3D Sphere OpenGL?

Question

I would like to create a Sphere, actually a globe. But i can't seem to find any helpful information about how to handle the vertices and indices to a sphere, how to set them up. Could any of you lead me on to the right track, maybe give me some example code or link to a tutorial?

Answer 1

There are a few techniques that work for generating spheres.

Primary ones are:

Polar Coordinates: Translating polar or spherical coordinates into cartesian ones

Normalized Cube: starting with a subdivided unit cube (extents (-1,-1,-1) to (1,1,1)) and normalizing the verticies.

This article contains some psuedocode that may help you:

https://medium.com/game-dev-daily/four-ways-to-create-a-mesh-for-a-sphere-d7956b825db4

There is a more detailed explanation on of using a normalized cube method his website, which also covers calculating a continuous tangent space.

https://www.iquilezles.org/www/articles/patchedsphere/patchedsphere.htm

Hopefully these links will help you generate the sphere verticies, the indicies might be a bit of trouble.

The normalized cube technique is probably the easiest way, since it is fairly easy to generate a subdivided cube mesh with proper indicies one quad at a time.

Generating a sphere using polar coordinates is a bit more difficult, and the result is arguably a bit worse.

Note: if you do decide to use the Polar Coordinates method, what the medium author calls "UV Sphere"/"Standard Sphere" is using polar coordinates, which are angles.

spherical_to_cartesian in that example is likely something doing something like the following (which the medium author does not have in his own article)

x = cos(meridian)

z = sin(meridian)

y = sin(parallel)

f = cos(parallel)

return (x*f, y, z*f)

Also Psuedocode, for simplicity.