Original Post
I read the billboarding tutorial on Lighthouse 3D. http://www.lighthouse3d.com/opengl/billboarding/index.php3?billCheat2 According to the tutorial, he use up and right vector to define the vertices of the quad. a = center - right * (size * 0.5); b = center + right * size * 0.5; c = center + right * size * 0.5 + up * size; d = center - right * size * 0.5 + up * size; What's the meaning of the above expressions? Thank you!