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DX 几何着色器

时间：2023-02-28 21:57:20浏览次数：31  
标签：std 1.0 DX 几何 indices 顶点 geo 着色器

前言

​ 本篇为个人学习笔记，主要展示什么是几何着色器，及为什么需要它，如何使用几何着色器，以及用公告牌实现森林

什么是几何着色器？

​ 几何着色器是顶点和片段着色器间一个可选的着色器,位于曲面细分和光栅化阶段之间，随着 2006 年底 DirectX 10 的发布被加入到硬件加速图形管线中.几何着色器作为 Shader Model 4.0 的一部分，不能在早期着色模型（<= SM 3.0）中使用

​ 几何着色器以完整的图元(任意类型的图元)作为顶点的数组作为输入,如三角形、线段、点，输出对应的图元。与顶点着色器不同，几何着色器可以创建/销毁图元

​ 几何着色器可以改变输入的图元拓扑结构，但只能输出点、折线和三角形条

​ 几何着色器输出的图元由顶点列表定义，经过几何着色器阶段的处理后，便得到位于齐次裁剪空间中的一系列图元

image-20230119182402532

​

为什么需要几何着色器？

​ 由于几何着色器可以创建/销毁图元，因此根据该特性可以实现许多效果，如将输入的图元扩展为一个或更多其他类型的图元

几何着色器的编写

​ 几何着色器的编写与顶点着色器、片段着色器类似，有几个重点：

  1. 必须先指定几何着色器单次调用输出的顶点数量的最大值。但出于性能考虑，该值需尽可能小.一般来说标量数量1-20最佳,在27-40会下降至峰值性能的50%，标量个数等于顶点数量的最大值*顶点结构体中标量个数的乘积,如一个顶点结构体定义"float3 pos : POSITION"和"float2 tex : TEXCOORD"，那么该结构体包含五个标量

  2. 几何着色器的输入顶点类型为顶点着色器输出的顶点类型，该输入参数必须是一个包含特定图元的顶点数组——点为一个顶点，线条为两个顶点，三角形为三个顶点,线及其邻接图元为4个顶点，三角形及其邻接图元为6个顶点,且输入参数必须以图元类型作为前缀,前缀类型如下：

    1. point：输入图元为点
    2. line：输入图元为线列表/线条带
    3. triangle：输入图元为三角形列表/三角形带
    4. lineadj：输入图元为线列表及其邻接图元/线条带及其邻接图元
    5. triangleadj：输入图元为三角形列表及其邻接图元/三角形带及其邻接图元

  3. 几何着色器不会区分输入的图元是列表(list)结构还是带状(strip)结构。如，若绘制的图元为三角形带，几何着色器仍把三角形带看作多个三角形并对其拆分单独进行处理——三角形三个顶点.但是绘制strip结构会产生额外开销，因为几何着色器会多次处理共用的顶点(毕竟这里没有索引)

  4. 输出是一种流(stream)类型，且输入必须标有inout修饰符。stream是模板类型，存有一系列顶点，它们定义了几何着色器输出的几何图形,这些顶点会构成图元

    • stream类型有如下三种

      1. PointStream<OutputVertexType> ：一系列顶点定义的点列表
      2. LineStream<OutputVertexType>：一系列顶点定义的线条带
      3. TriangleStream<OutputVertexType>：一系列顶点定义的三角形带

    • 对于线条和三角形来说，几何着色器输出的对应图元默认为线条带和三角形带，若想输出线条列表和三角形列表需借助函数RestartStrip()

      void StreamOutputObject<OutputVertexType>::RestartStrip();

    • 向流列表中添加顶点：Append()

      void StreamOutputObject<OutputVertexType>::Append(OutputVertexType v);

以下为它的模板：

[maxvertexcount(N)]	//单次调用所输出的顶点数量的最大值
void ShaderName (PrimitiveType InputVertexType InputName[NumElements], inout StreamOutputObject<OutputVertexType>OutputName)
{
	// Geometry shader body…
}

​ 来看一些示例：

  • GS最多输出4个顶点，输入图元为一根线条，输出为一个三角形带

    [maxvertexcount(4)]
void GS(line VertexOut gin[2], inout TriangleStream<GeoOut> triStream)
{
    //...
}

  • GS最多输出32个顶点，输入图元为一个三角形，输出为一个三角形带

    [maxvertexcount(32)]
void GS(triangle VertexOut gin[3], inout TriangleStream<GeoOut> triStream)
{
    //...
}

  • GS最多输出4个顶点，输入图元为一个点，输出为一个三角形带

    [maxvertexcount(4)]
void GS(point VertexOut gin[1], inout TriangleStream<GeoOut> triStream)
{
    //...
}

  • Append()和RestartStrip()的使用方法，该实例将输入的三角形细分，并输出细分后的4个三角形
    image-20230227203916770

    struct VertexOut
{
    float3 PosL : POSITION;
    float3 NormalL : NORMAL;
	float2 Tex : TEXCOORD;
}

struct GeoOut
{
    float4 PosH : SV_POSITION;
	float3 PosW : POSITION;
	float3 NormalW : NORMAL;
	float2 Tex : TEXCOORD;
    float FogLerp : FOG;
}

//细分
void Subdivide(VertexOut inVerts[3], out VertexOut  outVerts[6])
{
    // 		  1
	// 		  *
	// 	     / \
	// 	    /   \
	//     m0*–—*m1
	//    / \    / \
	//   /   \  /   \
	//  *–-----*--–--—*
	//  0      m2      2
    VertexOut m[3];
    
    //计算三角形每条边的中点
	m[0].PosL = 0.5f*(inVerts[0].PosL+inVerts[1].PosL);
	m[1].PosL = 0.5f*(inVerts[1].PosL+inVerts[2].PosL);
	m[2].PosL = 0.5f*(inVerts[2].PosL+inVerts[0].PosL);

    //规范化
    m[0].PosL = normalize(m[0].PosL);
	m[1].PosL = normalize(m[1].PosL);
	m[2].PosL = normalize(m[2].PosL);
    
    //求法线
    m[0].NormalL = m[0].PosL;
	m[1].NormalL = m[1].PosL;
	m[2].NormalL = m[2].PosL;
    
    //纹理坐标插值
    m[0].Tex = 0.5f*(inVerts[0].Tex+inVerts[1].Tex);
	m[1].Tex = 0.5f*(inVerts[1].Tex+inVerts[2].Tex);
	m[2].Tex = 0.5f*(inVerts[2].Tex+inVerts[0].Tex);

	outVerts[0] = inVerts[0];	
	outVerts[1] = m[0];
	outVerts[2] = m[2];
	outVerts[3] = m[1];
	outVerts[4] = inVerts[2];
	outVerts[5] = inVerts[1];
}

void OutputSubdivision(VertexOut v[6], inout TriangleStream<GeoOut> triStream)
{
    GeoOut gout[6];
    
    [unroll]
	for(int i = 0; i < 6; ++i)
    {
        //顶点变换至世界空间
        gout[i].PosW = mul(float4(v[i].PosL, 1.0f), gWorld).xyz;
		gout[i].NormalW = mul(v[i].NormalL, (float3x3)gWorldInvTranspose);
        
        //顶点变换至齐次裁剪空间
		gout[i].PosH = mul(float4(v[i].PosL, 1.0f), gWorldViewProj);
		gout[i].Tex = v[i].Tex;
        
        //以两个三角形带来绘制细分的三角形
        //三角形带1 ： 底部的三个三角形
        //三角形带2 ： 顶部的一个三角形
        [unroll]
    for(int j = 0; j < 5; ++j)
    {
    	triStream.Append(gout[j]);
    }
    triStream.RestartStrip();
        
    triStream.Append(gout[1]);
    triStream.Append(gout[5]);
    triStream.Append(gout[3]);
}
    
[maxvertexcount(8)]
void GS(triangle VertexOut gin[3], inout TriangleStream<GeoOut>)
{
    VertexOut v[6];
	Subdivide(gin, v);
	OutputSubdivision(v, triStream);
}

几何着色器的编译，绑定至流水线

​ 几何着色器的编译方式和绑定至流水线的方式与VS、PS相同。示例如下：

mShaders["treeSpritePS"] = d3dUtil::CompileShader(L"Shaders\\TreeSprite.hlsl", alphaTestDefines, "PS", "ps_5_0");

D3D12_GRAPHICS_PIPELINE_STATE_DESC treeSpritePsoDesc = opaquePsoDesc;
treeSpritePsoDesc.PS =
{
    reinterpret_cast<BYTE*>(mShaders["treeSpritePS"]->GetBufferPointer()),
    mShaders["treeSpritePS"]->GetBufferSize()
};

用公告板实现森林

  • 何为公告板(Billboarding)？

    公告板是一种用3D物体图片的四边形来替代3D物体的渲染,他会根据观察方向来确定多边形面朝方向,随着观察角度的变化，公告板多边形的方向也会根据需求随之改变

    如下图，所有公告牌都面对着摄像机
    image-20230227222928031

  • 公告板有什么用处？

    与 alpha 纹理 和 动画相结合，可以用公告板技术表示许多不具有平滑实体表面的现象，如烟，火，雾，爆炸效果，云朵等

求四边形公告板的顶点坐标

​ 若给定 世界空间中四边形公告板的中心位置为\(C(C_x, C_y, C_z)\),摄像机位置\(E(E_x, E_y, E_z)\)，公告牌的局部坐标系和世界空间的关系，公告牌在世界空间中的大小，即可求得公告牌的四个顶点坐标
\(w = \frac{(E_x - C_x, 0, E_z - C_z)}{\|E_x - C_x, 0, E_z - C_z \|} \\ v = (0,1,0) \\ u = v \times w\)

v[0] = float4(gin[0].CenterW + halfWidth*right - halfHeight*up, 1.0f);
v[1] = float4(gin[0].CenterW + halfWidth*right + halfHeight*up, 1.0f);
v[2] = float4(gin[0].CenterW - halfWidth*right - halfHeight*up, 1.0f);
v[3] = float4(gin[0].CenterW - halfWidth*right + halfHeight*up, 1.0f);

image-20230227223709931

HLSL示例

​ 由于需要确定公告板的中心点，因此我们需要点图元：
将PSO的PrimitiveTopologyType设为D3D12_PRIMITIVE_TOPOLOGY_TYPE_POINT,ID3D12GraphicsCommandList::IASetPrimitiveTopology设为D3D_PRIMITIVE_TOPOLOGY_POINTLIST。而在几何着色器中，我们需要把这些中心点扩展为公告板的四边形，还需要计算公告板的世界矩阵

  • 顶点结构体

    在顶点结构体中存储公告板的中心点的位置，以及公告板的宽高,如此即可表示其大小
    image-20230228141455637

    struct TreeSpriteVertex
{
    XMFLOAT3 Pos;
    XMFLOAT2 Size;
};

mTreeSpriteInputLayout =
{
    { "POSITION", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 0, D3D12_INPUT_CLASSIFICATION_PER_VERTEX_DATA, 0 },
    { "SIZE", 0, DXGI_FORMAT_R32G32_FLOAT, 0, 12, D3D12_INPUT_CLASSIFICATION_PER_VERTEX_DATA, 0 },
};

  • HLSL实现：以下将展示VS、PS、GS三种着色器是如何搭配使用的

    该例中GS用于把一个点扩展为一个四边形，并让其和y轴对齐来正对相机

    #ifndef NUM_DIR_LIGHTS
    #define NUM_DIR_LIGHTS 3
#endif

#ifndef NUM_POINT_LIGHTS
    #define NUM_POINT_LIGHTS 0
#endif

#ifndef NUM_SPOT_LIGHTS
    #define NUM_SPOT_LIGHTS 0
#endif

// 包含光照所需的结构体和函数
#include "LightingUtil.hlsl"

//纹理数组
Texture2DArray gTreeMapArray : register(t0);

//静态采样器
SamplerState gsamPointWrap        : register(s0);
SamplerState gsamPointClamp       : register(s1);
SamplerState gsamLinearWrap       : register(s2);
SamplerState gsamLinearClamp      : register(s3);
SamplerState gsamAnisotropicWrap  : register(s4);
SamplerState gsamAnisotropicClamp : register(s5);

//与物体相关的常量数据
cbuffer cbPerObject : register(b0)
{
    float4x4 gWorld;
	float4x4 gTexTransform;
};

// 绘制所用的杂项常量数据,每帧更新
cbuffer cbPass : register(b1)
{
    float4x4 gView;
    float4x4 gInvView;
    float4x4 gProj;
    float4x4 gInvProj;
    float4x4 gViewProj;
    float4x4 gInvViewProj;
    float3 gEyePosW;
    float cbPerObjectPad1;
    float2 gRenderTargetSize;
    float2 gInvRenderTargetSize;
    float gNearZ;
    float gFarZ;
    float gTotalTime;
    float gDeltaTime;
    float4 gAmbientLight;

	float4 gFogColor;
	float gFogStart;
	float gFogRange;
	float2 cbPerObjectPad2;

    // Indices [0, NUM_DIR_LIGHTS) are directional lights;
    // indices [NUM_DIR_LIGHTS, NUM_DIR_LIGHTS+NUM_POINT_LIGHTS) are point lights;
    // indices [NUM_DIR_LIGHTS+NUM_POINT_LIGHTS, NUM_DIR_LIGHTS+NUM_POINT_LIGHT+NUM_SPOT_LIGHTS)
    // are spot lights for a maximum of MaxLights per object.
    Light gLights[MaxLights];
};

//材质
cbuffer cbMaterial : register(b2)
{
	float4   gDiffuseAlbedo;
    float3   gFresnelR0;
    float    gRoughness;
	float4x4 gMatTransform;
};

//输入的顶点结构体
struct VertexIn
{
	float3 PosW  : POSITION;
	float2 SizeW : SIZE;
};

//输出的顶点结构体
struct VertexOut
{
	float3 CenterW : POSITION;
	float2 SizeW   : SIZE;
};

//GS的输出结构体
struct GeoOut
{
	float4 PosH    : SV_POSITION;
    float3 PosW    : POSITION;
    float3 NormalW : NORMAL;
    float2 TexC    : TEXCOORD;
    uint   PrimID  : SV_PrimitiveID;
};

VertexOut VS(VertexIn vin)
{
	VertexOut vout;

	vout.CenterW = vin.PosW;
	vout.SizeW   = vin.SizeW;

	return vout;
}

 // 因为需要将一个点扩展为一个四边形，所以每次调用GS最多输出四个顶点
[maxvertexcount(4)]
void GS(point VertexOut gin[1], 
        uint primID : SV_PrimitiveID, 
        inout TriangleStream<GeoOut> triStream)
{	
	//计算公告板的局部坐标系和世界空间的相对关系，使得公告板和y轴对齐且面向相机
	float3 up = float3(0.0f, 1.0f, 0.0f);
	float3 look = gEyePosW - gin[0].CenterW;
	look.y = 0.0f; // 使公告板立于xz平面
	look = normalize(look);
	float3 right = cross(up, look);

	// 计算世界空间中四边形的顶点
	float halfWidth  = 0.5f*gin[0].SizeW.x;
	float halfHeight = 0.5f*gin[0].SizeW.y;
	
	float4 v[4];
	v[0] = float4(gin[0].CenterW + halfWidth*right - halfHeight*up, 1.0f);
	v[1] = float4(gin[0].CenterW + halfWidth*right + halfHeight*up, 1.0f);
	v[2] = float4(gin[0].CenterW - halfWidth*right - halfHeight*up, 1.0f);
	v[3] = float4(gin[0].CenterW - halfWidth*right + halfHeight*up, 1.0f);

	//将四边形的顶点变换到世界空间，将其以三角形带的形式输出
	float2 texC[4] = 
	{
		float2(0.0f, 1.0f),
		float2(0.0f, 0.0f),
		float2(1.0f, 1.0f),
		float2(1.0f, 0.0f)
	};
	
	GeoOut gout;
	[unroll]
	for(int i = 0; i < 4; ++i)
	{
		gout.PosH     = mul(v[i], gViewProj);
		gout.PosW     = v[i].xyz;
		gout.NormalW  = look;
		gout.TexC     = texC[i];
		gout.PrimID   = primID;
		
		triStream.Append(gout);
	}
}

float4 PS(GeoOut pin) : SV_Target
{
	float3 uvw = float3(pin.TexC, pin.PrimID%3);
    float4 diffuseAlbedo = gTreeMapArray.Sample(gsamAnisotropicWrap, uvw) * gDiffuseAlbedo;
	
#ifdef ALPHA_TEST
	// Discard pixel if texture alpha < 0.1.  We do this test as soon 
	// as possible in the shader so that we can potentially exit the
	// shader early, thereby skipping the rest of the shader code.
	clip(diffuseAlbedo.a - 0.1f);
#endif

    // Interpolating normal can unnormalize it, so renormalize it.
    pin.NormalW = normalize(pin.NormalW);

    // 光线经物体表面一点反射到相机方向的向量
	float3 toEyeW = gEyePosW - pin.PosW;
	float distToEye = length(toEyeW);
	toEyeW /= distToEye; // normalize

    // Light terms.
    float4 ambient = gAmbientLight*diffuseAlbedo;

    const float shininess = 1.0f - gRoughness;
    Material mat = { diffuseAlbedo, gFresnelR0, shininess };
    float3 shadowFactor = 1.0f;
    float4 directLight = ComputeLighting(gLights, mat, pin.PosW,
        pin.NormalW, toEyeW, shadowFactor);

    float4 litColor = ambient + directLight;

#ifdef FOG
	float fogAmount = saturate((distToEye - gFogStart) / gFogRange);
	litColor = lerp(litColor, gFogColor, fogAmount);
#endif

    // Common convention to take alpha from diffuse albedo.
    litColor.a = diffuseAlbedo.a;

    return litColor;
}

    可以看到其中有两个未见过的声明，它们分别意为语义和纹理数组：

    uint primID : SV_PrimitiveID
Texture2DArray gTreeMapArray : register(t0);

    1. SV_PrimitiveID语义

      1. 在VS中使用SV_PrimitiveID语义

        在输入装配器阶段会自动为每个图元生成图元ID，假设绘制n个图元，第一个图元标记为0，第二个标记为1······最后一个为n-1

        VertexOut VS(VertexIn vin, uint vertID : SV_VertexID)

      2. 在GS中使用SV_PrimitiveID语义

        仅用于将图元ID写入输出的顶点

        [maxvertexcount(4)]
void GS(point VertexOut gin[1], 
        uint primID : SV_PrimitiveID, 
        inout TriangleStream<GeoOut> triStream)

      3. 在PS中SV_PrimitiveID语义

        PS将图元ID用作纹理数组的索引

        float4 PS(VertexOut pin, uint primID : SV_PrimitiveID : SV_Target)

    2. 纹理数组：存放纹理的数组,用接口ID3D12Resource表示

      1. 创建方式

        Texture2DArray gTreeMapArray : register(t0);

        那为什么不使用C样式的数组初始化方式呢？

        Texture2D TexArray[4];

        在着色器5.1模型中可以这样写，但在这之前的版本不可以。而且，该实现方式可能会产生额外开销

      2. 指定纹理数组存储元素个数：设置DepthOrArraySize属性来指定纹理数组存储元素个数。若是3D纹理，该项指定为深度值

      3. 对纹理数组采样：使用纹理数组需要三个坐标，前两个为2D纹理坐标，第三个为该纹理的索引

        float3 uvw = float3(pin.TexC, pin.PrimID%3);
float4 diffuseAlbedo = gTreeMapArray.Sample(gsamAnisotropicWrap, uvw) * gDiffuseAlbedo;

      4. 好处

        1. 在一次绘制调用中，可以画出不同纹理的图元。一般而言，必须用不同纹理对每个有着独立渲染项的网格进行处理,但使用纹理数组，便只需调用一次

          SetTextureArray();
DrawPrimitivesWithTextureArray();

      5. 加载纹理数组

        微软公司提供了加载纹理数组的工具texassemble

        • 合并多个.dds图像为一个纹理数组treeArray.dds

          texassemble -array -o treeArray.dds t0.dds t1.dds t2.dds t3.dds

        • 需要注意的是使用texassemble构建纹理数组时，输入的多个图像只能各有一种mipmap层级，创建后可以通过texconv工具生成多种mipmap层级,并改变纹理格式

          texconv -m 10 -f BC3_UNORM treeArray.dds

      6. 纹理子资源(subresource)

        下图展示了一个拥有多个纹理的纹理数组，其中每个纹理都有自己的mipmap链。我们用数组切片(array slice)表示纹理数组中的某个纹理及其mipmap链，用切片(mip slice)表示纹理数组中某一层级的所有mipmap，而子资源是指纹理数组中某纹理的单个mipmap层级,而子资源也是以线性索引进行标记的
        image-20230228164227446
        image-20230228165308103

        D3D也提供了相应的函数来计算子资源的线性索引，给定mip切片索引、数组切片索引、平面切片(对某些YUV平面格式的分量以索引方式进行单独提取，不需要则设为0)索引、mipmap层级、纹理数组大小即可

      最后再结合上篇所讲的AlphaToCoverage技术解决森林边缘失真的问题实现该示例

大致流程

  1. 加载纹理

    auto grassTex = std::make_unique<Texture>();
grassTex->Name = "grassTex";
grassTex->Filename = L"../../Textures/grass.dds";
ThrowIfFailed(DirectX::CreateDDSTextureFromFile12(md3dDevice.Get(),
		mCommandList.Get(), grassTex->Filename.c_str(),
		grassTex->Resource, grassTex->UploadHeap));

auto waterTex = std::make_unique<Texture>();
waterTex->Name = "waterTex";
waterTex->Filename = L"../../Textures/water1.dds";
ThrowIfFailed(DirectX::CreateDDSTextureFromFile12(md3dDevice.Get(),
		mCommandList.Get(), waterTex->Filename.c_str(),
		waterTex->Resource, waterTex->UploadHeap));

auto fenceTex = std::make_unique<Texture>();
fenceTex->Name = "fenceTex";
fenceTex->Filename = L"../../Textures/WireFence.dds";
ThrowIfFailed(DirectX::CreateDDSTextureFromFile12(md3dDevice.Get(),
		mCommandList.Get(), fenceTex->Filename.c_str(),
		fenceTex->Resource, fenceTex->UploadHeap));

auto treeArrayTex = std::make_unique<Texture>();
treeArrayTex->Name = "treeArrayTex";
treeArrayTex->Filename = L"../../Textures/treeArray2.dds";
ThrowIfFailed(DirectX::CreateDDSTextureFromFile12(md3dDevice.Get(),
		mCommandList.Get(), treeArrayTex->Filename.c_str(),
		treeArrayTex->Resource, treeArrayTex->UploadHeap));

mTextures[grassTex->Name] = std::move(grassTex);
mTextures[waterTex->Name] = std::move(waterTex);
mTextures[fenceTex->Name] = std::move(fenceTex);
mTextures[treeArrayTex->Name] = std::move(treeArrayTex);

  2. 创建根签名

    //四个根参数：一个描述符表，三个描述符
CD3DX12_DESCRIPTOR_RANGE texTable;
texTable.Init(D3D12_DESCRIPTOR_RANGE_TYPE_SRV, 1, 0);

// Root parameter can be a table, root descriptor or root constants.
CD3DX12_ROOT_PARAMETER slotRootParameter[4];

// Perfomance TIP: Order from most frequent to least frequent.
slotRootParameter[0].InitAsDescriptorTable(1, &texTable, D3D12_SHADER_VISIBILITY_PIXEL);
slotRootParameter[1].InitAsConstantBufferView(0);
slotRootParameter[2].InitAsConstantBufferView(1);
slotRootParameter[3].InitAsConstantBufferView(2);

auto staticSamplers = GetStaticSamplers();

// A root signature is an array of root parameters.
CD3DX12_ROOT_SIGNATURE_DESC rootSigDesc(4, slotRootParameter,
                                        (UINT)staticSamplers.size(), staticSamplers.data(),
                                        D3D12_ROOT_SIGNATURE_FLAG_ALLOW_INPUT_ASSEMBLER_INPUT_LAYOUT);

// create a root signature with a single slot which points to a descriptor range consisting of a single constant buffer
ComPtr<ID3DBlob> serializedRootSig = nullptr;
ComPtr<ID3DBlob> errorBlob = nullptr;
HRESULT hr = D3D12SerializeRootSignature(&rootSigDesc, D3D_ROOT_SIGNATURE_VERSION_1,
                                         serializedRootSig.GetAddressOf(), errorBlob.GetAddressOf());

if(errorBlob != nullptr)
{
    ::OutputDebugStringA((char*)errorBlob->GetBufferPointer());
}
ThrowIfFailed(hr);

ThrowIfFailed(md3dDevice->CreateRootSignature(
    0,
    serializedRootSig->GetBufferPointer(),
    serializedRootSig->GetBufferSize(),
    IID_PPV_ARGS(mRootSignature.GetAddressOf())));

  3. 创建描述符堆

    //创建SRV描述符堆，存储四个不同的纹理资源的描述符
D3D12_DESCRIPTOR_HEAP_DESC srvHeapDesc = {};
srvHeapDesc.NumDescriptors = 4;
srvHeapDesc.Type = D3D12_DESCRIPTOR_HEAP_TYPE_CBV_SRV_UAV;
srvHeapDesc.Flags = D3D12_DESCRIPTOR_HEAP_FLAG_SHADER_VISIBLE;
ThrowIfFailed(md3dDevice->CreateDescriptorHeap(&srvHeapDesc, IID_PPV_ARGS(&mSrvDescriptorHeap)));

//
// Fill out the heap with actual descriptors.
//
CD3DX12_CPU_DESCRIPTOR_HANDLE hDescriptor(mSrvDescriptorHeap->GetCPUDescriptorHandleForHeapStart());

auto grassTex = mTextures["grassTex"]->Resource;
auto waterTex = mTextures["waterTex"]->Resource;
auto fenceTex = mTextures["fenceTex"]->Resource;
auto treeArrayTex = mTextures["treeArrayTex"]->Resource;

D3D12_SHADER_RESOURCE_VIEW_DESC srvDesc = {};
srvDesc.Shader4ComponentMapping = D3D12_DEFAULT_SHADER_4_COMPONENT_MAPPING;
srvDesc.Format = grassTex->GetDesc().Format;
srvDesc.ViewDimension = D3D12_SRV_DIMENSION_TEXTURE2D;
srvDesc.Texture2D.MostDetailedMip = 0;
srvDesc.Texture2D.MipLevels = -1;
md3dDevice->CreateShaderResourceView(grassTex.Get(), &srvDesc, hDescriptor);

// next descriptor
hDescriptor.Offset(1, mCbvSrvDescriptorSize);

srvDesc.Format = waterTex->GetDesc().Format;
md3dDevice->CreateShaderResourceView(waterTex.Get(), &srvDesc, hDescriptor);

// next descriptor
hDescriptor.Offset(1, mCbvSrvDescriptorSize);

srvDesc.Format = fenceTex->GetDesc().Format;
md3dDevice->CreateShaderResourceView(fenceTex.Get(), &srvDesc, hDescriptor);

// next descriptor
hDescriptor.Offset(1, mCbvSrvDescriptorSize);

auto desc = treeArrayTex->GetDesc();
srvDesc.ViewDimension = D3D12_SRV_DIMENSION_TEXTURE2DARRAY;
srvDesc.Format = treeArrayTex->GetDesc().Format;
srvDesc.Texture2DArray.MostDetailedMip = 0;
srvDesc.Texture2DArray.MipLevels = -1;
srvDesc.Texture2DArray.FirstArraySlice = 0;
srvDesc.Texture2DArray.ArraySize = treeArrayTex->GetDesc().DepthOrArraySize;
md3dDevice->CreateShaderResourceView(treeArrayTex.Get(), &srvDesc, hDescriptor);

  4. 创建着色器和输入布局

    //着色器使用的宏，是否实现雾和alpha test
const D3D_SHADER_MACRO defines[] =
{
    "FOG", "1",
    NULL, NULL
};

const D3D_SHADER_MACRO alphaTestDefines[] =
{
    "FOG", "1",
    "ALPHA_TEST", "1",
    NULL, NULL
};

mShaders["standardVS"] = d3dUtil::CompileShader(L"Shaders\\Default.hlsl", nullptr, "VS", "vs_5_0");
mShaders["opaquePS"] = d3dUtil::CompileShader(L"Shaders\\Default.hlsl", defines, "PS", "ps_5_0");	//开启雾效
mShaders["alphaTestedPS"] = d3dUtil::CompileShader(L"Shaders\\Default.hlsl", alphaTestDefines, "PS", "ps_5_0");	//开启雾效，alpha test

mShaders["treeSpriteVS"] = d3dUtil::CompileShader(L"Shaders\\TreeSprite.hlsl", nullptr, "VS", "vs_5_0");
mShaders["treeSpriteGS"] = d3dUtil::CompileShader(L"Shaders\\TreeSprite.hlsl", nullptr, "GS", "gs_5_0");
mShaders["treeSpritePS"] = d3dUtil::CompileShader(L"Shaders\\TreeSprite.hlsl", alphaTestDefines, "PS", "ps_5_0");

mStdInputLayout =
{
    { "POSITION", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 0, D3D12_INPUT_CLASSIFICATION_PER_VERTEX_DATA, 0 },
    { "NORMAL", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 12, D3D12_INPUT_CLASSIFICATION_PER_VERTEX_DATA, 0 },
    { "TEXCOORD", 0, DXGI_FORMAT_R32G32_FLOAT, 0, 24, D3D12_INPUT_CLASSIFICATION_PER_VERTEX_DATA, 0 },
};

//用于实现公告板的顶点结构体布局
mTreeSpriteInputLayout =
{
    { "POSITION", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 0, D3D12_INPUT_CLASSIFICATION_PER_VERTEX_DATA, 0 },
    { "SIZE", 0, DXGI_FORMAT_R32G32_FLOAT, 0, 12, D3D12_INPUT_CLASSIFICATION_PER_VERTEX_DATA, 0 },
};

  5. 生成陆地、海洋、立方体

    //生成陆地
GeometryGenerator geoGen;
GeometryGenerator::MeshData grid = geoGen.CreateGrid(160.0f, 160.0f, 50, 50);

// 获取所需要的顶点，并利用高度函数计算每个顶点的高度值
// 顶点的颜色基于高度而定

std::vector<Vertex> vertices(grid.Vertices.size());
for(size_t i = 0; i < grid.Vertices.size(); ++i)
{
    auto& p = grid.Vertices[i].Position;
    vertices[i].Pos = p;
    vertices[i].Pos.y = GetHillsHeight(p.x, p.z);
    vertices[i].Normal = GetHillsNormal(p.x, p.z);
    vertices[i].TexC = grid.Vertices[i].TexC;
}

const UINT vbByteSize = (UINT)vertices.size() * sizeof(Vertex);

std::vector<std::uint16_t> indices = grid.GetIndices16();
const UINT ibByteSize = (UINT)indices.size() * sizeof(std::uint16_t);

auto geo = std::make_unique<MeshGeometry>();
geo->Name = "landGeo";

ThrowIfFailed(D3DCreateBlob(vbByteSize, &geo->VertexBufferCPU));
CopyMemory(geo->VertexBufferCPU->GetBufferPointer(), vertices.data(), vbByteSize);

ThrowIfFailed(D3DCreateBlob(ibByteSize, &geo->IndexBufferCPU));
CopyMemory(geo->IndexBufferCPU->GetBufferPointer(), indices.data(), ibByteSize);

geo->VertexBufferGPU = d3dUtil::CreateDefaultBuffer(md3dDevice.Get(),
                                                    mCommandList.Get(), vertices.data(), vbByteSize, geo->VertexBufferUploader);

geo->IndexBufferGPU = d3dUtil::CreateDefaultBuffer(md3dDevice.Get(),
                                                   mCommandList.Get(), indices.data(), ibByteSize, geo->IndexBufferUploader);

geo->VertexByteStride = sizeof(Vertex);
geo->VertexBufferByteSize = vbByteSize;
geo->IndexFormat = DXGI_FORMAT_R16_UINT;
geo->IndexBufferByteSize = ibByteSize;

SubmeshGeometry submesh;
submesh.IndexCount = (UINT)indices.size();
submesh.StartIndexLocation = 0;
submesh.BaseVertexLocation = 0;

geo->DrawArgs["grid"] = submesh;

mGeometries["landGeo"] = std::move(geo);

//生成海洋
std::vector<std::uint16_t> indices(3 * mWaves->TriangleCount()); // 3 indices per face
assert(mWaves->VertexCount() < 0x0000ffff);

// Iterate over each quad.
int m = mWaves->RowCount();
int n = mWaves->ColumnCount();
int k = 0;
for(int i = 0; i < m - 1; ++i)
{
    for(int j = 0; j < n - 1; ++j)
    {
        indices[k] = i*n + j;
        indices[k + 1] = i*n + j + 1;
        indices[k + 2] = (i + 1)*n + j;

        indices[k + 3] = (i + 1)*n + j;
        indices[k + 4] = i*n + j + 1;
        indices[k + 5] = (i + 1)*n + j + 1;

        k += 6; // next quad
    }
}

UINT vbByteSize = mWaves->VertexCount()*sizeof(Vertex);
UINT ibByteSize = (UINT)indices.size()*sizeof(std::uint16_t);

auto geo = std::make_unique<MeshGeometry>();
geo->Name = "waterGeo";

// Set dynamically.
geo->VertexBufferCPU = nullptr;
geo->VertexBufferGPU = nullptr;

ThrowIfFailed(D3DCreateBlob(ibByteSize, &geo->IndexBufferCPU));
CopyMemory(geo->IndexBufferCPU->GetBufferPointer(), indices.data(), ibByteSize);

geo->IndexBufferGPU = d3dUtil::CreateDefaultBuffer(md3dDevice.Get(),
                                                   mCommandList.Get(), indices.data(), ibByteSize, geo->IndexBufferUploader);

geo->VertexByteStride = sizeof(Vertex);
geo->VertexBufferByteSize = vbByteSize;
geo->IndexFormat = DXGI_FORMAT_R16_UINT;
geo->IndexBufferByteSize = ibByteSize;

SubmeshGeometry submesh;
submesh.IndexCount = (UINT)indices.size();
submesh.StartIndexLocation = 0;
submesh.BaseVertexLocation = 0;

geo->DrawArgs["grid"] = submesh;

mGeometries["waterGeo"] = std::move(geo);

//生成立方体
GeometryGenerator geoGen;
GeometryGenerator::MeshData box = geoGen.CreateBox(8.0f, 8.0f, 8.0f, 3);

std::vector<Vertex> vertices(box.Vertices.size());
for (size_t i = 0; i < box.Vertices.size(); ++i)
{
    auto& p = box.Vertices[i].Position;
    vertices[i].Pos = p;
    vertices[i].Normal = box.Vertices[i].Normal;
    vertices[i].TexC = box.Vertices[i].TexC;
}

const UINT vbByteSize = (UINT)vertices.size() * sizeof(Vertex);

std::vector<std::uint16_t> indices = box.GetIndices16();
const UINT ibByteSize = (UINT)indices.size() * sizeof(std::uint16_t);

auto geo = std::make_unique<MeshGeometry>();
geo->Name = "boxGeo";

ThrowIfFailed(D3DCreateBlob(vbByteSize, &geo->VertexBufferCPU));
CopyMemory(geo->VertexBufferCPU->GetBufferPointer(), vertices.data(), vbByteSize);

ThrowIfFailed(D3DCreateBlob(ibByteSize, &geo->IndexBufferCPU));
CopyMemory(geo->IndexBufferCPU->GetBufferPointer(), indices.data(), ibByteSize);

geo->VertexBufferGPU = d3dUtil::CreateDefaultBuffer(md3dDevice.Get(),
                                                    mCommandList.Get(), vertices.data(), vbByteSize, geo->VertexBufferUploader);

geo->IndexBufferGPU = d3dUtil::CreateDefaultBuffer(md3dDevice.Get(),
                                                   mCommandList.Get(), indices.data(), ibByteSize, geo->IndexBufferUploader);

geo->VertexByteStride = sizeof(Vertex);
geo->VertexBufferByteSize = vbByteSize;
geo->IndexFormat = DXGI_FORMAT_R16_UINT;
geo->IndexBufferByteSize = ibByteSize;

SubmeshGeometry submesh;
submesh.IndexCount = (UINT)indices.size();
submesh.StartIndexLocation = 0;
submesh.BaseVertexLocation = 0;

geo->DrawArgs["box"] = submesh;

mGeometries["boxGeo"] = std::move(geo);

  6. 生成公告板

    //公告板的中心位置、宽高
struct TreeSpriteVertex
{
    XMFLOAT3 Pos;
    XMFLOAT2 Size;
};

static const int treeCount = 16;	//树的个数
std::array<TreeSpriteVertex, 16> vertices;
for(UINT i = 0; i < treeCount; ++i)
{
    //随机生成公告板的位置
    float x = MathHelper::RandF(-45.0f, 45.0f);
    float z = MathHelper::RandF(-45.0f, 45.0f);
    float y = GetHillsHeight(x, z);

    // 绘制的树要比陆地高
    y += 8.0f;

    vertices[i].Pos = XMFLOAT3(x, y, z);
    vertices[i].Size = XMFLOAT2(20.0f, 20.0f);
}

std::array<std::uint16_t, 16> indices =
{
    0, 1, 2, 3, 4, 5, 6, 7,
    8, 9, 10, 11, 12, 13, 14, 15
};

const UINT vbByteSize = (UINT)vertices.size() * sizeof(TreeSpriteVertex);
const UINT ibByteSize = (UINT)indices.size() * sizeof(std::uint16_t);

auto geo = std::make_unique<MeshGeometry>();
geo->Name = "treeSpritesGeo";

ThrowIfFailed(D3DCreateBlob(vbByteSize, &geo->VertexBufferCPU));
CopyMemory(geo->VertexBufferCPU->GetBufferPointer(), vertices.data(), vbByteSize);

ThrowIfFailed(D3DCreateBlob(ibByteSize, &geo->IndexBufferCPU));
CopyMemory(geo->IndexBufferCPU->GetBufferPointer(), indices.data(), ibByteSize);

geo->VertexBufferGPU = d3dUtil::CreateDefaultBuffer(md3dDevice.Get(),
                                                    mCommandList.Get(), vertices.data(), vbByteSize, geo->VertexBufferUploader);

geo->IndexBufferGPU = d3dUtil::CreateDefaultBuffer(md3dDevice.Get(),
                                                   mCommandList.Get(), indices.data(), ibByteSize, geo->IndexBufferUploader);

geo->VertexByteStride = sizeof(TreeSpriteVertex);
geo->VertexBufferByteSize = vbByteSize;
geo->IndexFormat = DXGI_FORMAT_R16_UINT;
geo->IndexBufferByteSize = ibByteSize;

SubmeshGeometry submesh;
submesh.IndexCount = (UINT)indices.size();
submesh.StartIndexLocation = 0;
submesh.BaseVertexLocation = 0;

geo->DrawArgs["points"] = submesh;

mGeometries["treeSpritesGeo"] = std::move(geo);

  7. 定义材质

    auto grass = std::make_unique<Material>();
grass->Name = "grass";
grass->MatCBIndex = 0;
grass->DiffuseSrvHeapIndex = 0;
grass->DiffuseAlbedo = XMFLOAT4(1.0f, 1.0f, 1.0f, 1.0f);
grass->FresnelR0 = XMFLOAT3(0.01f, 0.01f, 0.01f);
grass->Roughness = 0.125f;

// This is not a good water material definition, but we do not have all the rendering
// tools we need (transparency, environment reflection), so we fake it for now.
auto water = std::make_unique<Material>();
water->Name = "water";
water->MatCBIndex = 1;
water->DiffuseSrvHeapIndex = 1;
water->DiffuseAlbedo = XMFLOAT4(1.0f, 1.0f, 1.0f, 0.5f);
water->FresnelR0 = XMFLOAT3(0.1f, 0.1f, 0.1f);
water->Roughness = 0.0f;

auto wirefence = std::make_unique<Material>();
wirefence->Name = "wirefence";
wirefence->MatCBIndex = 2;
wirefence->DiffuseSrvHeapIndex = 2;
wirefence->DiffuseAlbedo = XMFLOAT4(1.0f, 1.0f, 1.0f, 1.0f);
wirefence->FresnelR0 = XMFLOAT3(0.02f, 0.02f, 0.02f);
wirefence->Roughness = 0.25f;

auto treeSprites = std::make_unique<Material>();
treeSprites->Name = "treeSprites";
treeSprites->MatCBIndex = 3;
treeSprites->DiffuseSrvHeapIndex = 3;
treeSprites->DiffuseAlbedo = XMFLOAT4(1.0f, 1.0f, 1.0f, 1.0f);
treeSprites->FresnelR0 = XMFLOAT3(0.01f, 0.01f, 0.01f);
treeSprites->Roughness = 0.125f;

mMaterials["grass"] = std::move(grass);
mMaterials["water"] = std::move(water);
mMaterials["wirefence"] = std::move(wirefence);
mMaterials["treeSprites"] = std::move(treeSprites);

  8. 生成渲染项

    //每帧渲染需要的数据
auto wavesRitem = std::make_unique<RenderItem>();
wavesRitem->World = MathHelper::Identity4x4();
XMStoreFloat4x4(&wavesRitem->TexTransform, XMMatrixScaling(5.0f, 5.0f, 1.0f));
wavesRitem->ObjCBIndex = 0;
wavesRitem->Mat = mMaterials["water"].get();
wavesRitem->Geo = mGeometries["waterGeo"].get();
wavesRitem->PrimitiveType = D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST;
wavesRitem->IndexCount = wavesRitem->Geo->DrawArgs["grid"].IndexCount;
wavesRitem->StartIndexLocation = wavesRitem->Geo->DrawArgs["grid"].StartIndexLocation;
wavesRitem->BaseVertexLocation = wavesRitem->Geo->DrawArgs["grid"].BaseVertexLocation;

mWavesRitem = wavesRitem.get();

mRitemLayer[(int)RenderLayer::Transparent].push_back(wavesRitem.get());

auto gridRitem = std::make_unique<RenderItem>();
gridRitem->World = MathHelper::Identity4x4();
XMStoreFloat4x4(&gridRitem->TexTransform, XMMatrixScaling(5.0f, 5.0f, 1.0f));
gridRitem->ObjCBIndex = 1;
gridRitem->Mat = mMaterials["grass"].get();
gridRitem->Geo = mGeometries["landGeo"].get();
gridRitem->PrimitiveType = D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST;
gridRitem->IndexCount = gridRitem->Geo->DrawArgs["grid"].IndexCount;
gridRitem->StartIndexLocation = gridRitem->Geo->DrawArgs["grid"].StartIndexLocation;
gridRitem->BaseVertexLocation = gridRitem->Geo->DrawArgs["grid"].BaseVertexLocation;

mRitemLayer[(int)RenderLayer::Opaque].push_back(gridRitem.get());

auto boxRitem = std::make_unique<RenderItem>();
XMStoreFloat4x4(&boxRitem->World, XMMatrixTranslation(3.0f, 2.0f, -9.0f));
boxRitem->ObjCBIndex = 2;
boxRitem->Mat = mMaterials["wirefence"].get();
boxRitem->Geo = mGeometries["boxGeo"].get();
boxRitem->PrimitiveType = D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST;
boxRitem->IndexCount = boxRitem->Geo->DrawArgs["box"].IndexCount;
boxRitem->StartIndexLocation = boxRitem->Geo->DrawArgs["box"].StartIndexLocation;
boxRitem->BaseVertexLocation = boxRitem->Geo->DrawArgs["box"].BaseVertexLocation;

mRitemLayer[(int)RenderLayer::AlphaTested].push_back(boxRitem.get());

auto treeSpritesRitem = std::make_unique<RenderItem>();
treeSpritesRitem->World = MathHelper::Identity4x4();
treeSpritesRitem->ObjCBIndex = 3;
treeSpritesRitem->Mat = mMaterials["treeSprites"].get();
treeSpritesRitem->Geo = mGeometries["treeSpritesGeo"].get();
treeSpritesRitem->PrimitiveType = D3D11_PRIMITIVE_TOPOLOGY_POINTLIST;
treeSpritesRitem->IndexCount = treeSpritesRitem->Geo->DrawArgs["points"].IndexCount;
treeSpritesRitem->StartIndexLocation = treeSpritesRitem->Geo->DrawArgs["points"].StartIndexLocation;
treeSpritesRitem->BaseVertexLocation = treeSpritesRitem->Geo->DrawArgs["points"].BaseVertexLocation;

mRitemLayer[(int)RenderLayer::AlphaTestedTreeSprites].push_back(treeSpritesRitem.get());

mAllRitems.push_back(std::move(wavesRitem));
mAllRitems.push_back(std::move(gridRitem));
mAllRitems.push_back(std::move(boxRitem));
mAllRitems.push_back(std::move(treeSpritesRitem));

  9. 生成帧资源

    void TreeBillboardsApp::BuildFrameResources()
{
    for(int i = 0; i < gNumFrameResources; ++i)
    {
        mFrameResources.push_back(std::make_unique<FrameResource>(md3dDevice.Get(),
            1, (UINT)mAllRitems.size(), (UINT)mMaterials.size(), mWaves->VertexCount()));
    }
}

reference

Directx12 3D 游戏开发实战

标签：std,1.0,DX,几何,indices,顶点,geo,着色器
From： https://www.cnblogs.com/chenglixue/p/17166168.html

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