We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.
Hardware

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

What Is an OpenGL® Sphere?

By Eugene P.
Updated: May 16, 2024
Views: 7,458
Share

An Open Graphics Library® (OpenGL®) sphere, at the most basic level, is a three-dimensional (3D) object made up of a series of triangles or quadrilaterals whose vertices are all equidistant from a center point. This means that, when an OpenGL® sphere is viewed from any angle, the outline appears as a perfect circle to the viewer, although lighting and shading might give the volume a more ball-like appearance. The number of vertices used to create an OpenGL® sphere determines the smoothness of the object in its approximation of an actual sphere, with any less than 12 points creating an object that cannot be considered a sphere. Even though a sphere is considered a shape primitive in many graphical applications and libraries, OpenGL® does not have any innate functionality to render a sphere, meaning supplementary toolkits such as the OpenGL® utility toolkit (GLUT) need to be used to avoid writing code to manually generate the shape.

When dealing with vertices in OpenGL®, the least amount of points that can be used to generate a sphere with some degree of smoothness is 12, creating an object with 20 triangular faces known as an icosahedron. Without further processing, an OpenGL® sphere constructed in this way will have visible sharp corners around the edges, which might be acceptable for some applications. To achieve a more rounded sphere, each face needs to be further subdivided.

Subdividing an icosahedron to increase the number of vertices it contains and form a smoother OpenGL® sphere involves creating new vertices in the center of each edge of each existing triangle. This means each triangular face will now contain four triangles. The subdivision can continue as much as required, although adding points exponentially can quickly create an object that has a high render time and can become unwieldy to translate.

Despite some of the mathematical conveniences an OpenGL® sphere provides for programmers, such as the surface normals that can be readily calculated from the vertex coordinates, texturing a sphere can present some complexities. Using a standard two-dimensional (2D) texture projected onto the sphere means that the top and bottom areas of the texture image will become compressed, because the shape of the triangles near the poles of the sphere are compressed themselves. To overcome this, cube mapping could be used or the programmer could generate the texture coordinates manually for the object.

One factor should be noted about using a utility library for generating an OpenGL® sphere. A sphere generated by GLUT or similar toolkits can sometimes be difficult to modify, optimize and manage within OpenGL® itself. For this reason, it is sometimes beneficial to use custom written code to generate an OpenGL® sphere so it is created and can be used in the most efficient way possible within the program.

Share
EasyTechJunkie is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
Share
https://www.easytechjunkie.com/what-is-an-opengl-sphere.htm
Copy this link
EasyTechJunkie, in your inbox

Our latest articles, guides, and more, delivered daily.

EasyTechJunkie, in your inbox

Our latest articles, guides, and more, delivered daily.