openGL画直线、圆、椭圆.doc

使用openGl画直线（DDA算法）、画圆、椭圆（Bresenham算法） #includestdlib.h #includeiostream.h #include GL/glut.h /* 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) { d1+=b*b*(2*x+3); x++; } else { d1+=b*b*(2*x+3)+a*a*(-2*y+2); x++; y--; } putpixel(xc,yc,x,y); putpixel(xc,yc,-x,-y); putpixel(xc,yc,-x,y); putpixel(xc,yc,x,-y); } d2=b*b*(x+0.5)*(x+0.5)+a*a*(y-1)*(