Skybox vs Skysphere

Question

What are some advantages and disadvantages between the two. Especially for something like a 3D game.

Answer 1

Skyboxes and skyspheres are pretty much equivalent in the sense that you will get the same kind of visual effect - i.e. a nice background that appears to be at a long distance away.

However I'd normally recommend a skybox for the following three reasons:

• Less polygons required
• Assuming you set up your projection matrices correctly, you can't tell that you are inside a box (if you get it wrong, you may see some distortions)
• It's easier to render square skybox images (one for each of the size directions)

Regarding the last point, it is pretty easy to configure a renderer to produce raytraced square images that exactly fit on a skybox by creating a 90 degree field of view, e.g. in POVRay you would use something like the following:

camera {
   right -x
   up y
   direction -z
   location 0
}

I typically use 1024*1024 or 2048*2048 square textures for this.

The one good reason I can think of to use a skysphere is if you are using some kind of procedural texture approach that requires generation at (approximately) the points on a unit sphere. I think that is a pretty special case however, and unlikely to be necessary for most gaming applications.