DirectX 10 教程19：Alpha映射

原文地址：Tutorial 19: Alpha Mapping(http://www.rastertek.com/dx10tut19.html)。

源代码下载：dx10tut19.zip。

Alpha映射指在组合两张纹理时，使用一张alpha贴图确定每个像素的混合权重。

首先需要创建一个如下图所示的alpha贴图：

每个像素的范围在0.0和1.0之间，表示如何组合两张纹理。例如如果一个像素的alpha值为0.3，则取30%的基纹理像素值和70%的颜色纹理像素值进行组合。本教程会组合以下两张纹理：

最终的结果如下图所示：

本教程我们将alpha贴图放置在一张独立的纹理中，这样我们就可以使用不同的alpha贴图组合相同的两张纹理。

本教程的代码基于上一个教程。

Alphamap.fx

alpha map shader只是上一个教程的light map shader的改编版本。

////////////////////////////////////////////////////////////////////////////////
// Filename: alphamap.fx
////////////////////////////////////////////////////////////////////////////////


/////////////
// GLOBALS //
/////////////
matrix worldMatrix;
matrix viewMatrix;
matrix projectionMatrix;

第一个改变是纹理数组包含第三个元素用于保存alpha贴图。

Texture2D shaderTextures[3];


///////////////////
// SAMPLE STATES //
///////////////////
SamplerState SampleType
{
    Filter = MIN_MAG_MIP_LINEAR;
    AddressU = Wrap;
    AddressV = Wrap;
};


//////////////
// 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;
}

主要的变化在像素着色器之中。首先采样三张纹理，然后将alpha值乘以基纹理像素颜色，(1.0 - alpha)乘以第二张纹理像素颜色，最后相加获取最终的像素颜色。

////////////////////////////////////////////////////////////////////////////////
// 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;
}


////////////////////////////////////////////////////////////////////////////////
// Technique
////////////////////////////////////////////////////////////////////////////////
technique10 AlphaMapTechnique
{
    pass pass0
    {
        SetVertexShader(CompileShader(vs_4_0, AlphaMapVertexShader()));
        SetPixelShader(CompileShader(ps_4_0, AlphaMapPixelShader()));
        SetGeometryShader(NULL);
    }
}

Alphamapshaderclass.h

AlphaMapShaderClass只在上一个教程中的LightMapShaderClass上稍加修改。

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


//////////////
// INCLUDES //
//////////////
#include <d3d10.h>
#include <d3dx10.h>
#include <fstream>
using namespace std;


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

	bool Initialize(ID3D10Device*, HWND);
	void Shutdown();
	void Render(ID3D10Device*, int, D3DXMATRIX, D3DXMATRIX, D3DXMATRIX, ID3D10ShaderResourceView**);

private:
	bool InitializeShader(ID3D10Device*, HWND, WCHAR*);
	void ShutdownShader();
	void OutputShaderErrorMessage(ID3D10Blob*, HWND, WCHAR*);

	void SetShaderParameters(D3DXMATRIX, D3DXMATRIX, D3DXMATRIX, ID3D10ShaderResourceView**);
	void RenderShader(ID3D10Device*, int);

private:
	ID3D10Effect* m_effect;
	ID3D10EffectTechnique* m_technique;
	ID3D10InputLayout* m_layout;

	ID3D10EffectMatrixVariable* m_worldMatrixPtr;
	ID3D10EffectMatrixVariable* m_viewMatrixPtr;
	ID3D10EffectMatrixVariable* m_projectionMatrixPtr;

	ID3D10EffectShaderResourceVariable* m_textureArrayPtr;
};

#endif

Alphamapshaderclass.cpp

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


AlphaMapShaderClass::AlphaMapShaderClass()
{
	m_effect = 0;
	m_technique = 0;
	m_layout = 0;

	m_worldMatrixPtr = 0;
	m_viewMatrixPtr = 0;
	m_projectionMatrixPtr = 0;
	
	m_textureArrayPtr = 0;
}


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


AlphaMapShaderClass::~AlphaMapShaderClass()
{
}


bool AlphaMapShaderClass::Initialize(ID3D10Device* device, HWND hwnd)
{
	bool result;

第一个变化在于加载的是alphamap.fx HLSL shader文件。

	// Initialize the shader that will be used to draw the model.
	result = InitializeShader(device, hwnd, L"../Engine/alphamap.fx");
	if(!result)
	{
		return false;
	}

	return true;
}


void AlphaMapShaderClass::Shutdown()
{
	// Shutdown the shader effect.
	ShutdownShader();

	return;
}


void AlphaMapShaderClass::Render(ID3D10Device* device, int indexCount, D3DXMATRIX worldMatrix, D3DXMATRIX viewMatrix,
								 D3DXMATRIX projectionMatrix, ID3D10ShaderResourceView** textureArray)
{
	// Set the shader parameters that it will use for rendering.
	SetShaderParameters(worldMatrix, viewMatrix, projectionMatrix, textureArray);

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

	return;
}


bool AlphaMapShaderClass::InitializeShader(ID3D10Device* device, HWND hwnd, WCHAR* filename)
{
	HRESULT result;
	ID3D10Blob* errorMessage;
	D3D10_INPUT_ELEMENT_DESC polygonLayout[2];
	unsigned int numElements;
    D3D10_PASS_DESC passDesc;


	// Initialize the error message.
	errorMessage = 0;

	// Load the shader in from the file.
	result = D3DX10CreateEffectFromFile(filename, NULL, NULL, "fx_4_0", D3D10_SHADER_ENABLE_STRICTNESS, 0, 
										device, NULL, NULL, &m_effect, &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, filename);
		}
		// If there was  nothing in the error message then it simply could not find the shader file itself.
		else
		{
			MessageBox(hwnd, filename, L"Missing Shader File", MB_OK);
		}

		return false;
	}

Technique名称变为AlphaMapTechnique。

	// Get a pointer to the technique inside the shader.
	m_technique = m_effect->GetTechniqueByName("AlphaMapTechnique");
	if(!m_technique)
	{
		return false;
	}

	// Now setup the layout of the data that goes into the shader.
	// 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 = D3D10_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 = D3D10_APPEND_ALIGNED_ELEMENT;
	polygonLayout[1].InputSlotClass = D3D10_INPUT_PER_VERTEX_DATA;
	polygonLayout[1].InstanceDataStepRate = 0;

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

	// Get the description of the first pass described in the shader technique.
    m_technique->GetPassByIndex(0)->GetDesc(&passDesc);

	// Create the input layout.
    result = device->CreateInputLayout(polygonLayout, numElements, passDesc.pIAInputSignature, passDesc.IAInputSignatureSize, 
									   &m_layout);
	if(FAILED(result))
	{
		return false;
	}

	// Get pointers to the three matrices inside the shader so we can update them from this class.
    m_worldMatrixPtr = m_effect->GetVariableByName("worldMatrix")->AsMatrix();
	m_viewMatrixPtr = m_effect->GetVariableByName("viewMatrix")->AsMatrix();
    m_projectionMatrixPtr = m_effect->GetVariableByName("projectionMatrix")->AsMatrix();

	// Get pointer to the texture array resource inside the shader.
	m_textureArrayPtr = m_effect->GetVariableByName("shaderTextures")->AsShaderResource();

	return true;
}


void AlphaMapShaderClass::ShutdownShader()
{
	// Release the pointer to the texture in the shader file.
	m_textureArrayPtr = 0;

	// Release the pointers to the matrices inside the shader.
	m_worldMatrixPtr = 0;
	m_viewMatrixPtr = 0;
	m_projectionMatrixPtr = 0;

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

	// Release the pointer to the shader technique.
	m_technique = 0;

	// Release the pointer to the shader.
	if(m_effect)
	{
		m_effect->Release();
		m_effect = 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 << compileErrors[i];
	}

	// Close the file.
	fout.close();

	// Release the error message.
	errorMessage->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;
}


void AlphaMapShaderClass::SetShaderParameters(D3DXMATRIX worldMatrix, D3DXMATRIX viewMatrix, D3DXMATRIX projectionMatrix,
											  ID3D10ShaderResourceView** textureArray)
{
	// Set the world matrix variable inside the shader.
    m_worldMatrixPtr->SetMatrix((float*)&worldMatrix);

	// Set the view matrix variable inside the shader.
	m_viewMatrixPtr->SetMatrix((float*)&viewMatrix);

	// Set the projection matrix variable inside the shader.
    m_projectionMatrixPtr->SetMatrix((float*)&projectionMatrix);

第三个变化是设置的是三张纹理而不是上一个教程的两个。

	// Bind the texture array.
	m_textureArrayPtr->SetResourceArray(textureArray, 0, 3);

	return;
}


void AlphaMapShaderClass::RenderShader(ID3D10Device* device, int indexCount)
{
    D3D10_TECHNIQUE_DESC techniqueDesc;
	unsigned int i;
	

	// Set the input layout.
	device->IASetInputLayout(m_layout);

	// Get the description structure of the technique from inside the shader so it can be used for rendering.
    m_technique->GetDesc(&techniqueDesc);

    // Go through each pass in the technique (should be just one currently) and render the triangles.
	for(i=0; i<techniqueDesc.Passes; ++i)
    {
        m_technique->GetPassByIndex(i)->Apply(0);
        device->DrawIndexed(indexCount, 0, 0);
    }

	return;
}

Texturearrayclass.h

TextureArrayClass修改为可以处理三张纹理。

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


//////////////
// INCLUDES //
//////////////
#include <d3d10.h>
#include <d3dx10.h>


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

	bool Initialize(ID3D10Device*, WCHAR*, WCHAR*, WCHAR*);
	void Shutdown();

	ID3D10ShaderResourceView** GetTextureArray();

private:

纹理数组的大小修改为3。

	ID3D10ShaderResourceView* m_textures[3];
};

#endif

Texturearrayclass.cpp

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

构造函数中将三张纹理初始化为null。

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


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


TextureArrayClass::~TextureArrayClass()
{
}

在Initialize方法中将三张纹理加载到纹理数组中。

bool TextureArrayClass::Initialize(ID3D10Device* device, WCHAR* filename1, WCHAR* filename2, WCHAR* filename3)
{
	HRESULT result;


	// Load the first texture in.
	result = D3DX10CreateShaderResourceViewFromFile(device, filename1, NULL, NULL, &m_textures[0], NULL);
	if(FAILED(result))
	{
		return false;
	}

	// Load the second texture in.
	result = D3DX10CreateShaderResourceViewFromFile(device, filename2, NULL, NULL, &m_textures[1], NULL);
	if(FAILED(result))
	{
		return false;
	}

	// Load the third texture in.
	result = D3DX10CreateShaderResourceViewFromFile(device, filename3, NULL, NULL, &m_textures[2], NULL);
	if(FAILED(result))
	{
		return false;
	}

	return true;
}

Shutdown方法释放三张纹理。

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;
}


ID3D10ShaderResourceView** TextureArrayClass::GetTextureArray()
{
	return m_textures;
}

Modelclass.h

ModelClass修改为可以处理三张纹理而不是上一个教程的两张。

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


//////////////
// INCLUDES //
//////////////
#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(ID3D10Device*, char*, WCHAR*, WCHAR*, WCHAR*);
	void Shutdown();
	void Render(ID3D10Device*);

	int GetIndexCount();
	ID3D10ShaderResourceView** GetTextureArray();

private:
	bool InitializeBuffers(ID3D10Device*);
	void ShutdownBuffers();
	void RenderBuffers(ID3D10Device*);

	bool LoadTextures(ID3D10Device*, WCHAR*, WCHAR*, WCHAR*);
	void ReleaseTextures();

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

private:
	ID3D10Buffer *m_vertexBuffer, *m_indexBuffer;
	int m_vertexCount, m_indexCount;
	ModelType* m_model;
	TextureArrayClass* m_TextureArray;
};

#endif

Modelclass.cpp

下面的代码只包含与上一个教程不同的部分。

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

Initialize方法的参数为三张纹理文件的名称，前两个为颜色纹理，第三个为alpha贴图纹理。

bool ModelClass::Initialize(ID3D10Device* 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 buffer that hold the geometry for the triangle.
	result = InitializeBuffers(device);
	if(!result)
	{
		return false;
	}

LoadTextures的参数现在变为三张纹理的文件名称。

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

	return true;
}

LoadTextures方法的参数为三张纹理文明的名称，然后创建并加载纹理数组。

bool ModelClass::LoadTextures(ID3D10Device* 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头文件包含在GraphicsClass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;

下面的代码创建新的AlphaMapShaderClass对象。

	AlphaMapShaderClass* m_AlphaMapShader;
};

#endif

Graphicsclass.cpp

下面的代码只包含与上一个教程不同的部分。

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


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

在构造函数中将新AlphaMapShaderClass对象初始化为null。

	m_AlphaMapShader = 0;
}


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


GraphicsClass::~GraphicsClass()
{
}


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对象初始化三张纹理。

	// 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;
	}

下面的代码创建并初始化AlphaMapShaderClass对象。

	// 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()
{

释放AlphaMapShaderClass对象。

	// 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 Direct3D object.
	if(m_D3D)
	{
		m_D3D->Shutdown();
		delete m_D3D;
		m_D3D = 0;
	}

	return;
}


bool GraphicsClass::Frame()
{
	// Set the position of the camera.
	m_Camera->SetPosition(0.0f, 0.0f, -5.0f);

	return true;
}


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->GetDevice());

新的AlphaMapShaderClass对象用于使用alpha混合绘制模型对象。

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

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

	return true;
}

总结

Alpha映射提供了一个控制组合纹理效果的简易方法，许多基于地形的程序都会使用这个方法实现纹理间的平滑过渡。

练习

1．编译并允许程序，你可以看到经过alpha映射过的纹理组合，按escape键退出。

2．制作你自己的alpha贴图并用它组合两张纹理。

发布时间：2012/8/3 下午10:36:34  阅读次数：7366