DirectX 10 教程26:透明

原文地址:Tutorial 26: Transparency(http://www.rastertek.com/dx10tut26.html)。

源代码下载:dx10tut26.zip

Transparency效果可以让一张带纹理的对象呈现透明效果。

例如下列一张纹理:

源纹理

我们可以让此纹理半透明显示在另一张纹理上面,获得如下图所示的效果:

透明效果

透明是使用alpha混合实现的。任意像素的alpha分量用于确定像素的透明程度。例如,一个像素的alpha值为0.5,则它会以半透明显示。许多纹理都有一个alpha分量,修改这个分量可以让纹理某些部分透明,某些部分不透明。

要让alpha值起作用,你必须首先在shader中打开alpha混合并设置混合方程。本教程使用的混合状态如下所示:

BlendState AlphaBlendingOn { BlendEnable[0] = TRUE; DestBlend = INV_SRC_ALPHA; SrcBlend = SRC_ALPHA; };

DestBlend用于目标颜色,它是该像素已经存在的颜色。我们使用的混合方程中将目标颜色设置为INV_SRC_ALPHA,即取源颜色的反相,即用1减去源颜色的alpha值。例如,如果源的alpha为0.3,则目标的alpha为0.7,这会将70%的目标像素颜色组合到最终颜色中。

SrcBlend用于源像素颜色,即本教程中输入的纹理颜色。混合方程用的是SRC_ALPHA,即源颜色乘以自己的alpha值。

源颜色和目标颜色值会叠加在一起生成最终的输出颜色。

框架

框架中新添了一个名为TransparentShaderClass的新类,这个类类似于TextureShaderClass,只不过多了一个alpha混合值。

框架

Transparent.fx

////////////////////////////////////////////////////////////////////////////////
// Filename: transparent.fx
////////////////////////////////////////////////////////////////////////////////


/////////////
// GLOBALS //
/////////////
matrix worldMatrix;
matrix viewMatrix;
matrix projectionMatrix;
Texture2D shaderTexture;

新添的变量blendAmount表示纹理的透明程度。

float blendAmount;


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

新添的alpha混合状态用来实现透明效果。

/////////////////////
// BLENDING STATES //
/////////////////////
BlendState AlphaBlendingOn
{
    BlendEnable[0] = TRUE;
    DestBlend = INV_SRC_ALPHA;
    SrcBlend = SRC_ALPHA;
};


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

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


////////////////////////////////////////////////////////////////////////////////
// Vertex Shader
////////////////////////////////////////////////////////////////////////////////
PixelInputType TransparentVertexShader(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;
}


////////////////////////////////////////////////////////////////////////////////
// Pixel Shader
////////////////////////////////////////////////////////////////////////////////
float4 TransparentPixelShader(PixelInputType input) : SV_Target
{
	float4 color;
	
	
	// Sample the texture pixel at this location.
	color = shaderTexture.Sample(SampleType, input.tex);

我们使用blendAmount变量设置纹理的透明程度,将像素的alpha值设置为这个变量,当绘制时就会使用alpha值和混合状态创建透明效果。

	// Set the alpha value of this pixel to the blending amount to create the alpha blending effect.
	color.a = blendAmount;

	return color;
}

在technique中使用SetBlendState开启混合状态。注意这个混合状态会一直开启直到在关闭为止,因此使用其他shaer前需要关闭这个状态。

////////////////////////////////////////////////////////////////////////////////
// Technique
////////////////////////////////////////////////////////////////////////////////
technique10 TransparentTechnique
{
    pass pass0
    {
	    SetBlendState(AlphaBlendingOn, float4(0.0f, 0.0f, 0.0f, 0.0f), 0xFFFFFFFF);
        SetVertexShader(CompileShader(vs_4_0, TransparentVertexShader()));
        SetPixelShader(CompileShader(ps_4_0, TransparentPixelShader()));
        SetGeometryShader(NULL);
    }
}

Transparentshaderclass.h

TransparentShaderClass只是TextureShaderClass的改编版本,只是添加了处理透明的代码。

////////////////////////////////////////////////////////////////////////////////
// Filename: transparentshaderclass.h
////////////////////////////////////////////////////////////////////////////////
#ifndef _TRANSPARENTSHADERCLASS_H_
#define _TRANSPARENTSHADERCLASS_H_


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


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

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

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

	void SetShaderParameters(D3DXMATRIX, D3DXMATRIX, D3DXMATRIX, ID3D10ShaderResourceView*, float);
	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_texturePtr;

新添一个指向shader中blendAmount变量的指针。

	ID3D10EffectScalarVariable* m_blendAmountPtr;
};

#endif

Transparentshaderclass.cpp

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


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

	m_worldMatrixPtr = 0;
	m_viewMatrixPtr = 0;
	m_projectionMatrixPtr = 0;
	m_texturePtr = 0;

在类构造函数中将blend amount指针设置为null。

	m_blendAmountPtr = 0;
}


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


TransparentShaderClass::~TransparentShaderClass()
{
}


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

加载transparent HLSL shader文件。

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

	return true;
}


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

	return;
}

Render方法中新添了一个类型为float的blend参数,它设置了纹理的透明程度。

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

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

	return;
}


bool TransparentShaderClass::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的名称修改为TransparentTechnique。

	// Get a pointer to the technique inside the shader.
	m_technique = m_effect->GetTechniqueByName("TransparentTechnique");
	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 resource inside the shader.
	m_texturePtr = m_effect->GetVariableByName("shaderTexture")->AsShaderResource();

获取对应shader中的blendAmount变量的指针。

	// Get a pointer to the blend amount variable inside the shader.
 	m_blendAmountPtr = m_effect->GetVariableByName("blendAmount")->AsScalar();

	return true;
}


void TransparentShaderClass::ShutdownShader()
{

在ShutdownShader方法中释放blendAmount指针。

	// Release the pointer to the blend amount in the shader file.
	m_blendAmountPtr = 0;

	// Release the pointer to the texture in the shader file.
	m_texturePtr = 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 TransparentShaderClass::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 TransparentShaderClass::SetShaderParameters(D3DXMATRIX worldMatrix, D3DXMATRIX viewMatrix, D3DXMATRIX projectionMatrix,
												 ID3D10ShaderResourceView* texture, float blend)
{
	// 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);

	// Bind the texture.
	m_texturePtr->SetResource(texture);

设置shader中的blendAmount的值。

	// Set the blend amount variable inside the shader.
	m_blendAmountPtr->SetFloat(blend);

	return;
}


void TransparentShaderClass::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;
}

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"
#include "textureshaderclass.h"
#include "transparentshaderclass.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;

创建两个模型。

	ModelClass* m_Model1;
	ModelClass* m_Model2;
	TextureShaderClass* m_TextureShader;

创建TransparentShaderClass对象。

	TransparentShaderClass* m_TransparentShader;
};

#endif

Graphicsclass.cpp

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

在构造函数中声明两个模型和TransparentShaderClass。

GraphicsClass::GraphicsClass()
{
	m_D3D = 0;
	m_Camera = 0;
	m_Model1 = 0;
	m_Model2 = 0;
	m_TextureShader = 0;
	m_TransparentShader = 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;
	}

创建并初始化第一个模型,它是一个纹理为dirt01.dds的正方形。

	// Create the first model object.
	m_Model1 = new ModelClass;
	if(!m_Model1)
	{
		return false;
	}

	// Initialize the first model object.
	result = m_Model1->Initialize(m_D3D->GetDevice(), L"../Engine/data/dirt01.dds", "../Engine/data/square.txt");
	if(!result)
	{
		MessageBox(hwnd, L"Could not initialize the first model object.", L"Error", MB_OK);
		return false;
	}

创建并初始化第二个模型,它是一个纹理为stone01.dds的正方形。

	// Create the second model object.
	m_Model2 = new ModelClass;
	if(!m_Model2)
	{
		return false;
	}

	// Initialize the second model object.
	result = m_Model2->Initialize(m_D3D->GetDevice(), L"../Engine/data/stone01.dds", "../Engine/data/square.txt");
	if(!result)
	{
		MessageBox(hwnd, L"Could not initialize the second model object.", L"Error", MB_OK);
		return false;
	}

	// Create the texture shader object.
	m_TextureShader = new TextureShaderClass;
	if(!m_TextureShader)
	{
		return false;
	}

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

创建并初始化TransparentShaderClass对象。

	// Create the transparent shader object.
	m_TransparentShader = new TransparentShaderClass;
	if(!m_TransparentShader)
	{
		return false;
	}

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

	return true;
}

在Shutdown方法中释放TransparentShaderClass对象和两个模型。

void GraphicsClass::Shutdown()
{
	// Release the transparent shader object.
	if(m_TransparentShader)
	{
		m_TransparentShader->Shutdown();
		delete m_TransparentShader;
		m_TransparentShader = 0;
	}

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

	// Release the second model object.
	if(m_Model2)
	{
		m_Model2->Shutdown();
		delete m_Model2;
		m_Model2 = 0;
	}

	// Release the first model object.
	if(m_Model1)
	{
		m_Model1->Shutdown();
		delete m_Model1;
		m_Model1 = 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;
    float blendAmount;

设置blend变量,这个变量会被发送到transparent shader中。

	// Set the blending amount to 50%.
	blendAmount = 0.5f;

	// Clear the scene to the color of the fog.
	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_D3D->GetWorldMatrix(worldMatrix);
	m_Camera->GetViewMatrix(viewMatrix);
	m_D3D->GetProjectionMatrix(projectionMatrix);

在屏幕中央绘制第一个正方形,使用的是常规的texture shader。

	// Put the model vertex and index buffers on the graphics pipeline to prepare them for drawing.
	m_Model1->Render(m_D3D->GetDevice());

	// Render the model using the texture shader.
	m_TextureShader->Render(m_D3D->GetDevice(), m_Model1->GetIndexCount(), worldMatrix, viewMatrix, projectionMatrix,
							m_Model1->GetTexture());

在偏右的地方绘制第二个正方形,位于第一个正方形之上。使用的是新的TransparentShaderClass对象,输入的参数为blendAmount,这样就绘制了一个透明的石头纹理的正方形。

	// Translate to the right by one unit and towards the camera by one unit.
	D3DXMatrixTranslation(&worldMatrix, 1.0f, 0.0f, -1.0f);

	// Put the second square model on the graphics pipeline.
	m_Model2->Render(m_D3D->GetDevice());

	// Render the second square model with the stone texture and use the 50% blending amount for transparency.
	m_TransparentShader->Render(m_D3D->GetDevice(), m_Model2->GetIndexCount(), worldMatrix, viewMatrix, projectionMatrix,
								m_Model2->GetTexture(), blendAmount);

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

	return true;
}

总结

使用透明效果就可以让纹理和模型透明,并可以基于它实现许多不同的效果。

练习

1.编译并运行程序,按Escape键退出。

2.改变GraphicsRender方法中的blendAmount的值观察透明效果的差异。

文件下载(已下载 889 次)

发布时间:2012/8/27 22:48:46  阅读次数:7433

2006 - 2024,推荐分辨率1024*768以上,推荐浏览器Chrome、Edge等现代浏览器,截止2021年12月5日的访问次数:1872万9823 站长邮箱

沪ICP备18037240号-1

沪公网安备 31011002002865号