DirectX/10.0/Direct3D/Alpha Mapping

DirectX 11 中的 Alpha Mapping 是使用纹理的 Alpha 层来确定组合两个纹理时每个像素的混合量的过程。

要开始该过程，您首先要为纹理创建一个 Alpha 层，如下所示

每个像素只是一个 0.0 到 1.0 的浮点范围，指示如何组合两个纹理。例如，如果某个像素的 Alpha 值为 0.3，则将采用基本纹理像素值的 30% 并将其与颜色纹理像素值的 70% 相结合。在本教程中，我们将根据 Alpha 图来组合以下两个纹理

最终结果如下

在本教程中，我将把 Alpha 图分离到它自己的独立纹理上。这使我们能够创建多个 Alpha 图，然后以多种不同的方式组合相同的两个颜色和基本纹理。

本教程中的代码基于之前的教程。

Alphamap.vs

Alpha 图顶点着色器只是从之前的教程中重命名的光照图着色器。

////////////////////////////////////////////////////////////////////////////////
// Filename: alphamap.vs
////////////////////////////////////////////////////////////////////////////////


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


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

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


////////////////////////////////////////////////////////////////////////////////
// Vertex Shader
////////////////////////////////////////////////////////////////////////////////
PixelInputType AlphaMapVertexShader(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;
    
    return output;
}

Alphamap.ps

////////////////////////////////////////////////////////////////////////////////
// Filename: alphamap.ps
////////////////////////////////////////////////////////////////////////////////


/////////////
// GLOBALS //
/////////////

像素着色器的第一个变化是在纹理数组中添加了第三个元素来保存 Alpha 图纹理。

Texture2D shaderTextures[3];
SamplerState SampleType;


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

在 Alpha 图像素着色器中，我们首先从两个颜色纹理和 Alpha 纹理中采样像素。然后，我们将 Alpha 值乘以基本颜色以获得基本纹理的像素值。之后，我们将 Alpha 的逆（1.0 - Alpha）乘以第二个颜色纹理以获得第二个纹理的像素值。然后，我们将两个像素值加在一起并饱和以生成最终的混合像素。

////////////////////////////////////////////////////////////////////////////////
// Pixel Shader
////////////////////////////////////////////////////////////////////////////////
float4 AlphaMapPixelShader(PixelInputType input) : SV_TARGET
{
    float4 color1;
    float4 color2;
    float4 alphaValue;
    float4 blendColor;


    // Get the pixel color from the first texture.
    color1 = shaderTextures[0].Sample(SampleType, input.tex);

    // Get the pixel color from the second texture.
    color2 = shaderTextures[1].Sample(SampleType, input.tex);

    // Get the alpha value from the alpha map texture.
    alphaValue = shaderTextures[2].Sample(SampleType, input.tex);
	
    // Combine the two textures based on the alpha value.
    blendColor = (alphaValue * color1) + ((1.0 - alphaValue) * color2);
    
    // Saturate the final color value.
    blendColor = saturate(blendColor);

    return blendColor;
}

Alphamapshaderclass.h

AlphaMapShaderClass 是从之前的教程中略微修改过的 LightMapShaderClass。

////////////////////////////////////////////////////////////////////////////////
// Filename: alphamapshaderclass.h
////////////////////////////////////////////////////////////////////////////////
#ifndef _ALPHAMAPSHADERCLASS_H_
#define _ALPHAMAPSHADERCLASS_H_


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


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

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

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

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

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

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

#endif

Alphamapshaderclass.cpp

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


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


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


AlphaMapShaderClass::~AlphaMapShaderClass()
{
}


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

第一个变化是现在加载了 alphamap.vs 和 alphamap.ps HLSL 着色器文件。

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

	return true;
}


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

	return;
}


bool AlphaMapShaderClass::Render(ID3D11DeviceContext* deviceContext, int indexCount, D3DXMATRIX worldMatrix,
				 D3DXMATRIX viewMatrix, D3DXMATRIX projectionMatrix, ID3D11ShaderResourceView** textureArray)
{
	bool result;


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

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

	return true;
}


bool AlphaMapShaderClass::InitializeShader(ID3D11Device* device, HWND hwnd, WCHAR* vsFilename, WCHAR* psFilename)
{
	HRESULT result;
	ID3D10Blob* errorMessage;
	ID3D10Blob* vertexShaderBuffer;
	ID3D10Blob* pixelShaderBuffer;
	D3D11_INPUT_ELEMENT_DESC polygonLayout[2];
	unsigned int numElements;
	D3D11_BUFFER_DESC matrixBufferDesc;
	D3D11_SAMPLER_DESC samplerDesc;


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

Alpha 图顶点着色器在此处加载。

	// Compile the vertex shader code.
	result = D3DX11CompileFromFile(vsFilename, NULL, NULL, "AlphaMapVertexShader", "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;
	}

Alpha 图像素着色器在此处加载。

	// Compile the pixel shader code.
	result = D3DX11CompileFromFile(psFilename, NULL, NULL, "AlphaMapPixelShader", "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 vertex 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 stucture 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;

	// 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;

	// Setup the description of the matrix dynamic 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 matrix 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;
	}

	// 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;
	}

	return true;
}


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

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


bool AlphaMapShaderClass::SetShaderParameters(ID3D11DeviceContext* deviceContext, D3DXMATRIX worldMatrix,
					      D3DXMATRIX viewMatrix, D3DXMATRIX projectionMatrix, 
					      ID3D11ShaderResourceView** textureArray)
{
	HRESULT result;
	D3D11_MAPPED_SUBRESOURCE mappedResource;
	MatrixBufferType* dataPtr;
	unsigned int bufferNumber;


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

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

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

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

下一个主要变化是我们现在在着色器中设置三个纹理，而不是之前的教程中的两个。

	// Set shader texture array resource in the pixel shader.
	deviceContext->PSSetShaderResources(0, 3, textureArray);

	return true;
}


void AlphaMapShaderClass::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 triangles.
	deviceContext->DrawIndexed(indexCount, 0, 0);

	return;
}

Texturearrayclass.h

TextureArrayClass 已更改为处理三个纹理，而不是两个。

////////////////////////////////////////////////////////////////////////////////
// Filename: texturearrayclass.h
////////////////////////////////////////////////////////////////////////////////
#ifndef _TEXTUREARRAYCLASS_H_
#define _TEXTUREARRAYCLASS_H_


//////////////
// INCLUDES //
//////////////
#include <d3d11.h>
#include <d3dx11tex.h>


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

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

	ID3D11ShaderResourceView** GetTextureArray();

private:

纹理数组中的元素数量更改为三个。

	ID3D11ShaderResourceView* m_textures[3];
};

#endif

Texturearrayclass.cpp

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

三个纹理在类构造函数中初始化为 null。

TextureArrayClass::TextureArrayClass()
{
	m_textures[0] = 0;
	m_textures[1] = 0;
	m_textures[2] = 0;
}


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


TextureArrayClass::~TextureArrayClass()
{
}

Initialize 函数现在将三个纹理加载到纹理数组中。

bool TextureArrayClass::Initialize(ID3D11Device* device, WCHAR* filename1, WCHAR* filename2, WCHAR* filename3)
{
	HRESULT result;


	// Load the first texture in.
	result = D3DX11CreateShaderResourceViewFromFile(device, filename1, NULL, NULL, &m_textures[0], NULL);
	if(FAILED(result))
	{
		return false;
	}

	// Load the second texture in.
	result = D3DX11CreateShaderResourceViewFromFile(device, filename2, NULL, NULL, &m_textures[1], NULL);
	if(FAILED(result))
	{
		return false;
	}

	// Load the third texture in.
	result = D3DX11CreateShaderResourceViewFromFile(device, filename3, NULL, NULL, &m_textures[2], NULL);
	if(FAILED(result))
	{
		return false;
	}

	return true;
}

Shutdown 现在释放三个纹理。

void TextureArrayClass::Shutdown()
{
	// Release the texture resources.
	if(m_textures[0])
	{
		m_textures[0]->Release();
		m_textures[0] = 0;
	}

	if(m_textures[1])
	{
		m_textures[1]->Release();
		m_textures[1] = 0;
	}

	if(m_textures[2])
	{
		m_textures[2]->Release();
		m_textures[2] = 0;
	}

	return;
}


ID3D11ShaderResourceView** TextureArrayClass::GetTextureArray()
{
	return m_textures;
}

Modelclass.h

ModelClass 已稍微修改，以处理三个纹理，而不是两个。

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


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


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


////////////////////////////////////////////////////////////////////////////////
// Class name: ModelClass
////////////////////////////////////////////////////////////////////////////////
class ModelClass
{
private:
	struct VertexType
	{
		D3DXVECTOR3 position;
		D3DXVECTOR2 texture;
	};

	struct ModelType
	{
		float x, y, z;
		float tu, tv;
		float nx, ny, nz;
	};

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

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

	int GetIndexCount();
	ID3D11ShaderResourceView** GetTextureArray();

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

	bool LoadTextures(ID3D11Device*, WCHAR*, WCHAR*, WCHAR*);
	void ReleaseTextures();

	bool LoadModel(char*);
	void ReleaseModel();

private:
	ID3D11Buffer *m_vertexBuffer, *m_indexBuffer;
	int m_vertexCount, m_indexCount;
	ModelType* m_model;
	TextureArrayClass* m_TextureArray;
};

#endif

Modelclass.cpp

我将只介绍自上一教程以来已更改的功能。

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

Initialize 函数现在以三个纹理名称作为输入。前两个是颜色纹理，第三个是 Alpha 纹理。

bool ModelClass::Initialize(ID3D11Device* device, char* modelFilename, WCHAR* textureFilename1, WCHAR* textureFilename2, 
			    WCHAR* textureFilename3)
{
	bool result;


	// Load in the model data,
	result = LoadModel(modelFilename);
	if(!result)
	{
		return false;
	}

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

LoadTextures 现在以三个纹理名称作为输入。

	// Load the textures for this model.
	result = LoadTextures(device, textureFilename1, textureFilename2, textureFilename3);
	if(!result)
	{
		return false;
	}

	return true;
}

LoadTextures 函数现在以三个纹理文件名作为输入，然后使用三个纹理文件创建并加载纹理数组。再次，前两个纹理是颜色纹理，第三个是 Alpha 纹理。

bool ModelClass::LoadTextures(ID3D11Device* device, WCHAR* filename1, WCHAR* filename2, WCHAR* filename3)
{
	bool result;


	// Create the texture array object.
	m_TextureArray = new TextureArrayClass;
	if(!m_TextureArray)
	{
		return false;
	}

	// Initialize the texture array object.
	result = m_TextureArray->Initialize(device, filename1, filename2, filename3);
	if(!result)
	{
		return false;
	}

	return true;
}

Graphicsclass.h

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


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


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

新的 AlphaMapShaderClass 头文件现在已包含在 GraphicsClass 头文件中。

#include "alphamapshaderclass.h"


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

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

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

我们在此处创建新的 AlphaMapShaderClass 对象。

	AlphaMapShaderClass* m_AlphaMapShader;
};

#endif

Graphicsclass.cpp

我将只介绍自上一教程以来已更改的功能。

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


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

新的 AlphaMapShaderClass 对象在类构造函数中初始化为 null。

	m_AlphaMapShader = 0;
}


bool GraphicsClass::Initialize(int screenWidth, int screenHeight, HWND hwnd)
{
	bool result;
	D3DXMATRIX baseViewMatrix;

		
	// 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;
	}

	// Initialize a base view matrix with the camera for 2D user interface rendering.
	m_Camera->SetPosition(0.0f, 0.0f, -1.0f);
	m_Camera->Render();
	m_Camera->GetViewMatrix(baseViewMatrix);

	// Create the model object.
	m_Model = new ModelClass;
	if(!m_Model)
	{
		return false;
	}

ModelClass 对象使用三个纹理初始化。前两个纹理是颜色纹理。第三个输入纹理是将用于混合前两个纹理的 Alpha 纹理。

	// Initialize the model object.
	result = m_Model->Initialize(m_D3D->GetDevice(), "../Engine/data/square.txt", L"../Engine/data/stone01.dds", 
				     L"../Engine/data/dirt01.dds", L"../Engine/data/alpha01.dds");
	if(!result)
	{
		MessageBox(hwnd, L"Could not initialize the model object.", L"Error", MB_OK);
		return false;
	}

新的 AlphaMapShaderClass 对象在此处创建和初始化。

	// Create the alpha map shader object.
	m_AlphaMapShader = new AlphaMapShaderClass;
	if(!m_AlphaMapShader)
	{
		return false;
	}

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

	return true;
}


void GraphicsClass::Shutdown()
{

新的 AlphaMapShaderClass 对象在此处的 Shutdown 函数中释放。

	// Release the alpha map shader object.
	if(m_AlphaMapShader)
	{
		m_AlphaMapShader->Shutdown();
		delete m_AlphaMapShader;
		m_AlphaMapShader = 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::Render()
{
	D3DXMATRIX worldMatrix, viewMatrix, projectionMatrix, orthoMatrix;


	// 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, projection, and ortho matrices from the camera and D3D objects.
	m_D3D->GetWorldMatrix(worldMatrix);
	m_Camera->GetViewMatrix(viewMatrix);
	m_D3D->GetProjectionMatrix(projectionMatrix);
	m_D3D->GetOrthoMatrix(orthoMatrix);

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

新的 AlphaMapShaderClass 对象用于使用 Alpha 混合渲染模型对象。

	// Render the model using the alpha map shader.
	m_AlphaMapShader->Render(m_D3D->GetDeviceContext(), m_Model->GetIndexCount(), worldMatrix, viewMatrix, projectionMatrix,
				 m_Model->GetTextureArray());

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

	return true;
}

总结

Alpha Mapping 提供了一种简便的方法，可以非常细致地控制如何组合纹理。许多基于地形的应用程序使用它来在非常大的景观上提供不同纹理之间的平滑过渡。

待办事项练习

1. 重新编译并运行程序以查看 Alpha 映射纹理组合。按 Esc 退出。

2. 创建一些您自己的 Alpha 图，并使用它们以不同的方式组合两个纹理。