OpenGL Draw Pentagram

Set Pentagram 5 vertices are abcde, vertex to axis origin distance is R,ABCDE each point with R, respectively,

A (0,R);

B (-r*sin (2/5*PI), R*cos (2/5*PI));

C (-r*sin (PI/5),-r*cos (PI/5));

De and CB about y axisymmetric.

After determining the coordinates of the 5 vertices, the Gl_line_loop function is used to connect 5 points, sequentially acebd.

The main code is:

 
 
 1 void Star(void)
 2 {
 3 
 4     GLfloat r = 0.8f;
 5     GLfloat PointA[2] = { 0, r };
 6     GLfloat PointB[2] = { -r*sin(0.4*Pi), r*cos(0.4*Pi) };
 7     GLfloat PointC[2] = { -r*sin(Pi / 5), -r*cos(Pi / 5) };
 8     GLfloat PointD[2] = { r*sin(Pi / 5), -r*cos(Pi / 5) };
 9     GLfloat PointE[2] = { r*sin(0.4*Pi), r*cos(0.4*Pi) };
10 
11     glClear(GL_COLOR_BUFFER_BIT);
12 
13     glBegin(GL_LINE_LOOP);
14     glVertex2fv(PointA);
15     glVertex2fv(PointC);
16     glVertex2fv(PointE);
17     glVertex2fv(PointB);
18     glVertex2fv(PointD);
19 
20     glEnd();
21 
22     glFinish();
23 }

The results of the drawing are as follows:

OpenGL Draw Pentagram