlurEffectParameters(1.0f / (float)renderTarget1.Width, 0);

        DrawFullscreenQuad(renderTarget1, renderTarget2,
                           gaussianBlurEffect,
                           IntermediateBuffer.BlurredHorizontally);

        // Pass 3: draw from rendertarget 2 back into rendertarget 1,
        // using a shader to apply a vertical gaussian blur filter.
        SetBlurEffectParameters(0, 1.0f / (float)renderTarget1.Height);

        DrawFullscreenQuad(renderTarget2, renderTarget1,
                           gaussianBlurEffect,
                           IntermediateBuffer.BlurredBothWays);

        // Pass 4: draw both rendertarget 1 and the original scene
        // image back into the main backbuffer, using a shader that
        // combines them to produce the final bloomed result.
        GraphicsDevice.SetRenderTarget(null);

        EffectParameterCollection parameters = bloomCombineEffect.Parameters;

        parameters["BloomIntensity"].SetValue(Settings.BloomIntensity);
        parameters["BaseIntensity"].SetValue(Settings.BaseIntensity);
        parameters["BloomSaturation"].SetValue(Settings.BloomSaturation);
        parameters["BaseSaturation"].SetValue(Settings.BaseSaturation);

        GraphicsDevice.Textures[1] = sceneRenderTarget;

        Viewport viewport = GraphicsDevice.Viewport;

        DrawFullscreenQuad(renderTarget1,
                           viewport.Width, viewport.Height,
                           bloomCombineEffect,
                           IntermediateBuffer.FinalResult);
    }


    /// <summary>
    /// Helper for drawing a texture into a rendertarget, using
    /// a custom shader to apply postprocessing effects.
    /// </summary>
    void DrawFullscreenQuad(Texture2D texture, RenderTarget2D renderTarget,
                            Effect effect, IntermediateBuffer currentBuffer)
    {
        GraphicsDevice.SetRenderTarget(renderTarget);

        DrawFullscreenQuad(texture,
                           renderTarget.Width, renderTarget.Height,
                           effect, currentBuffer);
    }


    /// <summary>
    /// Helper for drawing a texture into the current rendertarget,
    /// using a custom shader to apply postprocessing effects.
    /// </summary>
    void DrawFullscreenQuad(Texture2D texture, int width, int height,
                            Effect effect, IntermediateBuffer currentBuffer)
    {
        // If the user has selected one of the show intermediate buffer options,
        // we still draw the quad to make sure the image will end up on the screen,
        // but might need to skip applying the custom pixel shader.
        if (showBuffer < currentBuffer)
        {
            effect = null;
        }

        spriteBatch.Begin(0, BlendState.Opaque, null, null, null, effect);
        spriteBatch.Draw(texture, new Rectangle(0, 0, width, height), Color.White);
        spriteBatch.End();
    }


    /// <summary>
    /// Computes sample weightings and texture coordinate offsets
    /// for one pass of a separable gaussian blur filter.
    /// </summary>
    void SetBlurEffectParameters(float dx, float dy)
    {
        // Look up the sample weight and offset effect parameters.
        EffectParameter weightsParameter, offsetsParameter;

        weightsParameter = gaussianBlurEffect.Parameters["SampleWeights"];
        offsetsParameter = gaussianBlurEffect.Parameters["SampleOffsets"];

        // Look up how many samples our gaussian blur effect supports.
        int sampleCount = weightsParameter.Elements.Count;

        // Create temporary arrays for computing our filter settings.
        float[] sampleWeights = new float[sampleCount];
        Vector2[] sampleOffsets = new Vector2[sampleCount];

        // The first sample always has a zero offset.
        sampleWeights[0] = ComputeGaussian(0);
        sampleOffsets[0] = new Vector2(0);

        // Maintain a sum of all the weighting values.
        float totalWeights = sampleWeights[0];

        // Add pairs of additional sample taps, positioned
        // along a line in both directions from the center.
        for (int i = 0; i < sampleCount / 2; i++)
        {
            // Store weights for the positive and negative taps.
            float weight = ComputeGaussian(i + 1);

            sampleWeights[i * 2 + 1] = weight;
            sampleWeights[i * 2 + 2] = weight;

            totalWeights += weight * 2;

            // To get the maximum amount of blurring from a limited number of
            // pixel shader samples, we take advantage of the bilinear filtering
            // hardware inside the texture fetch unit. If we position our texture
            // coordinates exactly halfway between two texels, the filtering unit
            // will average them for us, giving two samples for the price of one.
            // This allows us to step in units of two texels per sample, rather
            // than just one at a time. The 1.5 offset kicks things off by
            // positioning us nicely in between two texels.
            float sampleOffset = i * 2 + 1.5f;

            Vector2 delta = new Vector2(dx, dy) * sampleOffset;

            // Store texture coordinate offsets for the positive and negative taps.
            sampleOffsets[i * 2 + 1] = delta;
            sampleOffsets[i * 2 + 2] = -delta;
        }

        // Normalize the list of sample weightings, so they will always sum to one.
        for (int i = 0; i < sampleWeights.Length; i++)
        {
            sampleWeights[i] /= totalWeights;
        }

        // Tell the effect about our new filter settings.
        weightsParameter.SetValue(sampleWeights);
        offsetsParameter.SetValue(sampleOffsets);
    }


    /// <summary>
    /// Evaluates a single point on the gaussian falloff curve.
    /// Used for setting up the blur filter weightings.
    /// </summary>
    float ComputeGaussian(float n)
    {
        float theta = Settings.BlurAmount;

        return (float)((1.0 / Math.Sqrt(2 * Math.PI * theta)) *
                       Math.Exp(-(n * n) / (2 * theta * theta)));
    }


    #endregion
}
}

最后，BloomSettings.cs：

#region File Description
//-----------------------------------------------------------------------------
// BloomSettings.cs
//
// Microsoft XNA Community Game Platform
// Copyright (C) Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------
#endregion

namespace Pump.Libraries.Bloom
{
/// <summary>
/// Class holds all the settings used to tweak the bloom effect.
/// </summary>
public class BloomSettings
{
    #region Fields


    // Name of a preset bloom setting, for display to the user.
    public readonly string Name;


    // Controls how bright a pixel needs to be before it will bloom.
    // Zero makes everything bloom equally, while higher values select
    // only brighter colors. Somewhere between 0.25 and 0.5 is good.
    public readonly float BloomThreshold;


    // Controls how much blurring is applied to the bloom image.
    // The typical range is from 1 up to 10 or so.
    public readonly float BlurAmount;


    // Controls the amount of the bloom and base images that
    // will be mixed into the final scene. Range 0 to 1.
    public readonly float BloomIntensity;
    public readonly float BaseIntensity;


    // Independently control the color saturation of the bloom and
    // base images. Zero is totally desaturated, 1.0 leaves saturation
    // unchanged, while higher values increase the saturation level.
    public readonly float BloomSaturation;
    public readonly float BaseSaturation;


    #endregion


    /// <summary>
    /// Constructs a new bloom settings descriptor.
    /// </summary>
    public BloomSettings(string name, float bloomThreshold, float blurAmount,
                         float bloomIntensity, float baseIntensity,
                         float bloomSaturation, float baseSaturation)
    {
        Name = name;
        BloomThreshold = bloomThreshold;
        BlurAmount = blurAmount;
        BloomIntensity = bloomIntensity;
        BaseIntensity = baseIntensity;
        BloomSaturation = bloomSaturation;
        BaseSaturation = baseSaturation;
    }


    /// <summary>
    /// Table of preset bloom settings, used by the sample program.
    /// </summary>
    public static BloomSettings[] PresetSettings =
    {
        //                Name           Thresh  Blur Bloom  Base  BloomSat BaseSat
        new BloomSettings("Default",     0.25f,  4,   1.25f, 1,    1,       1),
        new BloomSettings("Soft",        0,      3,   1,     1,    1,       1),
        new BloomSettings("Desaturated", 0.5f,   8,   2,     1,    0,       1),
        new BloomSettings("Saturated",   0.25f,  4,   2,     1,    2,       0),
        new BloomSettings("Blurry",      0,      2,   1,     0.1f, 1,       1),
        new BloomSettings("Subtle",      0.5f,   2,   1,     1,    1,       1),
    };
}
}

有人可以解释为什么屏幕是蓝色/靛蓝，以及我如何解决它？如果你需要知道，我原来的背景是黑色的。哦，我有一个截图： Bloom Purple Screen

Answer 1

在查看截图和代码时，您确实没有清除渲染，我会修改您的BeginDraw代码以调用Clear，以便在您绘制目标之前将目标初始化为已知值。

/// <summary>
/// This should be called at the very start of the scene rendering. The bloom
/// component uses it to redirect drawing into its custom rendertarget, so it
/// can capture the scene image in preparation for applying the bloom filter.
/// </summary>
public void BeginDraw()
{
    if (Visible)
    {
        GraphicsDevice.SetRenderTarget(renderTarget1);
        GraphicsDevice.Clear(Color.Black);
        GraphicsDevice.SetRenderTarget(renderTarget2);
        GraphicsDevice.Clear(Color.Black);
        GraphicsDevice.SetRenderTarget(FinalRenderTarget);
        GraphicsDevice.Clear(Color.Black);
        GraphicsDevice.SetRenderTarget(sceneRenderTarget);
    }
}

使用Bloom效果使MonoGame（Xna）中的黑色背景为蓝色/靛蓝色

1 个答案: