OpenGL Draw Around a Circle At Angles

Question

I am trying to draw an image at 45 degree increments in the shape of a circle. I am getting the image from a txt file. I am trying to translate the matrix by 45 degrees but its not working.

This is what I tried but it's not working:

glBegin(GL_LINE_STRIP);
glColor3f(0, 0,0);
for(int ii=0; ii<8; ii++){
    float theta = 2*PI * float(ii)/8;
    glVertex2f(cx+r*cos(theta), cy+r*sin(theta));
}
glEnd();

You can't change the matrix in between glBegin and glEnd. But I don't get why you have this outside glBegin/glEnd at all. Put glBegin/glEnd around each individual image. — user253751, Jan 27 '23 at 17:16
it looks like you are trying to do the right things but in the wrong order — user253751, Jan 27 '23 at 17:17

score 0 · Accepted Answer · answered Jan 27 '23 at 17:35

You want to draw the shape 8 times in different places, right?

So the program would look like this: (I will not show the exact code but enough to make you understand it)

for(int ii=0; ii<8; ii++) {
    push the matrix;
    calculate the position/rotation based on ii and change the matrix;
    draw the shape;
    pop the matrix;
}

And how do you draw the shape? Well, I guess you already know how to draw the shape and you draw the shape like this: (I think you already wrote this code, so I can show it)

glBegin(GL_LINE_STRIP);
for (auto i : floatPairs) {
    glVertex2f(i.first, i.second);
}
glEnd();

OpenGL Draw Around a Circle At Angles

1 Answers1