HLSL 修改像素着色器中的深度

Question

我需要渲染一个从外面得到的图像(有深度(。我可以构造两个纹理并将它们毫无问题地传递到着色器中(我可以验证像素着色器中采样的值是否正确(。

以下是我的 HLSL 的样子：

// image texture
Texture2D m_TextureColor : register(t0);
// depth texture with values [0..1]
Texture2D<float> m_TextureDepth : register(t1);
// sampler to forbid linear filtering since we're dealing with pixels
SamplerState m_TextureSampler { Filter = MIN_MAG_MIP_POINT; };
struct VS_IN
{
float4 position : POSITION;
float2 texcoord : TEXCOORD;
};
struct VS_OUT
{
float4 position : SV_POSITION;
float2 texcoord : TEXCOORD0;
};
struct PS_OUT
{
float4 color : COLOR0;
float depth : DEPTH0;
};
VS_OUT VS(VS_IN input)
{
VS_OUT output = (VS_OUT)0;
output.position = input.position;
output.texcoord = input.texcoord;
return output;
}
PS_OUT PS(VS_OUT input) : SV_Target
{
PS_OUT output = (PS_OUT)0;
output.color = m_TextureColor.SampleLevel(m_TextureSampler, input.texcoord, 0);
// I want to modify depth of the pixel,
// but it looks like it has no effect on depth no matter what I set here
output.depth = m_TextureDepth.SampleLevel(m_TextureSampler, input.texcoord, 0);
return output;
}

我从那些(带有PrimitiveTopology.TriangleStrip(构造顶点缓冲区，其中第一个参数Vector4是位置，第二个参数Vector2是纹理坐标：

new[]
{
new Vertex(new Vector4(-1, -1, 0.5f, 1), new Vector2(0, 1)),
new Vertex(new Vector4(-1, 1, 0.5f, 1), new Vector2(0, 0)),
new Vertex(new Vector4(1, -1, 0.5f, 1), new Vector2(1, 1)),
new Vertex(new Vector4(1, 1, 0.5f, 1), new Vector2(1, 0)),
}

一切正常：我看到了我的图像，我可以从深度纹理中采样深度并从中构建一些视觉效果(这就是我验证的方式 我采样的深度值是正确的(。但是，我不知道如何修改像素的深度，以便在进行深度测试时正确食用它。因为目前这一切都取决于我设置为顶点位置的 z 值类型。

这就是我设置DirectX11的方式(我正在使用SharpDX和C#(：

var swapChainDescription = new SwapChainDescription
{
BufferCount = 1,
ModeDescription = new ModeDescription(bufferSize.Width, bufferSize.Height, new Rational(60, 1), Format.R8G8B8A8_UNorm),
IsWindowed = true,
OutputHandle = HostHandle,
SampleDescription = new SampleDescription(1, 0),
SwapEffect = SwapEffect.Discard,
Usage = Usage.RenderTargetOutput,
};
var swapChainFlags = DeviceCreationFlags.None | DeviceCreationFlags.BgraSupport;
SharpDX.Direct3D11.Device.CreateWithSwapChain(DriverType.Hardware, swapChainFlags, swapChainDescription, out var device, out var swapchain);

设置后台缓冲区和深度/模具缓冲区：

// color buffer
using (var textureColor = SwapChain.GetBackBuffer<Texture2D>(0))
{
TextureColorResourceView = new RenderTargetView(Device, textureColor);
}
// depth buffer
using (var textureDepth = new Texture2D(Device, new Texture2DDescription
{
Format = Format.D32_Float,
ArraySize = 1,
MipLevels = 1,
Width = BufferSize.Width,
Height = BufferSize.Height,
SampleDescription = new SampleDescription(1, 0),
Usage = ResourceUsage.Default,
BindFlags = BindFlags.DepthStencil,
CpuAccessFlags = CpuAccessFlags.None,
OptionFlags = ResourceOptionFlags.None
}))
{
TextureDepthResourceView = new DepthStencilView(Device, textureDepth);
}
DeviceContext.OutputMerger.SetTargets(TextureDepthResourceView, TextureColorResourceView);

准备深度模板状态：

var description = DepthStencilStateDescription.Default();
description.DepthComparison = Comparison.LessEqual;
description.IsDepthEnabled = true;
description.DepthWriteMask = DepthWriteMask.All;
DepthState = new DepthStencilState(Device, description);

并使用它：

DeviceContext.OutputMerger.SetDepthStencilState(DepthState);

这是我如何构建发送到着色器的颜色/深度纹理：

public static (ShaderResourceView resource, Texture2D texture) CreateTextureDynamic(this Device device, System.Drawing.Size size, Format format)
{
var textureDesc = new Texture2DDescription
{
MipLevels = 1,
Format = format,
Width = size.Width,
Height = size.Height,
ArraySize = 1,
BindFlags = BindFlags.ShaderResource,
Usage = ResourceUsage.Dynamic,
SampleDescription = new SampleDescription(1, 0),
CpuAccessFlags = CpuAccessFlags.Write,
};
var texture = new Texture2D(device, textureDesc);
return (new ShaderResourceView(device, texture), texture);
}

另外，因为我需要经常更新它们：

public static void UpdateResource(this Texture2D texture, int[] buffer, System.Drawing.Size size)
{
var dataBox = texture.Device.ImmediateContext.MapSubresource(texture, 0, MapMode.WriteDiscard, MapFlags.None, out var dataStream);
Parallel.For(0, size.Height, rowIndex => Marshal.Copy(buffer, size.Width * rowIndex, dataBox.DataPointer + dataBox.RowPitch * rowIndex, size.Width));
dataStream.Dispose();
texture.Device.ImmediateContext.UnmapSubresource(texture, 0);
}
public static void UpdateResource(this Texture2D texture, float[] buffer, System.Drawing.Size size)
{
var dataBox = texture.Device.ImmediateContext.MapSubresource(texture, 0, MapMode.WriteDiscard, MapFlags.None, out var dataStream);
Parallel.For(0, size.Height, rowIndex => Marshal.Copy(buffer, size.Width * rowIndex, dataBox.DataPointer + dataBox.RowPitch * rowIndex, size.Width));
dataStream.Dispose();
texture.Device.ImmediateContext.UnmapSubresource(texture, 0);
}

我也用谷歌搜索了很多关于这个的信息，找到了类似的帖子，比如： https://www.gamedev.net/forums/topic/573961-how-to-set-depth-value-in-pixel-shader/然而，我这边无法解决它。

提前感谢！

Answer 1

若要写入深度缓冲区，需要以SV_Depth系统值语义为目标。因此，像素着色器输出结构看起来更像以下内容：

struct PS_OUT
{
float4 color : SV_Target;
float depth : SV_Depth;
};

着色器不会像您的示例中那样指定SV_Target(SV_输出在结构中定义(。所以它看起来像：

PS_OUT PS(VS_OUT input)
{
PS_OUT output = (PS_OUT)0;
output.color = m_TextureColor.SampleLevel(m_TextureSampler, input.texcoord, 0);
// Now that output.depth is defined with SV_Depth, and you have depth-write enabled,
// this should write to the depth buffer.
output.depth = m_TextureDepth.SampleLevel(m_TextureSampler, input.texcoord, 0);
return output;
}

请注意，显式写入深度(特别是在 AMD 硬件上(可能会产生一些性能损失，因为这会强制绕过其早期深度硬件优化。将来使用该深度缓冲区的所有绘制调用都将禁用早期 Z 优化，因此通常最好尽可能晚地执行深度写入操作。