Jump to content
  • Advertisement
Sign in to follow this  
leahayes00

Generating a Circle Mesh

This topic is 5146 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hi, I have a basic data structure like this: struct POINT { float x, y; }; and an array like this: vector<POINT> CirclePoints; How can I generate a circle, i.e. calculate the vertex positions, when the circle has n vertices or s sides? When the circle has three sides it should be like this: (Ignore the _ symbols) ___. __._. Four sides: ___. __._. ___. Five sides: ____. __.___. ___. . Six sides: _____. . ___._____. _____. . etc... Any help would be greatly appreciated! Best Regards, Lea Hayes

Share this post


Link to post
Share on other sites
Advertisement
Quote:
Original post by mike25025
for num of sides n do add point (x = sin(360/n),y = cos(360/n))

hope that helps


for (i = 0; i < n; i++)
{
xi = sin(i*360/n),yi = cos(i*360/n)
}

Share this post


Link to post
Share on other sites
Actually, do this instead. I'm assuming vector is std::vector.


N = number of points
TWOPI = 6.28319;

// reserve memory to avoid lots of memory reallocs
CirclePoints.reserve(N);

// make sure vector is empty. Do NOT do a clear()!
CirclePoints.resize(0);

POINT center; // centerpoint
POINT newpoint;
for (i = 0; i < N; i++)
{
newpoint.x = center.x + radius * cosf(i * TWOPI / N);
newpoint.y = center.y + radius * sinf(i * TWOPI / N);
CirclePoints.push_back(POINT
}


Two things. First, I'm using TWOPI instead of 360 since most compilers require an angle in radians when you call cos/sin. 360 is degrees, TWOPI is radians.

Second, that loop will generate a circle that is not closed. If you want enough points to close the circle (e.g., if you draw a line between points 0 and 1, 1 and 2, ..., N-1 and N, you end up with a closed circle, then change the N in the denominator of the newpoint.x/y equations to be (N-1) instead.

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
×

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

We are the game development community.

Whether you are an indie, hobbyist, AAA developer, or just trying to learn, GameDev.net is the place for you to learn, share, and connect with the games industry. Learn more About Us or sign up!

Sign me up!