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我正在尝试为我正在从事的项目编写 HLSL 像素着色器。基本上我想做的是，如果纹理有一个浮点值为 0.52 的像素（在 0-255 的比例上是 132.6），我想在 60% 的时间输出 133，在 40% 的时间输出 132。现在写我只是想输出 RGB 值的小数余数（即提高像素的机会）但是我总是得到一个零值）我认为这是因为颜色被量化到 0-255 比例在他们到达着色器之前，但我不知道为什么会这样，因为我使用的是 A32B32G32R32f 格式，它应该能够存储大量有关颜色的信息。这是我非常简单的着色器代码。如果这很重要，我正在使用 SlimDX (DX9)。

sampler2D Tex0 : register(s0);
float4 DitherByChance(float2 coords : TEXCOORD0) : COLOR
{
    float4 newColor = float4(0, 0, 0, 0);   // The pixel color to return
    double4 oldColor = tex2D(Tex0, coords);
    double scale = 0.0039215686274509803921568627451;  // 1 / 255

    double rPercentChance = frac(oldColor.r / scale);   //Chance to round red channel up
    double gPercentChance = frac(oldColor.g / scale);   //Chance to round green channel up
    double bPercentChance = frac(oldColor.b / scale);   //Chance to round blue channel up

    newColor.r = rPercentChance;
    newColor.g = gPercentChance;
    newColor.b = bPercentChance;

    newColor.a = 1;

    return newColor;
}

technique DitherViaChance  
{  
    pass Pass1  
    {  
        PixelShader = compile ps_2_0 DitherByChance();      
    }  
}

如果重要的话，这是我的 slimDX 代码：

Public Class TextStimulusDisplay
    Inherits BaseStimulusDisplay

    Protected ditherByChanceEffect As PixelShader
    Protected psByteCode As ShaderBytecode
    Protected gStream As DataStream
    Protected ditherBC As Effect

    Protected tex As Texture
    Protected spriteRender As Sprite

    Public displaySettings As DisplaySettings
    Public charText As Texture
    Public randomText As Texture

    Protected rando As Random

    Public Sub New(ByVal displaysettings As DisplaySettings, Optional ByVal WindowedMode As Boolean = False)
        MyBase.New(New Size(displaysettings.xResolution, displaysettings.yResolution), WindowedMode)
        Me.displaySettings = displaysettings
    End Sub

    Public Overrides Sub CreateDeviceResources()
        MyBase.CreateDeviceResources()
        ditherBC = Effect.FromFile(device, Application.StartupPath & "\effects\DitherByChance.fx", ShaderFlags.Debug)
        rando = New Random()

        randomText = New Texture(device, 100, 100, 1, Usage.Dynamic, Format.A32B32G32R32F, Pool.Default)
        Dim data(80000) As Byte
        rando.NextBytes(data)
        Dim dataBox As DataRectangle = randomText.GetSurfaceLevel(0).LockRectangle(LockFlags.None)
        dataBox.Data.Seek(0, IO.SeekOrigin.Begin)
        dataBox.Data.Write(data, 0, data.Length)
        dataBox.Data.Close()
        randomText.GetSurfaceLevel(0).UnlockRectangle()

        device.SetTexture(1, randomText)

        'psByteCode = ShaderBytecode.CompileFromFile(Application.StartupPath & "\effects\DitherByChance.fx", "DitherByChance", "ps_2_0", ShaderFlags.None)
        'ditherByChanceEffect = New PixelShader(device, psByteCode)
        'device.PixelShader = ditherByChanceEffect
        spriteRender = New Sprite(device)
        spriteRender.Transform = Matrix.Identity
        tex = createCharacterTexture()

    End Sub

    Public Overrides Sub ReleaseDeviceResources()
        MyBase.ReleaseDeviceResources()
    End Sub

    Public Overrides Sub RenderScene()
        'ditherBC.Technique = ditherBC.GetTechnique("DitherViaChance")

        Me.device.BeginScene()
        spriteRender.Begin(SpriteFlags.None)
        ditherBC.Begin()
        ditherBC.BeginPass(0)
        spriteRender.Draw(tex, New Rectangle(0, 0, 50, 50), New Color4(1, 1, 1))
        'spriteRender.Draw(randomText, New Rectangle(0, 0, 1000, 1000), New Color4(1, 1, 1))
        spriteRender.End()
        ditherBC.EndPass()
        ditherBC.End()
        Me.device.EndScene()
    End Sub

    Public Function createCharacterTexture() As Texture
        Dim RtsHelper As RenderToSurface = New RenderToSurface(device, 100, 100, Format.A32B32G32R32F)
        Dim texture As Texture = New Texture(device, 100, 100, 1, Usage.RenderTarget, Format.A32B32G32R32F, Pool.Default)

        Dim sloanFont As Font = New Font(device, 98, 98, FontWeight.Normal, 1, False, CharacterSet.Default, Precision.Default,
                                         FontQuality.ClearTypeNatural, PitchAndFamily.Default, "Sloan")


        RtsHelper.BeginScene(texture.GetSurfaceLevel(0), New Viewport(0, 0, 100, 100))



        sloanFont.DrawString(Nothing, "A", 1, 1, New SlimDX.Color4())
        RtsHelper.EndScene(Filter.None)

        Font.Dispose()
        RtsHelper.Dispose()

        Return texture
    End Function
End Class
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