DirectX/10.0/Direct3D/漫反射光照

在本教程中，我將介紹如何使用漫反射光照和 DirectX 11 來照亮 3D 物件。我們將從上一個教程的程式碼開始，並對其進行修改。

我們將要實現的漫反射光照型別稱為方向光照。方向光照類似於太陽照亮地球的方式。它是一個距離很遠的燈光源，根據它發出光的方向，可以確定任何物體上的光照量。但是，與環境光照（我們很快將介紹的另一種光照模型）不同，它不會照亮它沒有直接接觸到的表面。

我選擇方向光照作為起點，因為它非常容易在視覺上進行除錯。此外，由於它只需要一個方向，因此公式比其他型別的漫反射光照（如聚光燈和點光源）更簡單。

在 DirectX 11 中，漫反射光照的實現是透過頂點著色器和畫素著色器完成的。漫反射光照只需要任何我們要照亮的多邊形的朝向和法線向量。朝向是一個您定義的單個向量，您可以使用構成多邊形的三個頂點來計算任何多邊形的法線。在本教程中，我們還將在光照方程中實現漫反射光的顏色。

框架

在本教程中，我們將建立一個名為 LightClass 的新類，它將代表場景中的光源。LightClass 除了儲存光的朝向和顏色之外，實際上不會做任何其他事情。我們還將刪除 TextureShaderClass，並將其替換為 LightshaderClass，它處理模型上的光照著色。隨著新類的新增，框架現在看起來如下所示

我們將從程式碼部分開始，看看 HLSL 光照著色器。你會注意到，光照著色器只是上一個教程中紋理著色器的更新版本。

Light.vs

////////////////////////////////////////////////////////////////////////////////
// Filename: light.vs
////////////////////////////////////////////////////////////////////////////////


/////////////
// GLOBALS //
/////////////
cbuffer MatrixBuffer
{
    matrix worldMatrix;
    matrix viewMatrix;
    matrix projectionMatrix;
};

這兩個結構現在都有一個 3 個浮點數的法線向量。法線向量用於透過使用法線方向和光照方向之間的角度來計算光照量。

//////////////
// TYPEDEFS //
//////////////
struct VertexInputType
{
    float4 position : POSITION;
    float2 tex : TEXCOORD0;
    float3 normal : NORMAL;
};

struct PixelInputType
{
    float4 position : SV_POSITION;
    float2 tex : TEXCOORD0;
    float3 normal : NORMAL;
};


////////////////////////////////////////////////////////////////////////////////
// Vertex Shader
////////////////////////////////////////////////////////////////////////////////
PixelInputType LightVertexShader(VertexInputType input)
{
    PixelInputType output;
    

    // Change the position vector to be 4 units for proper matrix calculations.
    input.position.w = 1.0f;

    // Calculate the position of the vertex against the world, view, and projection matrices.
    output.position = mul(input.position, worldMatrix);
    output.position = mul(output.position, viewMatrix);
    output.position = mul(output.position, projectionMatrix);
    
    // Store the texture coordinates for the pixel shader.
    output.tex = input.tex;

此頂點的法線向量是在世界空間中計算的，然後在被髮送到畫素著色器作為輸入之前被標準化。

    // Calculate the normal vector against the world matrix only.
    output.normal = mul(input.normal, (float3x3)worldMatrix);
	
    // Normalize the normal vector.
    output.normal = normalize(output.normal);

    return output;
}

Light.ps

////////////////////////////////////////////////////////////////////////////////
// Filename: light.ps
////////////////////////////////////////////////////////////////////////////////


/////////////
// GLOBALS //
/////////////
Texture2D shaderTexture;
SamplerState SampleType;

我們在 LightBuffer 中有兩個新的全域性變數，它們儲存著漫反射光照的顏色和光的朝向。這兩個變數將從新的 LightClass 物件中的值設定。

cbuffer LightBuffer
{
    float4 diffuseColor;
    float3 lightDirection;
    float padding;
};


//////////////
// TYPEDEFS //
//////////////
struct PixelInputType
{
    float4 position : SV_POSITION;
    float2 tex : TEXCOORD0;
    float3 normal : NORMAL;
};


////////////////////////////////////////////////////////////////////////////////
// Pixel Shader
////////////////////////////////////////////////////////////////////////////////
float4 LightPixelShader(PixelInputType input) : SV_TARGET
{
    float4 textureColor;
    float3 lightDir;
    float lightIntensity;
    float4 color;


    // Sample the pixel color from the texture using the sampler at this texture coordinate location.
    textureColor = shaderTexture.Sample(SampleType, input.tex);

這是前面討論的光照方程現在被實現的地方。光照強度值被計算為三角形法線向量和光照方向向量之間的點積。

    // Invert the light direction for calculations.
    lightDir = -lightDirection;

    // Calculate the amount of light on this pixel.
    lightIntensity = saturate(dot(input.normal, lightDir));

最後，光的漫反射值與紋理畫素值結合起來，產生顏色結果。

    // Determine the final amount of diffuse color based on the diffuse color combined with the light intensity.
    color = saturate(diffuseColor * lightIntensity);

    // Multiply the texture pixel and the final diffuse color to get the final pixel color result.
    color = color * textureColor;

    return color;
}

Lightshaderclass.h

新的 LightShaderClass 只是上一個教程中 TextureShaderClass 的略微重寫版本，以合併光照。

////////////////////////////////////////////////////////////////////////////////
// Filename: lightshaderclass.h
////////////////////////////////////////////////////////////////////////////////
#ifndef _LIGHTSHADERCLASS_H_
#define _LIGHTSHADERCLASS_H_


//////////////
// INCLUDES //
//////////////
#include <d3d11.h>
#include <d3dx10math.h>
#include <d3dx11async.h>
#include <fstream>
using namespace std;


////////////////////////////////////////////////////////////////////////////////
// Class name: LightShaderClass
////////////////////////////////////////////////////////////////////////////////
class LightShaderClass
{
private:
	struct MatrixBufferType
	{
		D3DXMATRIX world;
		D3DXMATRIX view;
		D3DXMATRIX projection;
	};

新的 LightBufferType 結構將用於儲存光照資訊。此 typedef 與畫素著色器中的新 typedef 相同。請注意，我添加了一個額外的浮點數進行大小填充，以確保結構是 16 的倍數。由於沒有額外浮點數的結構只有 28 個位元組，如果我們使用 sizeof(LightBufferType)，CreateBuffer 會失敗，因為它需要大小是 16 的倍數才能成功。

	struct LightBufferType
	{
		D3DXVECTOR4 diffuseColor;
		D3DXVECTOR3 lightDirection;
		float padding;  // Added extra padding so structure is a multiple of 16 for CreateBuffer function requirements.
	};

public:
	LightShaderClass();
	LightShaderClass(const LightShaderClass&);
	~LightShaderClass();

	bool Initialize(ID3D11Device*, HWND);
	void Shutdown();
	bool Render(ID3D11DeviceContext*, int, D3DXMATRIX, D3DXMATRIX, D3DXMATRIX, ID3D11ShaderResourceView*, D3DXVECTOR3, D3DXVECTOR4);

private:
	bool InitializeShader(ID3D11Device*, HWND, WCHAR*, WCHAR*);
	void ShutdownShader();
	void OutputShaderErrorMessage(ID3D10Blob*, HWND, WCHAR*);

	bool SetShaderParameters(ID3D11DeviceContext*, D3DXMATRIX, D3DXMATRIX, D3DXMATRIX, ID3D11ShaderResourceView*, D3DXVECTOR3, D3DXVECTOR4);
	void RenderShader(ID3D11DeviceContext*, int);

private:
	ID3D11VertexShader* m_vertexShader;
	ID3D11PixelShader* m_pixelShader;
	ID3D11InputLayout* m_layout;
	ID3D11SamplerState* m_sampleState;
	ID3D11Buffer* m_matrixBuffer;

有一個用於光照資訊（顏色和朝向）的新私有常量緩衝區。光照緩衝區將被此類用於設定 HLSL 畫素著色器內部的全域性光照變數。

	ID3D11Buffer* m_lightBuffer;
};

#endif

Lightshaderclass.cpp

////////////////////////////////////////////////////////////////////////////////
// Filename: lightshaderclass.cpp
////////////////////////////////////////////////////////////////////////////////
#include "lightshaderclass.h"


LightShaderClass::LightShaderClass()
{
	m_vertexShader = 0;
	m_pixelShader = 0;
	m_layout = 0;
	m_sampleState = 0;
	m_matrixBuffer = 0;

在類建構函式中將新的光照常量緩衝區設定為 null。

	m_lightBuffer = 0;
}


LightShaderClass::LightShaderClass(const LightShaderClass& other)
{
}


LightShaderClass::~LightShaderClass()
{
}


bool LightShaderClass::Initialize(ID3D11Device* device, HWND hwnd)
{
	bool result;

新的 light.vs 和 light.ps HLSL 著色器檔案被用作初始化光照著色器的輸入。

	// Initialize the vertex and pixel shaders.
	result = InitializeShader(device, hwnd, L"../Engine/light.vs", L"../Engine/light.ps");
	if(!result)
	{
		return false;
	}

	return true;
}


void LightShaderClass::Shutdown()
{
	// Shutdown the vertex and pixel shaders as well as the related objects.
	ShutdownShader();

	return;
}

Render 函式現在將光照方向和漫反射光照顏色作為輸入。然後，這些變數被髮送到 SetShaderParameters 函式，最後在著色器本身內部設定。

bool LightShaderClass::Render(ID3D11DeviceContext* deviceContext, int indexCount, D3DXMATRIX worldMatrix, D3DXMATRIX viewMatrix, 
			      D3DXMATRIX projectionMatrix, ID3D11ShaderResourceView* texture, D3DXVECTOR3 lightDirection, D3DXVECTOR4 diffuseColor)
{
	bool result;


	// Set the shader parameters that it will use for rendering.
	result = SetShaderParameters(deviceContext, worldMatrix, viewMatrix, projectionMatrix, texture, lightDirection, diffuseColor);
	if(!result)
	{
		return false;
	}

	// Now render the prepared buffers with the shader.
	RenderShader(deviceContext, indexCount);

	return true;
}


bool LightShaderClass::InitializeShader(ID3D11Device* device, HWND hwnd, WCHAR* vsFilename, WCHAR* psFilename)
{
	HRESULT result;
	ID3D10Blob* errorMessage;
	ID3D10Blob* vertexShaderBuffer;
	ID3D10Blob* pixelShaderBuffer;

polygonLayout 變數已被更改為具有三個元素，而不是兩個。這是為了它可以容納佈局中的法線向量。

	D3D11_INPUT_ELEMENT_DESC polygonLayout[3];
	unsigned int numElements;
	D3D11_SAMPLER_DESC samplerDesc;
	D3D11_BUFFER_DESC matrixBufferDesc;

我們還添加了一個新的描述變數，用於光照常量緩衝區。

	D3D11_BUFFER_DESC lightBufferDesc;


	// Initialize the pointers this function will use to null.
	errorMessage = 0;
	vertexShaderBuffer = 0;
	pixelShaderBuffer = 0;

載入新的 light 頂點著色器。

	// Compile the vertex shader code.
	result = D3DX11CompileFromFile(vsFilename, NULL, NULL, "LightVertexShader", "vs_5_0", D3D10_SHADER_ENABLE_STRICTNESS, 0, NULL, 
				       &vertexShaderBuffer, &errorMessage, NULL);
	if(FAILED(result))
	{
		// If the shader failed to compile it should have writen something to the error message.
		if(errorMessage)
		{
			OutputShaderErrorMessage(errorMessage, hwnd, vsFilename);
		}
		// If there was nothing in the error message then it simply could not find the shader file itself.
		else
		{
			MessageBox(hwnd, vsFilename, L"Missing Shader File", MB_OK);
		}

		return false;
	}

載入新的 light 畫素著色器。

	// Compile the pixel shader code.
	result = D3DX11CompileFromFile(psFilename, NULL, NULL, "LightPixelShader", "ps_5_0", D3D10_SHADER_ENABLE_STRICTNESS, 0, NULL, 
				       &pixelShaderBuffer, &errorMessage, NULL);
	if(FAILED(result))
	{
		// If the shader failed to compile it should have writen something to the error message.
		if(errorMessage)
		{
			OutputShaderErrorMessage(errorMessage, hwnd, psFilename);
		}
		// If there was nothing in the error message then it simply could not find the file itself.
		else
		{
			MessageBox(hwnd, psFilename, L"Missing Shader File", MB_OK);
		}

		return false;
	}

	// Create the vertex shader from the buffer.
	result = device->CreateVertexShader(vertexShaderBuffer->GetBufferPointer(), vertexShaderBuffer->GetBufferSize(), NULL, &m_vertexShader);
	if(FAILED(result))
	{
		return false;
	}

	// Create the pixel shader from the buffer.
	result = device->CreatePixelShader(pixelShaderBuffer->GetBufferPointer(), pixelShaderBuffer->GetBufferSize(), NULL, &m_pixelShader);
	if(FAILED(result))
	{
		return false;
	}

	// Create the vertex input layout description.
	// This setup needs to match the VertexType structure in the ModelClass and in the shader.
	polygonLayout[0].SemanticName = "POSITION";
	polygonLayout[0].SemanticIndex = 0;
	polygonLayout[0].Format = DXGI_FORMAT_R32G32B32_FLOAT;
	polygonLayout[0].InputSlot = 0;
	polygonLayout[0].AlignedByteOffset = 0;
	polygonLayout[0].InputSlotClass = D3D11_INPUT_PER_VERTEX_DATA;
	polygonLayout[0].InstanceDataStepRate = 0;

	polygonLayout[1].SemanticName = "TEXCOORD";
	polygonLayout[1].SemanticIndex = 0;
	polygonLayout[1].Format = DXGI_FORMAT_R32G32_FLOAT;
	polygonLayout[1].InputSlot = 0;
	polygonLayout[1].AlignedByteOffset = D3D11_APPEND_ALIGNED_ELEMENT;
	polygonLayout[1].InputSlotClass = D3D11_INPUT_PER_VERTEX_DATA;
	polygonLayout[1].InstanceDataStepRate = 0;

著色器初始化的一個主要變化是這裡在 polygonLayout 中。我們添加了用於光照計算的第三個元素，用於法線向量。語義名稱是 NORMAL，格式是常規的 DXGI_FORMAT_R32G32B32_FLOAT，它處理法線向量的 x、y 和 z 的 3 個浮點數。該佈局現在將與 HLSL 頂點著色器的預期輸入匹配。

	polygonLayout[2].SemanticName = "NORMAL";
	polygonLayout[2].SemanticIndex = 0;
	polygonLayout[2].Format = DXGI_FORMAT_R32G32B32_FLOAT;
	polygonLayout[2].InputSlot = 0;
	polygonLayout[2].AlignedByteOffset = D3D11_APPEND_ALIGNED_ELEMENT;
	polygonLayout[2].InputSlotClass = D3D11_INPUT_PER_VERTEX_DATA;
	polygonLayout[2].InstanceDataStepRate = 0;

	// Get a count of the elements in the layout.
	numElements = sizeof(polygonLayout) / sizeof(polygonLayout[0]);

	// Create the vertex input layout.
	result = device->CreateInputLayout(polygonLayout, numElements, vertexShaderBuffer->GetBufferPointer(), vertexShaderBuffer->GetBufferSize(), 
					   &m_layout);
	if(FAILED(result))
	{
		return false;
	}

	// Release the vertex shader buffer and pixel shader buffer since they are no longer needed.
	vertexShaderBuffer->Release();
	vertexShaderBuffer = 0;

	pixelShaderBuffer->Release();
	pixelShaderBuffer = 0;

	// Create a texture sampler state description.
	samplerDesc.Filter = D3D11_FILTER_MIN_MAG_MIP_LINEAR;
	samplerDesc.AddressU = D3D11_TEXTURE_ADDRESS_WRAP;
	samplerDesc.AddressV = D3D11_TEXTURE_ADDRESS_WRAP;
	samplerDesc.AddressW = D3D11_TEXTURE_ADDRESS_WRAP;
	samplerDesc.MipLODBias = 0.0f;
	samplerDesc.MaxAnisotropy = 1;
	samplerDesc.ComparisonFunc = D3D11_COMPARISON_ALWAYS;
	samplerDesc.BorderColor[0] = 0;
	samplerDesc.BorderColor[1] = 0;
	samplerDesc.BorderColor[2] = 0;
	samplerDesc.BorderColor[3] = 0;
	samplerDesc.MinLOD = 0;
	samplerDesc.MaxLOD = D3D11_FLOAT32_MAX;

	// Create the texture sampler state.
	result = device->CreateSamplerState(&samplerDesc, &m_sampleState);
	if(FAILED(result))
	{
		return false;
	}

	// Setup the description of the dynamic matrix constant buffer that is in the vertex shader.
	matrixBufferDesc.Usage = D3D11_USAGE_DYNAMIC;
	matrixBufferDesc.ByteWidth = sizeof(MatrixBufferType);
	matrixBufferDesc.BindFlags = D3D11_BIND_CONSTANT_BUFFER;
	matrixBufferDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
	matrixBufferDesc.MiscFlags = 0;
	matrixBufferDesc.StructureByteStride = 0;

	// Create the constant buffer pointer so we can access the vertex shader constant buffer from within this class.
	result = device->CreateBuffer(&matrixBufferDesc, NULL, &m_matrixBuffer);
	if(FAILED(result))
	{
		return false;
	}

在這裡，我們設定光照常量緩衝區描述，它將處理漫反射光照顏色和光照方向。注意常量緩衝區的大小，如果它們不是 16 的倍數，則需要在它們末尾新增額外的空間，否則 CreateBuffer 函式將失敗。在本例中，常量緩衝區為 28 位元組，填充 4 位元組，使其變為 32 位元組。

	// Setup the description of the light dynamic constant buffer that is in the pixel shader.
	// Note that ByteWidth always needs to be a multiple of 16 if using D3D11_BIND_CONSTANT_BUFFER or CreateBuffer will fail.
	lightBufferDesc.Usage = D3D11_USAGE_DYNAMIC;
	lightBufferDesc.ByteWidth = sizeof(LightBufferType);
	lightBufferDesc.BindFlags = D3D11_BIND_CONSTANT_BUFFER;
	lightBufferDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
	lightBufferDesc.MiscFlags = 0;
	lightBufferDesc.StructureByteStride = 0;

	// Create the constant buffer pointer so we can access the vertex shader constant buffer from within this class.
	result = device->CreateBuffer(&lightBufferDesc, NULL, &m_lightBuffer);
	if(FAILED(result))
	{
		return false;
	}

	return true;
}


void LightShaderClass::ShutdownShader()
{

新的光照常量緩衝區在 ShutdownShader 函式中被釋放。

	// Release the light constant buffer.
	if(m_lightBuffer)
	{
		m_lightBuffer->Release();
		m_lightBuffer = 0;
	}

	// Release the matrix constant buffer.
	if(m_matrixBuffer)
	{
		m_matrixBuffer->Release();
		m_matrixBuffer = 0;
	}

	// Release the sampler state.
	if(m_sampleState)
	{
		m_sampleState->Release();
		m_sampleState = 0;
	}

	// Release the layout.
	if(m_layout)
	{
		m_layout->Release();
		m_layout = 0;
	}

	// Release the pixel shader.
	if(m_pixelShader)
	{
		m_pixelShader->Release();
		m_pixelShader = 0;
	}

	// Release the vertex shader.
	if(m_vertexShader)
	{
		m_vertexShader->Release();
		m_vertexShader = 0;
	}

	return;
}


void LightShaderClass::OutputShaderErrorMessage(ID3D10Blob* errorMessage, HWND hwnd, WCHAR* shaderFilename)
{
	char* compileErrors;
	unsigned long bufferSize, i;
	ofstream fout;


	// Get a pointer to the error message text buffer.
	compileErrors = (char*)(errorMessage->GetBufferPointer());

	// Get the length of the message.
	bufferSize = errorMessage->GetBufferSize();

	// Open a file to write the error message to.
	fout.open("shader-error.txt");

	// Write out the error message.
	for(i=0; i<bufferSize; i++)
	{
		fout Release();
	errorMessage = 0;

	// Pop a message up on the screen to notify the user to check the text file for compile errors.
	MessageBox(hwnd, L"Error compiling shader.  Check shader-error.txt for message.", shaderFilename, MB_OK);

	return;
}

SetShaderParameters 函式現在將 lightDirection 和 diffuseColor 作為輸入。

bool LightShaderClass::SetShaderParameters(ID3D11DeviceContext* deviceContext, D3DXMATRIX worldMatrix, D3DXMATRIX viewMatrix, 
					   D3DXMATRIX projectionMatrix, ID3D11ShaderResourceView* texture, D3DXVECTOR3 lightDirection, 
					   D3DXVECTOR4 diffuseColor)
{
	HRESULT result;
	D3D11_MAPPED_SUBRESOURCE mappedResource;
	unsigned int bufferNumber;
	MatrixBufferType* dataPtr;
	LightBufferType* dataPtr2;


	// Transpose the matrices to prepare them for the shader.
	D3DXMatrixTranspose(&worldMatrix, &worldMatrix);
	D3DXMatrixTranspose(&viewMatrix, &viewMatrix);
	D3DXMatrixTranspose(&projectionMatrix, &projectionMatrix);

	// Lock the constant buffer so it can be written to.
	result = deviceContext->Map(m_matrixBuffer, 0, D3D11_MAP_WRITE_DISCARD, 0, &mappedResource);
	if(FAILED(result))
	{
		return false;
	}

	// Get a pointer to the data in the constant buffer.
	dataPtr = (MatrixBufferType*)mappedResource.pData;

	// Copy the matrices into the constant buffer.
	dataPtr->world = worldMatrix;
	dataPtr->view = viewMatrix;
	dataPtr->projection = projectionMatrix;

	// Unlock the constant buffer.
	deviceContext->Unmap(m_matrixBuffer, 0);

	// Set the position of the constant buffer in the vertex shader.
	bufferNumber = 0;

	// Now set the constant buffer in the vertex shader with the updated values.
	deviceContext->VSSetConstantBuffers(bufferNumber, 1, &m_matrixBuffer);

	// Set shader texture resource in the pixel shader.
	deviceContext->PSSetShaderResources(0, 1, &texture);

光照常量緩衝區的設定方式與矩陣常量緩衝區相同。我們首先鎖定緩衝區並獲取指向它的指標。之後，我們使用該指標設定漫反射光照顏色和光照方向。資料設定完成後，我們解鎖緩衝區，然後將其設定在畫素著色器中。注意，我們使用 PSSetConstantBuffers 函式而不是 VSSetConstantBuffers，因為這是我們要設定的畫素著色器緩衝區。

	// Lock the light constant buffer so it can be written to.
	result = deviceContext->Map(m_lightBuffer, 0, D3D11_MAP_WRITE_DISCARD, 0, &mappedResource);
	if(FAILED(result))
	{
		return false;
	}

	// Get a pointer to the data in the constant buffer.
	dataPtr2 = (LightBufferType*)mappedResource.pData;

	// Copy the lighting variables into the constant buffer.
	dataPtr2->diffuseColor = diffuseColor;
	dataPtr2->lightDirection = lightDirection;
	dataPtr2->padding = 0.0f;

	// Unlock the constant buffer.
	deviceContext->Unmap(m_lightBuffer, 0);

	// Set the position of the light constant buffer in the pixel shader.
	bufferNumber = 0;

	// Finally set the light constant buffer in the pixel shader with the updated values.
	deviceContext->PSSetConstantBuffers(bufferNumber, 1, &m_lightBuffer);

	return true;
}


void LightShaderClass::RenderShader(ID3D11DeviceContext* deviceContext, int indexCount)
{
	// Set the vertex input layout.
	deviceContext->IASetInputLayout(m_layout);

	// Set the vertex and pixel shaders that will be used to render this triangle.
	deviceContext->VSSetShader(m_vertexShader, NULL, 0);
	deviceContext->PSSetShader(m_pixelShader, NULL, 0);

	// Set the sampler state in the pixel shader.
	deviceContext->PSSetSamplers(0, 1, &m_sampleState);

	// Render the triangle.
	deviceContext->DrawIndexed(indexCount, 0, 0);

	return;
}

Modelclass.h

ModelClass 已被稍微修改以處理光照元件。

////////////////////////////////////////////////////////////////////////////////
// Filename: modelclass.h
////////////////////////////////////////////////////////////////////////////////
#ifndef _MODELCLASS_H_
#define _MODELCLASS_H_


//////////////
// INCLUDES //
//////////////
#include <d3d11.h>
#include <d3dx10math.h>


///////////////////////
// MY CLASS INCLUDES //
///////////////////////
#include "textureclass.h"


////////////////////////////////////////////////////////////////////////////////
// Class name: ModelClass
////////////////////////////////////////////////////////////////////////////////
class ModelClass
{
private:

VertexType 結構現在有一個法線向量，以適應光照。

	struct VertexType
	{
		D3DXVECTOR3 position;
		D3DXVECTOR2 texture;

		D3DXVECTOR3 normal;

	};

public:
	ModelClass();
	ModelClass(const ModelClass&);
	~ModelClass();

	bool Initialize(ID3D11Device*, WCHAR*);
	void Shutdown();
	void Render(ID3D11DeviceContext*);

	int GetIndexCount();
	ID3D11ShaderResourceView* GetTexture();


private:
	bool InitializeBuffers(ID3D11Device*);
	void ShutdownBuffers();
	void RenderBuffers(ID3D11DeviceContext*);

	bool LoadTexture(ID3D11Device*, WCHAR*);
	void ReleaseTexture();

private:
	ID3D11Buffer *m_vertexBuffer, *m_indexBuffer;
	int m_vertexCount, m_indexCount;
	TextureClass* m_Texture;
};

#endif

Modelclass.cpp

////////////////////////////////////////////////////////////////////////////////
// Filename: modelclass.cpp
////////////////////////////////////////////////////////////////////////////////
#include "modelclass.h"


ModelClass::ModelClass()
{
	m_vertexBuffer = 0;
	m_indexBuffer = 0;
	m_Texture = 0;
}


ModelClass::ModelClass(const ModelClass& other)
{
}


ModelClass::~ModelClass()
{
}


bool ModelClass::Initialize(ID3D11Device* device, WCHAR* textureFilename)
{
	bool result;


	// Initialize the vertex and index buffers.
	result = InitializeBuffers(device);
	if(!result)
	{
		return false;
	}

	// Load the texture for this model.
	result = LoadTexture(device, textureFilename);
	if(!result)
	{
		return false;
	}

	return true;
}


void ModelClass::Shutdown()
{
	// Release the model texture.
	ReleaseTexture();

	// Shutdown the vertex and index buffers.
	ShutdownBuffers();

	return;
}


void ModelClass::Render(ID3D11DeviceContext* deviceContext)
{
	// Put the vertex and index buffers on the graphics pipeline to prepare them for drawing.
	RenderBuffers(deviceContext);

	return;
}


int ModelClass::GetIndexCount()
{
	return m_indexCount;
}


ID3D11ShaderResourceView* ModelClass::GetTexture()
{
	return m_Texture->GetTexture();
}


bool ModelClass::InitializeBuffers(ID3D11Device* device)
{
	VertexType* vertices;
	unsigned long* indices;
	D3D11_BUFFER_DESC vertexBufferDesc, indexBufferDesc;
	D3D11_SUBRESOURCE_DATA vertexData, indexData;
	HRESULT result;


	// Set the number of vertices in the vertex array.
	m_vertexCount = 3;

	// Set the number of indices in the index array.
	m_indexCount = 3;

	// Create the vertex array.
	vertices = new VertexType[m_vertexCount];
	if(!vertices)
	{
		return false;
	}

	// Create the index array.
	indices = new unsigned long[m_indexCount];
	if(!indices)
	{
		return false;
	}

InitializeBuffers 函式的唯一變化是這裡在頂點設定中。每個頂點現在都有與之相關的法線，用於光照計算。法線是一條垂直於多邊形面的線，以便可以計算出該面指向的確切方向。為了簡單起見，我透過將每個 Z 元件設定為 -1.0f 來沿著 Z 軸設定每個頂點的法線，這使得法線指向觀察者。

	// Load the vertex array with data.
	vertices[0].position = D3DXVECTOR3(-1.0f, -1.0f, 0.0f);  // Bottom left.
	vertices[0].texture = D3DXVECTOR2(0.0f, 1.0f);

	vertices[0].normal = D3DXVECTOR3(0.0f, 0.0f, -1.0f);

	vertices[1].position = D3DXVECTOR3(0.0f, 1.0f, 0.0f);  // Top middle.
	vertices[1].texture = D3DXVECTOR2(0.5f, 0.0f);

	vertices[1].normal = D3DXVECTOR3(0.0f, 0.0f, -1.0f);

	vertices[2].position = D3DXVECTOR3(1.0f, -1.0f, 0.0f);  // Bottom right.
	vertices[2].texture = D3DXVECTOR2(1.0f, 1.0f);

	vertices[2].normal = D3DXVECTOR3(0.0f, 0.0f, -1.0f);

	// Load the index array with data.
	indices[0] = 0;  // Bottom left.
	indices[1] = 1;  // Top middle.
	indices[2] = 2;  // Bottom right.

	// Set up the description of the static vertex buffer.
	vertexBufferDesc.Usage = D3D11_USAGE_DEFAULT;
	vertexBufferDesc.ByteWidth = sizeof(VertexType) * m_vertexCount;
	vertexBufferDesc.BindFlags = D3D11_BIND_VERTEX_BUFFER;
	vertexBufferDesc.CPUAccessFlags = 0;
	vertexBufferDesc.MiscFlags = 0;
	vertexBufferDesc.StructureByteStride = 0;

	// Give the subresource structure a pointer to the vertex data.
	vertexData.pSysMem = vertices;
	vertexData.SysMemPitch = 0;
	vertexData.SysMemSlicePitch = 0;

	// Now create the vertex buffer.
	result = device->CreateBuffer(&vertexBufferDesc, &vertexData, &m_vertexBuffer);
	if(FAILED(result))
	{
		return false;
	}

	// Set up the description of the static index buffer.
	indexBufferDesc.Usage = D3D11_USAGE_DEFAULT;
	indexBufferDesc.ByteWidth = sizeof(unsigned long) * m_indexCount;
	indexBufferDesc.BindFlags = D3D11_BIND_INDEX_BUFFER;
	indexBufferDesc.CPUAccessFlags = 0;
	indexBufferDesc.MiscFlags = 0;
	indexBufferDesc.StructureByteStride = 0;

	// Give the subresource structure a pointer to the index data.
	indexData.pSysMem = indices;
	indexData.SysMemPitch = 0;
	indexData.SysMemSlicePitch = 0;

	// Create the index buffer.
	result = device->CreateBuffer(&indexBufferDesc, &indexData, &m_indexBuffer);
	if(FAILED(result))
	{
		return false;
	}

	// Release the arrays now that the vertex and index buffers have been created and loaded.
	delete [] vertices;
	vertices = 0;

	delete [] indices;
	indices = 0;

	return true;
}


void ModelClass::ShutdownBuffers()
{
	// Release the index buffer.
	if(m_indexBuffer)
	{
		m_indexBuffer->Release();
		m_indexBuffer = 0;
	}

	// Release the vertex buffer.
	if(m_vertexBuffer)
	{
		m_vertexBuffer->Release();
		m_vertexBuffer = 0;
	}

	return;
}


void ModelClass::RenderBuffers(ID3D11DeviceContext* deviceContext)
{
	unsigned int stride;
	unsigned int offset;


	// Set vertex buffer stride and offset.
	stride = sizeof(VertexType); 
	offset = 0;
    
	// Set the vertex buffer to active in the input assembler so it can be rendered.
	deviceContext->IASetVertexBuffers(0, 1, &m_vertexBuffer, &stride, &offset);

	// Set the index buffer to active in the input assembler so it can be rendered.
	deviceContext->IASetIndexBuffer(m_indexBuffer, DXGI_FORMAT_R32_UINT, 0);

	// Set the type of primitive that should be rendered from this vertex buffer, in this case triangles.
	deviceContext->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST);

	return;
}


bool ModelClass::LoadTexture(ID3D11Device* device, WCHAR* filename)
{
	bool result;


	// Create the texture object.
	m_Texture = new TextureClass;
	if(!m_Texture)
	{
		return false;
	}

	// Initialize the texture object.
	result = m_Texture->Initialize(device, filename);
	if(!result)
	{
		return false;
	}

	return true;
}


void ModelClass::ReleaseTexture()
{
	// Release the texture object.
	if(m_Texture)
	{
		m_Texture->Shutdown();
		delete m_Texture;
		m_Texture = 0;
	}

	return;
}

Lightclass.h

現在我們將看看新的光照類，它非常簡單。它的目的僅僅是維護光的朝向和顏色。

////////////////////////////////////////////////////////////////////////////////
// Filename: lightclass.h
////////////////////////////////////////////////////////////////////////////////
#ifndef _LIGHTCLASS_H_
#define _LIGHTCLASS_H_


//////////////
// INCLUDES //
//////////////
#include <d3dx10math.h>


////////////////////////////////////////////////////////////////////////////////
// Class name: LightClass
////////////////////////////////////////////////////////////////////////////////
class LightClass
{
public:
	LightClass();
	LightClass(const LightClass&);
	~LightClass();

	void SetDiffuseColor(float, float, float, float);
	void SetDirection(float, float, float);

	D3DXVECTOR4 GetDiffuseColor();
	D3DXVECTOR3 GetDirection();

private:
	D3DXVECTOR4 m_diffuseColor;
	D3DXVECTOR3 m_direction;
};

#endif

Lightclass.cpp

////////////////////////////////////////////////////////////////////////////////
// Filename: lightclass.cpp
////////////////////////////////////////////////////////////////////////////////
#include "lightclass.h"


LightClass::LightClass()
{
}


LightClass::LightClass(const LightClass& other)
{
}


LightClass::~LightClass()
{
}


void LightClass::SetDiffuseColor(float red, float green, float blue, float alpha)
{
	m_diffuseColor = D3DXVECTOR4(red, green, blue, alpha);
	return;
}


void LightClass::SetDirection(float x, float y, float z)
{
	m_direction = D3DXVECTOR3(x, y, z);
	return;
}


D3DXVECTOR4 LightClass::GetDiffuseColor()
{
	return m_diffuseColor;
}


D3DXVECTOR3 LightClass::GetDirection()
{
	return m_direction;
}

Graphicsclass.h

////////////////////////////////////////////////////////////////////////////////
// Filename: graphicsclass.h
////////////////////////////////////////////////////////////////////////////////
#ifndef _GRAPHICSCLASS_H_
#define _GRAPHICSCLASS_H_


///////////////////////
// MY CLASS INCLUDES //
///////////////////////
#include "d3dclass.h"
#include "cameraclass.h"
#include "modelclass.h"

GraphicsClass 現在有兩個新的包含，用於 LightShaderClass 和 LightClass。

#include "lightshaderclass.h"
#include "lightclass.h"

/////////////
// GLOBALS //
/////////////
const bool FULL_SCREEN = true;
const bool VSYNC_ENABLED = true;
const float SCREEN_DEPTH = 1000.0f;
const float SCREEN_NEAR = 0.1f;


////////////////////////////////////////////////////////////////////////////////
// Class name: GraphicsClass
////////////////////////////////////////////////////////////////////////////////
class GraphicsClass
{
public:
	GraphicsClass();
	GraphicsClass(const GraphicsClass&);
	~GraphicsClass();

	bool Initialize(int, int, HWND);
	void Shutdown();
	bool Frame();

private:

現在 Render 函式接受浮點型數值作為輸入。

	bool Render(float);

private:
	D3DClass* m_D3D;
	CameraClass* m_Camera;
	ModelClass* m_Model;

光照著色器和光照物件新增了兩個私有變數。

	LightShaderClass* m_LightShader;
	LightClass* m_Light;

};

#endif

Graphicsclass.cpp

////////////////////////////////////////////////////////////////////////////////
// Filename: graphicsclass.cpp
////////////////////////////////////////////////////////////////////////////////
#include "graphicsclass.h"


GraphicsClass::GraphicsClass()
{
	m_D3D = 0;
	m_Camera = 0;
	m_Model = 0;

光照著色器和光照物件在類建構函式中被設定為 null。

	m_LightShader = 0;
	m_Light = 0;

}


GraphicsClass::GraphicsClass(const GraphicsClass& other)
{
}


GraphicsClass::~GraphicsClass()
{
}


bool GraphicsClass::Initialize(int screenWidth, int screenHeight, HWND hwnd)
{
	bool result;


	// Create the Direct3D object.
	m_D3D = new D3DClass;
	if(!m_D3D)
	{
		return false;
	}

	// Initialize the Direct3D object.
	result = m_D3D->Initialize(screenWidth, screenHeight, VSYNC_ENABLED, hwnd, FULL_SCREEN, SCREEN_DEPTH, SCREEN_NEAR);
	if(!result)
	{
		MessageBox(hwnd, L"Could not initialize Direct3D.", L"Error", MB_OK);
		return false;
	}

	// Create the camera object.
	m_Camera = new CameraClass;
	if(!m_Camera)
	{
		return false;
	}

	// Set the initial position of the camera.
	m_Camera->SetPosition(0.0f, 0.0f, -10.0f);
	
	// Create the model object.
	m_Model = new ModelClass;
	if(!m_Model)
	{
		return false;
	}

	// Initialize the model object.
	result = m_Model->Initialize(m_D3D->GetDevice(), L"../Engine/data/seafloor.dds");
	if(!result)
	{
		MessageBox(hwnd, L"Could not initialize the model object.", L"Error", MB_OK);
		return false;
	}

此處建立並初始化新的光照著色器物件。

	// Create the light shader object.
	m_LightShader = new LightShaderClass;
	if(!m_LightShader)
	{
		return false;
	}

	// Initialize the light shader object.
	result = m_LightShader->Initialize(m_D3D->GetDevice(), hwnd);
	if(!result)
	{
		MessageBox(hwnd, L"Could not initialize the light shader object.", L"Error", MB_OK);
		return false;
	}

此處建立新的光照物件。

	// Create the light object.
	m_Light = new LightClass;
	if(!m_Light)
	{
		return false;
	}

將光照顏色設定為紫色，光照方向設定為指向正 Z 軸方向。

	// Initialize the light object.
	m_Light->SetDiffuseColor(1.0f, 0.0f, 1.0f, 1.0f);
	m_Light->SetDirection(0.0f, 0.0f, 1.0f);

	return true;
}


void GraphicsClass::Shutdown()
{

Shutdown 函式釋放新的光照和光照著色器物件。

	// Release the light object.
	if(m_Light)
	{
		delete m_Light;
		m_Light = 0;
	}

	// Release the light shader object.
	if(m_LightShader)
	{
		m_LightShader->Shutdown();
		delete m_LightShader;
		m_LightShader = 0;
	}

	// Release the model object.
	if(m_Model)
	{
		m_Model->Shutdown();
		delete m_Model;
		m_Model = 0;
	}

	// Release the camera object.
	if(m_Camera)
	{
		delete m_Camera;
		m_Camera = 0;
	}

	// Release the D3D object.
	if(m_D3D)
	{
		m_D3D->Shutdown();
		delete m_D3D;
		m_D3D = 0;
	}

	return;
}


bool GraphicsClass::Frame()
{
	bool result;

我們添加了一個新的靜態變數，用於在每一幀中儲存更新的旋轉值，該值將傳遞到 Render 函式。

	static float rotation = 0.0f;


	// Update the rotation variable each frame.
	rotation += (float)D3DX_PI * 0.01f;
	if(rotation > 360.0f)
	{
		rotation -= 360.0f;
	}

	
	// Render the graphics scene.

	result = Render(rotation);

	if(!result)
	{
		return false;
	}

	return true;
}


bool GraphicsClass::Render(float rotation)
{
	D3DXMATRIX worldMatrix, viewMatrix, projectionMatrix;
	bool result;


	// Clear the buffers to begin the scene.
	m_D3D->BeginScene(0.0f, 0.0f, 0.0f, 1.0f);

	// Generate the view matrix based on the camera's position.
	m_Camera->Render();

	// Get the world, view, and projection matrices from the camera and d3d objects.
	m_Camera->GetViewMatrix(viewMatrix);
	m_D3D->GetWorldMatrix(worldMatrix);
	m_D3D->GetProjectionMatrix(projectionMatrix);

這裡我們根據旋轉值旋轉世界矩陣，這樣當我們使用更新後的世界矩陣渲染三角形時，它就會以旋轉量旋轉三角形。

	// Rotate the world matrix by the rotation value so that the triangle will spin.
	D3DXMatrixRotationY(&worldMatrix, rotation);

	// Put the model vertex and index buffers on the graphics pipeline to prepare them for drawing.
	m_Model->Render(m_D3D->GetDeviceContext());

此處呼叫光照著色器來渲染三角形。新的光照物件用於將漫射光顏色和光照方向傳送到 Render 函式，以便著色器可以訪問這些值。

	// Render the model using the light shader.
	result = m_LightShader->Render(m_D3D->GetDeviceContext(), m_Model->GetIndexCount(), worldMatrix, viewMatrix, projectionMatrix, 
				       m_Model->GetTexture(), m_Light->GetDirection(), m_Light->GetDiffuseColor());
	if(!result)
	{
		return false;
	}

	// Present the rendered scene to the screen.
	m_D3D->EndScene();

	return true;
}

總結

透過對程式碼進行一些修改，我們能夠實現一些基本的定向光照。確保你理解法線向量是如何工作的，以及它們為什麼對於計算多邊形表面的光照很重要。請注意，旋轉三角形的背面不會亮起來，因為我們在 D3DClass 中啟用了背面剔除。

待辦事項練習

1. 重新編譯專案，確保你得到一個被紫色光照亮的旋轉紋理三角形。按 Esc 鍵退出。

2. 在畫素著色器中註釋掉 "color = color * textureColor;"，這樣 shaderTexture 就不會再被使用，你應該會看到沒有紋理的光照效果。

3. 在 GraphicsClass 中的 m_Light->SetDiffuseColor 程式碼行將光照顏色更改為綠色。

4. 將光照方向更改為指向正 X 軸和負 X 軸方向。你可能還想更改旋轉速度。