基于webgl实现stl格式3d文件读取与显示，自动调整其大小使其适应显示窗口大小，并自动实现其居中显示，以及实现鼠标操作放大缩小平移-3d stl format based webgl achieve read and display file, automatically adjusts its size to adapt to the size of the display window and automatically achieve its centered, and the rea