在MFC中打印OpenGL

3D图形学基本概念PerspectivePerspective refers to the angles between the lines that lend the illusion of three dimensions.Colors and ShadingMoving beyond line drawing, we need to add color to create a solid object. Shading refers to the way the color is applied to the polygon. Shading can be of two types in OpenGL - Flat or Smooth.Lights and ShadowsPlain solid color doesn’t offer enough realism. By applying Lighting effects we can make objects appear as they would in reality depending on their material properties and the lighting parameters. Adding a shadow further increases realism.Texture MappingWith Texture Mapping we can have wood grains, cloth textures, brick like textures etc instead of plain materials. This technique of applying an image to the surface of a polygon is called Texture Mapping. The image we use is called the Texture and the individual elements of the texture are called Texels.FogFog is an atmospheric effect that adds haziness to objects in a scene depending on how far the objects are from the viewer.Blending and TransparencyBlending is the combination of colors of objects on the screen. This effect can be used for a variety of purposes. By varying the amount each object is blended with the scene we can make objects look transparent.Anti-AliasingAliasing is an effect that is visible on screen due to the fact that an image consists of discrete pixels. By carefully blending the lines with the background color we can eliminate jagged edges and give them a smooth appearance. This blending technique is called anti-aliasing.第一个OpenGL程序复制代码//Simple.cpp - First OpenGL Program#include <windows.h> //Required for every Windows Program#include <gl\glut.h> //Required for using the GLUT library//Perform OpenGL Initialization herevoid SetupRC(){//Set the background clearing color to blueglClearColor(0.0f,0.0f,1.0f,1.0f);//设置背景色为蓝色}//The drawing callback functionvoid RenderScene(){//Clear the color bufferglClear(GL_COLOR_BUFFER_BIT);//Flush the rendering pipelineglFlush();}void main(){//Choose the display mode settingsglutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);//初始化显示模式(单缓冲,RGB)//Create the WindowglutCreateWindow("Simple");//创建窗口//Set the RenderScsne function as the display callbackglutDisplayFunc(RenderScene);//绘制回调函数，当窗口需要绘制时，GLUT会调用此函数//Initialize OpenGLSetupRC();//初始化OpenGL//Start the GLUT frameworkglutMainLoop();//开始消息循环}WGL – Windows的OpenGL扩展层The WGL extension consists of a set of functions (wglCreateContext, wglDeleteContext etc.) and structures (such as PIXELFORMATDESCRIPTOR, GLYPHMETRICSFLOAT) etc. Thus every OpenGL implementation has a platform-specific portion which has to be set up and used according to the particular platform.设备上下文The Windows Graphical Device Interface (GDI) is capable of drawing to screen, to memory, to printers or to any other device that provides a GDI interface layer and that can process GDI calls. GDI accomplishes this by a rendering handle to the currently selected device, which is called the device context, or DC.绘制上下文A rendering context is the OpenGL equivalent of the GDI DC. All OpenGL calls are rendered to the device through a RC. The rendering context maintains OpenGL state variables such as current background color, current color etc. just as the DC maintains GDI state variables such as current pen, current brush etc.像素格式Pixel formats are the translation layer between OpenGL calls and the rendering operation that Windows performs.举个例子，若像素格式只支持很少一部分颜色值，则OpenGL在用RGB值(128,120,135)绘制一个像素时，就可能使用转换后的值(128,128,128)来绘制.The pixel format selected essentially describes such things as how colors are displayed, depth of field resolution and what additional capabilities are supported by the rendering context created.第一个基于MFC的OpenGL应用程开发环境：VC6.01，首先下载需要的GLUT头文件,DLL和Lib文件，下载链接: glutdlls37beta.zip (149 kilobytes),解压缩后把gltu.h放到"VC98/Include/GL"下，把glut.lib和glut32.lib放到"VC9/Lib" 下，glut32.dll和glut.dll放到你创建的应用程序的运行目录下2，创建一个MFC SDI应用程序，在项目属性中加入所需要链接的库文件1，在stdafx.h中加入下列语句：//OpenGL Headers#include <gl/gl.h>#include <gl/glu.h>#include <gl/glut.h>#include <gl/glaux.h>2，打开ClassWizard,选择CCY457OpenGLView类，为下述消息加入消息处理函数：WM_CREATE (for OnCreate), WM_DESTROY (for OnDestroy), WM_SIZE (for OnSize),WM_ERASEBACKGROUND (for OnEraseBkground).3,在窗口创建之前我们必须设置窗口风格包含WS_CLIPCHILDREN和WS_CLIPSIBLINGS，从而避免OpenGL绘制到其他窗口中去。

如何在MFC中调用OpenGL第一步：在CView类cpp中添加头文件支持：#include <gl/GL.h>#include <gl/glut.h>第二步：更改窗口样式使其支持OpenGL.在CView类成员函数PreCreateWindow中添加代码cs.style|=WS_CLIPSIBLINGS|WS_CLIPCHILDREN;第三步：重写CView中的Create函数，在函数中添加代码CString ClassName=AfxRegisterWndClass(CS_OWNDC);第四步：重新设置像素格式，并将其设置为当前像素格式在CView类中添加public型成员函数BOOL SetupPixelFormat(HDC hDC);函数体如下：//step 3 重新设置像素格式BOOL CXXXMFCGLView::SetupPixelFormat(HDC hDC){//重新设置画图窗口的像素格式static PIXELFORMATDESCRIPTOR pfd ={sizeof(PIXELFORMATDESCRIPTOR), // size of this pfd1, // version numberPFD_DRAW_TO_WINDOW | // support windowPFD_SUPPORT_OPENGL | // support OpenGLPFD_DOUBLEBUFFER, // double bufferedPFD_TYPE_RGBA, // RGBA type24, // 24-bit color depth0, 0, 0, 0, 0, 0, // color bits ignored0, // no alpha buffer0, // shift bit ignored0, // no accumulation buffer0, 0, 0, 0, // accum bits ignored32, // 32-bit z-buffer0, // no stencil buffer0, // no auxiliary bufferPFD_MAIN_PLANE, // main layer0, // reserved0, 0, 0 // layer masks ignored };int pixelformat;//分配一个像素格式号if ( (pixelformat = ChoosePixelFormat(hdc, &pfd)) == 0 ){MessageBox(L"ChoosePixelFormat failed");return FALSE;}//设置为当前的像素格式if (SetPixelFormat(hdc, pixelformat, &pfd) == FALSE){MessageBox(L"SetPixelFormat failed");return FALSE;}return TRUE;}第五步：在CView类中添加消息WM_CREATE,在OnCreate函数中添加代码HDC hDC;HGLRC hRC;hDC=::GetDC(GetSafeHwnd());SetupPixelFormat(hDC);hRC=wglCreateContext(hDC);wglMakeCurrent(hDC, hRC);第六步：初始化OpenGL重写CView类中的OnInitialUpdate，根据需要在OnInitialUpdate中添加代码这里OnInitialUpdate的作用与常用的OpenGL控制台程序中init()相同例如://初始化OpenGL//////////////////////////////////////////////////////glClearColor(1.0, 1.0, 1.0, 1.0);glEnable(GL_SMOOTH);glEnable(GL_DEPTH_TEST);//set material property1glNewList(0, GL_COMPILE);glEnable(GL_COLOR_MATERIAL);GLfloat mat_ambient[]={0.15, 0.07, 0.04, 1.0}; //原材料的环境颜色GLfloat mat_diffuse[]={0.15, 0.07, 0.04, 1.0}; //原材料的散射颜色GLfloat mat_specular[]={0.15, 0.07, 0.04, 1.0}; //原材料的反射颜色GLfloat mat_emission[]={0.15, 0.07, 0.04, 1.0}; //原材料的发散颜色glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);glMaterialf(GL_FRONT, GL_SHININESS, 50.0);glMaterialfv(GL_FRONT, GL_EMISSION, mat_emission);glEndList();//set light0glNewList(1, GL_COMPILE);glEnable(GL_LIGHTING);GLfloat light0_position[]={1.0, 1.0, 1.0, 1.0};GLfloat light0_spot_direction[]={-1.0, -1.0, -1.0, 1.0};GLfloat light0_ambient[]={0.015, 0.007, 0.004, 1.0};GLfloat ligh0_diffuse[]={1.0, 1.0, 1.0, 1.0};GLfloat light0_specular[]={1.0, 1.0, 1.0, 1.0};glLightfv(GL_LIGHT0, GL_POSITION, light0_position);glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, 45);glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, light0_spot_direction);glLightfv(GL_LIGHT0, GL_AMBIENT, light0_ambient);glLightfv(GL_LIGHT0, GL_DIFFUSE, ligh0_diffuse);glLightfv(GL_LIGHT0, GL_SPECULAR, light0_specular);glEnable(GL_LIGHT0);glEndList();//////////////////////////////////////////////////////第七步：在CView类中添加WM_SIZE的消息响应函数OnSize这里OnSize的作用与OpenGL控制台编程中reshape的作用相同根据需要在其中添加代码例如：//////////////////////////////////////////////////////glCallList(1);glViewport(0, 0, cx, cy);glMatrixMode(GL_PROJECTION);glLoadIdentity();if (cx <= cy)gluOrtho2D (-1.0, 1.0,-1.0*(GLfloat)cy/(GLfloat)cx, 1.0*(GLfloat)cy/(GLfloat)cx);elsegluOrtho2D (-1.0*(GLfloat)cx/(GLfloat)cy,1.0*(GLfloat)cx/(GLfloat)cy, -1.0, 1.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();//////////////////////////////////////////////////////第八步：根据需要在CView类OnDraw函数中添加代码绘图在这里OnDraw的功能与OpenGL按制台编程中的display函数相同例如：//////////////////////////////////////////////////////glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);glRotatef(0, 1.0f, 0.0f, 0.0f);glRotatef(0, 0.0f, 1.0f, 0.0f);glCallList(0);glutSolidTeapot(0.5);glPushMatrix();glTranslatef(-0.8, -0.3, -0.2);glutSolidTorus(0.1, 0.2, 50, 60);glPopMatrix();glPushMatrix();glTranslatef(0.9, 0, 0);glutSolidSphere(0.2, 80, 80);glPopMatrix();glFlush();SwapBuffers(wglGetCurrentDC());//////////////////////////////////////////////////////第九步：在CView类中添加WM_DESTROYR的消息响应函数OnDestroy 在其中添加如下代码：HGLRC hRC;hRC=wglGetCurrentContext();wglMakeCurrent(NULL, NULL);if (hRC){wglDeleteContext(hRC);}到这里，一个完整的MFC调用OpenGL的程序就大功告成了。

MFC下OpenGL入门源文件1，建一工程文件，我这里命名为first，现在first工程里面我们没有添加任何东西，所有的东西都是MFC自动帮我们创建的。

2，添加链接库。

这一步很关键。

打开菜单栏下的项目->属性->配置属性->链接器->输入->附加依赖项里加入OpenGL32.lib GLu32.lib GLaux.lib，如图3，加头文件，在stdafx里面添加opengl的头文件。

如下代码所示：//-----------------------Tramp---添加OpenGL库头文件----------------------------->#include "stdio.h"#include "math.h"#include "gl\gl.h"#include "gl\glu.h"#include "gl\glaux.h"//---------------------------------------------------------------------------<代码4， CCY457OpenGLView类的属性栏，为下述消息加入消息处理函数：WM_CREATE (for OnCreate), WM_DESTROY (for OnDestroy), WM_SIZE (forOnSize), WM_ERASEBACKGROUND (for OnEraseBkground).如下图：5，设置窗口显示风格。

窗口创建之前我们必须设置窗口风格包含WS_CLIPCHILDREN 和WS_CLIPSIBLINGS，从而避免OpenGL绘制到其他窗口中去。

这些应该放在PreCreateWindow()中。

B OOL CfirstView::PreCreateWindow(CREATESTRUCT& cs){// TODO: 在此处通过修改// CREATESTRUCT cs 来修改窗口类或样式cs.style |= WS_CLIPSIBLINGS | WS_CLIPCHILDREN;//Trampreturn CView::PreCreateWindow(cs);}代码6，在CfirstView.h中加入如下语句：/************************************************************************//* 设置的变量是Rendering Context(着色描述表)。

基于MFC的OpenGL绘图本文更新版本请点击[置顶]《基于MFC的OpenGL编程》系列文章一、简介GDI是通过设备句柄（Device Context以下简称"DC"）来绘图，而OpenGL则需要绘制环境（Rendering Context，以下简称"RC"）。

每一个GDI命令需要传给它一个DC，但与GDI不同，OpenGL使用当前绘制环境(RC)。

一旦在一个线程中指定了一个当前RC，在此线程中其后所有的OpenGL命令都使用相同的当前RC。

虽然在单一窗口中可以使用多个RC，但在单一线程中只有一个当前RC。

下面我将首先产生一个OpenGL RC并使之成为当前RC，这将分为三个步骤：设置窗口像素格式；产生RC；设置为当前RC。

二、MFC中的OpenGL基本框架1、首先创建工程用AppWizard产生一个MFC EXE项目，其他默认即可。

2、将此工程所需的OpenGL文件和库加入到工程中在工程菜单中，选择"Build"下的"Settings"项。

单击"Link"标签，选择"General"目录，在Object/Library Modules的编辑框中输入"opengl32.lib glu32.lib glut.lib glaux.lib"（注意，输入双引号中的内容，各个库用空格分开；否则会出现链接错误），选择"OK"结束。

然后打开文件"stdafx.h"，加入下列头文件：#include <gl\gl.h>#include <gl\glu.h>3、改写OnPreCreate函数并给视图类添加成员函数和成员变量OpenGL需要窗口加上WS_CLIPCHILDREN（创建父窗口使用的Windows风格，用于重绘时裁剪子窗口所覆盖的区域）和WS_CLIPSIBLINGS（创建子窗口使用的Windows风格，用于重绘时剪裁其他子窗口所覆盖的区域）风格。