OpenGL 基础图形绘制与投影变换

本文参考《Computer Graphics Using OpenGL》,第一个例子绘制了

1. 参数定义的House

2. a flurry of filled rectangles

3. Sierpinski曲线

含有鼠标和键盘响应函数onmouse和onkeyboard。

/************************************************************************//* CreateTime:2013-2-18**Author:@Rachel Zhang**Discription: Draw Parameter House, Flurry and Sierpinski**3rd-party:OpenGL*//************************************************************************/#include "GL/glut.h"#include "stdlib.h"#include <iostream>using namespace std;#define screenHeight 480class GLintPoint{public: GLint x, y;};// Create a number between 0 and m(a number which will be given)// the input m must be less than 32767 according to P49 in <Computer Graphics Using OpenGL>int random(int m){return rand()%m;}void drawDot (GLint x, GLint y){glPointSize(3);glBegin(GL_POINTS);glVertex2i(x,y);glEnd();}typedef struct{GLfloat r, g, b;} GLfloatRGBColour;GLfloatRGBColour colour[8] = { {0.0f, 0.0f, 0.0f}, {0.0f, 0.0f, 1.0f},{0.0f, 1.0f, 0.0f}, {1.0f, 0.0f, 0.0f},{0.0f, 1.0f, 1.0f}, {1.0f, 0.0f, 1.0f},{1.0f, 1.0f, 0.0f}, {1.0f, 1.0f, 1.0f}};void setPenColour(GLfloatRGBColour newColour){glColor3f(newColour.r, newColour.g, newColour.b);}/************************************************************************//*                                Draw Functions                                      *//************************************************************************/void parameterizedHouse(GLintPoint peak, GLint width, GLint height)// the top of house is at the peak; the size of house is given//  by height and width{glBegin(GL_LINE_LOOP);glVertex2i(peak.x,             peak.y);  // draw shell of house glVertex2i(peak.x + width / 2, peak.y - 3 * height /8);glVertex2i(peak.x + width / 2,  peak.y -     height);glVertex2i(peak.x - width / 2, peak.y -     height);glVertex2i(peak.x - width / 2, peak.y - 3 * height /8);glEnd();}void drawFlurry(int num, int Width, int Height)// draw num random rectangles in a Width by Height rectangle {for (int i = 0; i < num; i++) {GLint x1 = random(Width);// place corner randomly GLint y1 = random(Height);GLint x2 = random(Width); // pick the size so it fits GLint y2 = random(Height);GLfloat lev = random(10)/10.0;// random value, in range 0 to 1 glColor3f(lev,lev,lev);// set the gray level glRecti(x1, y1, x2, y2);// draw the rectangle}glFlush();}  void drawSierpinski(GLintPoint corner[3]){ int i, index, tcolour=0;GLintPoint point;point = corner[random(3)];drawDot(point.x, point.y);for (i = 0; i < 1000; i++){index = random(3);point.x = (point.x + corner[index].x)/2;point.y = (point.y + corner[index].y)/2;  tcolour = (++tcolour)%7;       // col = (col + 1) mod 7;setPenColour(colour[tcolour]);drawDot(point.x, point.y);}}/************************************************************************//*                         Mouse Listener and keyboard Listener                    *//************************************************************************/void myMouse(int button, int state, int x, int y){static GLintPoint corners[3];static int numCorners;if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN){corners[numCorners].x = x;corners[numCorners].y = screenHeight - y - 1;if (++numCorners == 3){drawSierpinski(corners);numCorners = 0;}}else if (button==GLUT_RIGHT_BUTTON)glClear(GL_COLOR_BUFFER_BIT);glFlush();}void onKeyBoard(unsigned char key,int mousex, int mousey){switch (key){case 'q':exit(0);case 'r':static GLintPoint corners[3];for (int i=0;i<3;i++){corners[i].x = random(640);corners[i].y = random(screenHeight);}drawSierpinski(corners);default:break;}}// Initialization void Init(void)     {glClearColor(1.0,1.0,1.0,0.0); // Set white background colorglColor3f(0.0f,0.0f,0.0f);    // Set the drawing colorglMatrixMode(GL_PROJECTION);glLoadIdentity();gluOrtho2D(0.0,640.0,0.0,480.0);}void myDisplay(){glClear(GL_COLOR_BUFFER_BIT);       //clear the screenGLintPoint Mypoint = {200,100};parameterizedHouse(Mypoint,100,100);drawFlurry(4,100,100);glFlush();}void main(int argc,char *argv[]){glutInit(&argc, argv);  // Initialize the toolkitglutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);  // Set display modeglutInitWindowPosition(100, 150);  // Set window pozition on screenglutInitWindowSize(640, 480);      // Set window sizeglutCreateWindow("parameterizedHouse, Flurry and drawSierpinski"); // Open the screen windowglutDisplayFunc(myDisplay); // Register redraw function glutMouseFunc(myMouse);glutKeyboardFunc(onKeyBoard);Init();glutMainLoop();  // Go into a perpetual loop}

效果图：

第二个例子绘制了这样一系列图形：

在其中有空间投影变换，主要应用了三个函数：

投影变换函数glViewport(), 矩阵平移函数glTranslated() 和正射投影函数 glOrtho()

上图实现代码参考《计算机图形学-用OpenGL实现第2版》：

#include <windows.h>  //suitable when using Windows 95/98/NT#include <gl/Gl.h>#include <gl/Glu.h>#include <gl/glut.h>//<<<<<<<<<<<<<<<<<<< axis >>>>>>>>>>>>>>void axis(double length){ // draw a z-axis, with cone at endglPushMatrix();glBegin(GL_LINES);glVertex3d(0, 0, 0); glVertex3d(0,0,length); // along the z-axisglEnd();glTranslated(0, 0,length -0.2); glutWireCone(0.04, 0.2, 12, 9);glPopMatrix();}//<<<<<<<<<<<<<<<<<<<<<<<<<<<<< displayWire >>>>>>>>>>>>>>>>>>>>>>void displayWire(void){glMatrixMode(GL_PROJECTION); // set the view volume shapeglLoadIdentity();glOrtho(-2.0*64/48.0, 2.0*64/48.0, -2.0, 2.0, 0.1, 100);//正射投影函数glMatrixMode(GL_MODELVIEW); // position and aim the cameraglLoadIdentity();gluLookAt(2.0, 2.0, 2.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);//define viewpoint transformation//Draw axisglClear(GL_COLOR_BUFFER_BIT); // clear the screenglColor3d(0,0,0); // draw black linesaxis(0.5); // z-axisglPushMatrix(); glRotated(90, 0,1.0, 0);axis(0.5);// y-axisglRotated(-90.0, 1, 0, 0);axis(0.5);// z-axisglPopMatrix();//Draw CubeglPushMatrix();glTranslated(0.5, 0.5, 0.5); // multiply by a translation matrix, define center (0.5, 0.5, 0.5)glutWireCube(1.0);glPopMatrix();//Draw SphereglPushMatrix();glTranslated(1.0,1.0,0);// sphere at (1,1,0)glutWireSphere(0.25, 10, 8);glPopMatrix();//Draw ConeglPushMatrix();glTranslated(1.0,0,1.0);// cone at (1,0,1)glutWireCone(0.2, 0.5, 10, 8);glPopMatrix();//Draw TeapotglPushMatrix();glTranslated(1,1,1);glutWireTeapot(0.2); // teapot at (1,1,1)glPopMatrix();//Draw TorusglPushMatrix();glTranslated(0, 1.0 ,0); // torus at (0,1,0)glRotated(90.0, 1,0,0);glutWireTorus(0.1, 0.3, 10,10);glPopMatrix();//十二面体glPushMatrix();glTranslated(1.0, 0 ,0); // dodecahedron at (1,0,0)glScaled(0.15, 0.15, 0.15);glutWireDodecahedron();glPopMatrix();glPushMatrix();glTranslated(0, 1.0 ,1.0); // small cube at (0,1,1)glutWireCube(0.25);glPopMatrix();glPushMatrix();glTranslated(0, 0 ,1.0); // cylinder at (0,0,1)GLUquadricObj * qobj;qobj = gluNewQuadric();gluQuadricDrawStyle(qobj,GLU_LINE);gluCylinder(qobj, 0.2, 0.2, 0.4, 8,8);glPopMatrix();glFlush();}//<<<<<<<<<<<<<<<<<<<<<< main >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>void main(int argc, char **argv){glutInit(&argc, argv);glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB );glutInitWindowSize(640,480);glutInitWindowPosition(100, 100);glutCreateWindow("Transformation testbed - wireframes");glutDisplayFunc(displayWire);glClearColor(1.0f, 1.0f, 1.0f,0.0f);  // background is whiteglViewport(0, 0, 640, 480);//投影变换函数glutMainLoop();}

Reference:

http://www.oocities.org/uniq_friq/c_files/openGL/1lab/dots.htm