openGL画直线、圆、椭圆

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);

glV ertex3f(xc+x,yc+y,0);

glV ertex3f(xc-x,yc+y,0);

glV ertex3f(xc+x,yc-y,0);

glV ertex3f(xc-x,yc-y,0);

glV ertex3f(xc+y,yc+x,0);

glV ertex3f(xc-y,yc+x,0);

glV ertex3f(xc+y,yc-x,0);

glV ertex3f(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(x

{

plot_circle_points(xc,yc,x,y);

if(p<0)

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);

glV ertex3f(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)

{

if(d1<0)

{

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)*(y-1)-a*a*b*b;

while(y>0)

{

if(d2<=0)

{

d2+=b*b*(2*x+2)+a*a*(-2*y+3);

x++;

y--;

}

else

{

d2+=a*a*(-2*y+3);

y--;

}

putpixel(xc,yc,x,y);

putpixel(xc,yc,-x,-y);

putpixel(xc,yc,-x,y);

putpixel(xc,yc,x,-y);

}

}

void dda_line(int xa,int ya,int xb,int yb)//画直线

{

GLfloat delta_x,delta_y,x,y;

int dx,dy,steps;

dx=xb-xa;

dy=yb-ya;

if(abs(dx)>abs(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);

glV ertex3f(x,y,0);

for(int k=1;k<=steps;k++)

{

x+=delta_x;

y+=delta_y;

glBegin(GL_POINTS);

glV ertex3f(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 glV iewport 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 glV iewport 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 glV iewport 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<<"************************************************"<

cout<<"**** 请选择如下操作: *****"<

cout<<"**** 1.用DDA画线*****"<

cout<<"**** 2.用Bresenham算法画圆*****"<

cout<<"**** 3.用Bresenham算法画椭圆*****"<

cout<<"************************************************"<

cout<<"请选择如下操作:";

int choice;

cin>>choice;

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"); /* window title */

glutDisplayFunc(display3); /* display callback invoked when window opened */ myinit(); /* set attributes */

glutMainLoop(); /* enter event loop */

default: return 0;

}

return 0;

}