OpenGLは中点法で直線と円を描きます。
本論文の実例はOpenGLの直線と円を描く具体的なコードを共有しています。参考にしてください。具体的な内容は以下の通りです。
#include <gl/glut.h>
#include <math.h>
static int i=1;
void Initial(void)
{
glClearColor(1.0f, 1.0f, 1.0f, 1.0f); //
glMatrixMode(GL_PROJECTION); //
gluOrtho2D(-200.0,200.0,-200.0,200.0); // // ， (0,200,0,200) ， 1/4 ， 1，3 ， 2，4
}
/*void Display(void)
{
glClear(GL_COLOR_BUFFER_BIT); //
glColor3f(1.0f, 0.0f, 0.0f); //
glRectf(50.0f, 100.0f, 150.0f, 50.0f); //
glFlush(); // OpenGL
}
*/
void DDALine(int x0,int y0,int x1,int y1)
{
//glVertex2f(10,10);
int dx,dy,epsl,k;
float x,y,xIncre,yIncre;
dx = x1 - x0;
dy = y1 - y0;
x = x0;
y = y0;
if(abs(dx)>abs(dy))
epsl=abs(dx);
else
epsl=abs(dy);
xIncre=(float)dx/(float)epsl;
yIncre=(float)dy/(float)epsl;
glPointSize(2);
glBegin(GL_POINTS);
for(k = 0;k <= epsl; k++)
{
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(int(x+0.5),int(y+0.5));
x += xIncre;
y += yIncre;
}
glEnd();
}
void Mid_B(int x0,int y0,int x1,int y1)
{
int dx,dy,d,UpIncre,DownIncre,x,y;
if(x0 > x1)
{
x = x1;
x1 = x0;
x0 = x;
y = y1;
y1 = y0;
y0 = y;
}
x = x0;
y = y0;
dx = x1 - x0;
dy = y1 - y0;
d = dx - 2*dy;
UpIncre = 2*dx - 2*dy;
DownIncre =- 2*dy;
glPointSize(2);
glBegin(GL_POINTS);
while(x <= x1)
{
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(x,y);
x++;
if(d < 0)
{
y++;
d += UpIncre;
}
else
d += DownIncre;
}
glEnd();
}
void G_B(int x0,int y0,int x1,int y1)
{
int x,y,dx,dy,e;
dx = x1 - x0;
dy = y1 - y0;
e =- dx;
x=x0;
y=y0;
glPointSize(2);
glBegin(GL_POINTS);
while(x <= x1)
{
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(x,y);
x++;
e = e + 2*dy;
if(e > 0)
{
y++;
e = e - 2*dx;
}
}
glEnd();
}
void CirclePoint(int x, int y)
{
glPointSize(2);
glBegin(GL_POINTS);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(x,y);
glVertex2f(y,x);
glVertex2f(-y,x);
glVertex2f(-x,y);
glVertex2f(-x,-y);
glVertex2f(-y,-x);
glVertex2f(y,-x);
glVertex2f(x,-y);
glEnd();
}
void MidBresenhamCircle(int r)
{
int x = 0, y = r, d = 1-r;
//glPointSize(2);
//glBegin(GL_POINTS);
while(x <= y)
{
CirclePoint(x,y);
if(d < 0)
d += 2*x+3;
else
{
d += 2*(x-y)+5;
y--;
}
x++;
}
glEnd();
}
void ProcessMenu(int value)
{
i = value;
glutPostRedisplay();
}
void Display(void)
{
glClear(GL_COLOR_BUFFER_BIT); //
glViewport(0,0,400,400); // ， （ ）
switch(i)
{
case 1:
DDALine(2,3,55,83);
break;
case 2:
Mid_B(2,3,55,83);
break;
case 3:
G_B(2,3,55,83);
break;
case 4:
MidBresenhamCircle(50);
break;
}
glFlush();
}
int main(int argc, char* argv[])
{
glutInit(&argc, argv); // GLUT ,
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); //
glutInitWindowSize(400,400); //
glutInitWindowPosition(100,100); //
glutCreateWindow(" "); //
int MainMenu = glutCreateMenu(ProcessMenu); //
glutAddMenuEntry("DDA ",1);
glutAddMenuEntry(" Bresenham ",2);
glutAddMenuEntry(" Bresenham ",3);
glutAddMenuEntry(" bresenham ",4);
glutAttachMenu(GLUT_RIGHT_BUTTON);
glutDisplayFunc(Display); //
Initial(); //
glutMainLoop(); // GLUT
return 0;
}