openGL画直线、圆、椭圆.doc

使用openGl画直线（DDA算法）、画圆、椭圆（Bresenham算法）#include#include #include /* initialization: */ void myinit(void) /* attributes */ glClearColor(1.0, 1.0, 1.0, 0.0); /* white background */ glColor3f(1.0, 0.0, 0.0); /* draw in red */ /* set up viewing: */ /* 500 x 500 window with origin lower left */ glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D(0.0, 500.0, 0.0, 500.0); glMatrixMode(GL_MODELVIEW); void plot_circle_points(int xc,int yc,int x,int y)/画圆 glBegin(GL_POINTS); glVertex3f(xc+x,yc+y,0); glVertex3f(xc-x,yc+y,0); glVertex3f(xc+x,yc-y,0); glVertex3f(xc-x,yc-y,0); glVertex3f(xc+y,yc+x,0); glVertex3f(xc-y,yc+x,0); glVertex3f(xc+y,yc-x,0); glVertex3f(xc-y,yc-x,0); glEnd();void drawcircle(int xc,int yc,int radius) int x,y,p; x=0; y=radius; p=3-2*radius; glClear(GL_COLOR_BUFFER_BIT); glBegin(GL_POINTS); while(xy) plot_circle_points(xc,yc,x,y); if(p0) p=p+4*x+6; else p=p+4*(x-y)+10; y-=1; x+=1; if(x=y) plot_circle_points(xc,yc,x,y); void putpixel(int xc,int yc,int x,int y)/画椭圆glBegin(GL_POINTS); glVertex3f(xc+x,yc+y,0); glEnd();void drawEllipse(int xc,int yc,int a,int b) int x,y;float d1,d2;x=0;y=b;d1=b*b+a*a*(-b+0.25);putpixel(xc,yc,x,y);putpixel(xc,yc,-x,-y);putpixel(xc,yc,-x,y);putpixel(xc,yc,x,-y);while(b*b*(x+1)a*a*(y-0.5)if(d10)if(d2abs(dy) steps=abs(dx); else steps=abs(dy); delta_x=(GLfloat)dx/(GLfloat)steps; delta_y=(GLfloat)dy/(GLfloat)steps; x=xa; y=ya; glClear(GL_COLOR_BUFFER_BIT); glBegin(GL_POINTS); glVertex3f(x,y,0); for(int k=1;k=steps;k+) x+=delta_x; y+=delta_y; glBegin(GL_POINTS); glVertex3f(x,y,0); glEnd(); /* the display callback: */ void display1() /画圆 glClear(GL_COLOR_BUFFER_BIT); /*clear the window */ /*-*/ /* viewport stuff */ /*-*/ /* set up a viewport in the screen window */ /* args to glViewport are left, bottom, width, height */ glViewport(0, 0, 500, 500); /* NB: default viewport has same coords as in myinit, */ /* so this could be omitted: */dda_line(20,20,420,350); /* and flush that buffer to the screen */ glFlush(); void display2() /画圆 glClear(GL_COLOR_BUFFER_BIT); /*clear the window */ /*-*/ /* viewport stuff */ /*-*/ /* set up a viewport in the screen window */ /* args to glViewport are left, bottom, width, height */ glViewport(0, 0, 500, 500); /* NB: default viewport has same coords as in myinit, */ /* so this could be omitted: */drawcircle(250,250,100); /* and flush that buffer to the screen */ glFlush(); void display3() /画圆 glClear(GL_COLOR_BUFFER_BIT); /*clear the window */ /*-*/ /* viewport stuff */ /*-*/ /* set up a viewport in the screen window */ /* args to glViewport are left, bottom, width, height */ glViewport(0, 0, 500, 500); /* NB: default viewport has same coords as in myinit, */ /* so this could be omitted: */drawEllipse(250,250,60,40); /* and flush that buffer to the screen */ glFlush(); int main(int argc, char* argv) /* Standard GLUT initialization */ glutInit(&argc,argv); glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); /* default, not needed */ glutInitWindowSize(500,500); /* 500 x 500 pixel window */ glutInitWindowPosition(0,0); /* place window top left on display */cout*endl;cout* 请选择如下操作: *endl;cout* 1.用DDA画线 *endl;cout* 2.用Bresenham算法画圆 *endl;cout* 3.用Bresenham算法画椭圆 *endl;cout*endl;coutchoice;switch(choice)case 1: glutCreateWindow(Bresenham circile); /* window title */ glutDisplayFunc(display1); /* display callback invoked when window opened */ myinit(); /* set attributes */ glutMainLoop(); /* enter event loop */break;case 2: glutCreateWindow(Digital Differential Analyser Line); /* window title */ glutDisplayFunc(display2); /* display callback invoked when window opened */ myinit(); /* set attributes */ glutMainLoop(); /* enter event loop */break;case 3:glutCreateWindow(MidBresenhamEllipse