计算机图形学编程试8MFC明暗处理实现

计算机图形学编程试8MFC明暗处理实现

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计算机图形学编程练习8：MFC+明暗处理实现

MFC与OpenGL集成

在Windows下编程，利用MFC是一个非常便捷的方法。本次练习的主要目的，是希望同学们在MFC应用程序框架下进行OpenGL编程。为此，需要对MFC生成的应用程序进行适当的初始化，关于这方面的内容详见：

[1] Crain, Dennis. "Windows NT OpenGL: Getting Started." April 1994. (MSDN Library, Technical Articles)

[2] Rogerson, Dale. "OpenGL I: Quick Start.". December 1994. (MSDN Library, Technical Articles)

[3] D. Shreiner and The Khronos OpenGL ARB Working Group. OpenGL Programming Guide: The Official Guide to Learning OpenGL, Versions 3.0 and 3.1, 7th Ed., 2009. (附录D)

从设计目标来说，OpenGL是流水线结构(streamlined)、硬件无关(hardware-independent)、跨平台的3D图形编程API。但是，在实际应用时，OpenGL的具体实现是与操作系统以及图形硬件相关的。为此，操作系统需要提供像素格式(pixel format)与绘制上下文管理函数(rendering context managnment functions)。Windows操作系统提供了通用图形设备接口(generic graphics device interface, GDI)以及设备驱动实现。为了使OpenGL命令得到正确的执行，需要调用WGL函数，具体的步骤如下：

Step 1: 添加成员变量

在CView类(利用AppWizard生成)中添加如下成员变量：

// OpenGL Windows specification

HDC m_hDC; // Device Context

HGLRC m_hGLRC; // Rendering Context

CPalette m_cGLLP; // Logical Palette

Step 2: 设置像素格式

创建CView类的WM_CREATE的消息响应函数，进行像素格式的设置，例如：

int COpenGLRenderView::OnCreate(LPCREATESTRUCT lpCreateStruct)

{

if (CView::OnCreate(lpCreateStruct) == -1)

return -1;

// TODO: Add your specialized creation code here

int nPixelFormat; // Pixel format index

HWND hWnd = GetSafeHwnd(); // Get the window's handle

m_hDC = ::GetDC(hWnd); // Get the Device context

static PIXELFORMATDESCRIPTOR pfd = {

sizeof(PIXELFORMATDESCRIPTOR), // Size of this structure

1, // Version of this structure

PFD_DRAW_TO_WINDOW | // Draw to Window (not to bitmap)

PFD_SUPPORT_OPENGL | // Support OpenGL calls in window

PFD_DOUBLEBUFFER, // Double buffered mode

PFD_TYPE_RGBA, // RGBA Color mode

24, // Want 24bit color

0,0,0,0,0,0, // Not used to select mode

0,0, // Not used to select mode

0,0,0,0,0, // Not used to select mode

32, // Size of depth buffer

0, // Not used to select mode

0, // Not used to select mode

PFD_MAIN_PLANE, // Draw in main plane

0, // Not used to select mode

0,0,0 }; // Not used to select mode

// Choose a pixel format that best matches that described in pfd

nPixelFormat = ChoosePixelFormat(m_hDC, &pfd);

// Set the pixel format for the device context

VERIFY(SetPixelFormat(m_hDC, nPixelFormat, &pfd));

// Create the rendering context

m_hGLRC = wglCreateContext(m_hDC);

// Create the palette if needed

InitializePalette();

// Make the rendering context current, perform initialization, then deselect it VERIFY(wglMakeCurrent(m_hDC, m_hGLRC));

GLSetupDef(m_hDC);

wglMakeCurrent(NULL, NULL);

return 0;

}

上述步骤的具体含义参看参考文献[1-3].

Step 3: 创建绘制上下文

该步骤在Step 2中已完成，具体的就是：

m_hGLRC = wglCreateContext(m_hDC);

Step 4: 设置调色板

创建CView类的一个成员函数，进行调色板的设置，例如：

void CTriangularPatchView::InitializePalette(void)

{

PIXELFORMATDESCRIPTOR pfd; // Pixel Format Descriptor

LOGPALETTE *pPal; // Pointer to memory for logical palette

int nPixelFormat; // Pixel format index

int nColors; // Number of entries in palette

int i; // Counting variable

BYTE RedRange,GreenRange,BlueRange;

// Range for each color entry (7,7,and 3)

// Get the pixel format index and retrieve the pixel format description nPixelFormat = GetPixelFormat(m_hDC);

DescribePixelFormat(m_hDC, nPixelFormat, sizeof(PIXELFORMATDESCRIPTOR), &pfd);

// Does this pixel format require a palette? If not, do not create a

// palette and just return NULL

if (!(pfd.dwFlags & PFD_NEED_PALETTE))

return;

// Number of entries in palette. 8 bits yeilds 256 entries

nColors = 1 << https://www.360docs.net/doc/5d8142101.html,olorBits;

// Allocate space for a logical palette structure plus all the palette entries pPal = (LOGPALETTE*)malloc(sizeof(LOGPALETTE) +nColors*sizeof(PALETTEENTRY));

// Fill in palette header

pPal->palVersion = 0x300; // Windows 3.0

pPal->palNumEntries = nColors; // table size

// Build mask of all 1's. This creates a number represented by having

// the low order x bits set, where x = pfd.cRedBits, pfd.cGreenBits, and

// pfd.cBlueBits.

RedRange = (1 << pfd.cRedBits) -1;

GreenRange = (1 << pfd.cGreenBits) - 1;

BlueRange = (1 << pfd.cBlueBits) -1;

// Loop through all the palette entries

for (i = 0; i < nColors; i++)

{

// Fill in the 8-bit equivalents for each component

pPal->palPalEntry[i].peRed = (i >> pfd.cRedShift) & RedRange;

pPal->palPalEntry[i].peRed = (unsigned char)(

(double) pPal->palPalEntry[i].peRed * 255.0 / RedRange);

pPal->palPalEntry[i].peGreen = (i >> pfd.cGreenShift) & GreenRange;

pPal->palPalEntry[i].peGreen = (unsigned char)(

(double)pPal->palPalEntry[i].peGreen * 255.0 / GreenRange);

pPal->palPalEntry[i].peBlue = (i >> pfd.cBlueShift) & BlueRange;

pPal->palPalEntry[i].peBlue = (unsigned char)(

(double)pPal->palPalEntry[i].peBlue * 255.0 / BlueRange);

pPal->palPalEntry[i].peFlags = (unsigned char) NULL;

}

// Create the palette

m_cGLLP.CreatePalette(pPal);

// Go ahead and select and realize the palette for this device context

SelectPalette(m_hDC,(HPALETTE)m_cGLLP,FALSE);

RealizePalette(m_hDC);

// Free the memory used for the logical palette structure

free(pPal);

}

至此，已经可以调用OpenGL函数了，一定要记住：OpenGL命令只在获取了正确的绘制上下文后才能正确执行，即

wglMakeCurrent(m_hDC, m_hGLRC);

// issue OpenGL commands

…..

wglMakeCurrent(m_hDC, NULL);

Step 5: 重载OnEraseBkgnd函数

创建CView类的WM_ERASEBKGND的消息响应函数，防止Windows进行额外的背景清除操作，例如：BOOL COpenGLRenderView::OnEraseBkgnd(CDC* pDC)

{

// TODO: Add your message handler code here and/or call default

return FALSE;

}

Step 6: 设置OpenGL的基本参数(可选)

在CView类中添加头文件：

#include

#include

#include

以及成员函数：

void GLSetupDef(void *pData);

创建CView类的一个成员函数，进行OpenGL的基本参数的设置，例如：

void COpenGLRenderView::GLSetupDef(void *pData)

{

// set up clear color

glClearColor(1.0f, 1.0f, 1.0f, 1.0f);

// set up lighting

GLfloat light_position0[4] = {52.0f, 16.0f, 50.0f, 0.0f}; GLfloat light_position1[4] = {26.0f, 48.0f, 50.0f, 0.0f}; GLfloat light_position2[4] = {-16.0f, 52.0f, 50.0f, 0.0f};

GLfloat direction0[3] = {-52.0f, -16.0f, -50.0f};

GLfloat direction1[3] = {-26.0f, -48.0f, -50.0f};

GLfloat direction2[3] = {16.0f, -52.0f, -50.0f};

GLfloat color0[4] = {1.0f, 0.0f, 0.0f, 1.0f};

GLfloat color1[4] = {0.0f, 1.0f, 0.0f, 1.0f};

GLfloat color2[4] = {0.0f, 0.0f, 1.0f, 1.0f};

glLightfv(GL_LIGHT0, GL_POSITION, light_position0); glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, direction0); glLightfv(GL_LIGHT0, GL_DIFFUSE, color0);

glLightfv(GL_LIGHT0, GL_SPECULAR, color0);

glLightfv(GL_LIGHT1, GL_POSITION, light_position1); glLightfv(GL_LIGHT1, GL_SPOT_DIRECTION, direction1); glLightfv(GL_LIGHT1, GL_DIFFUSE, color1);

glLightfv(GL_LIGHT1, GL_SPECULAR, color1);

glLightfv(GL_LIGHT2, GL_POSITION, light_position2); glLightfv(GL_LIGHT2, GL_SPOT_DIRECTION, direction2); glLightfv(GL_LIGHT2, GL_DIFFUSE, color2);

glLightfv(GL_LIGHT2, GL_SPECULAR, color2);

glEnable(GL_LIGHTING);

glEnable(GL_LIGHT0);

glEnable(GL_LIGHT1);

glEnable(GL_LIGHT2);

// set up materials

GLfloat ambient[4] = {0.3f, 0.3f, 0.3f, 0.5f};

GLfloat material_ambient[4] = {0.0f, 0.0f, 0.0f, 0.0f}; GLfloat material_diffuse[4] = {1.0f, 1.0f, 1.0f, 0.3f}; GLfloat material_specular[4] = {0.5f, 0.5f, 0.5f, 0.5f}; GLfloat material_shininess = 51.2f;

glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambient);

glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, material_specular);

glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, material_diffuse);

glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, material_ambient);

glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, material_shininess);

// enable depth test

glDepthFunc(GL_LESS);

glEnable(GL_DEPTH_TEST);

// enable cull face

// glCullFace(GL_BACK);

// glEnable(GL_CULL_FACE);

// set up point size and line width

glPointSize(1.0);

glLineWidth(1.0);

// set up point, line, polygon anti-aliasing mode

// glEnable(GL_POINT_SMOOTH);

// glHint(GL_POINT_SMOOTH_HINT, GL_NICEST);

// glEnable(GL_LINE_SMOOTH);

// glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);

glEnable(GL_POLYGON_SMOOTH);

glHint(GL_POLYGON_SMOOTH_HINT, GL_NICEST);

// set up the direction of front face

glFrontFace(GL_CCW);

// glPolygonMode(GL_BACK, GL_LINE);

}

Step 7: 设置绘制模式、重载OnSize函数、鼠标响应函数处理等(可选) 略，参见计算机图形学编程练习6及示例代码。

作业要求

●本次练习的主要学习目标：

?学习使用MFC编程：像素格式、调色板、绘制上下文；

?学习OpenGL编程：光照模型;

●在计算机图形学编程练习6的基础上，实现本次作业的具体要求：

?将程序从GLUT框架移植到MFC框架；

?给点光源设置属性，实现聚光灯的效果；

?给正十二面体设置材质(具体值不限)，实现明暗处理；

下面是一些常见材质属性，同学们可以依据此表设置材质：