For a practical course at university, I had to write an OpenGL game from scratch, without using a game engine. One of the first tasks was to load glTF files with 3d models. Actually, this image should display a yellow rubber duck. Instead, it turned out to be a colorful gem. I am not completely sure what went wrong but my guess is that I accidentally interpreted the normal buffer as the position buffer. With increasing complexity of the loaded model, the displayed object looked more and more like a sphere.