OPENGL+GLUT 实现一个简单的3d场景漫游。方向键控制前进后退和旋转，F1键控制视角切换（人物漫游视角和物体控制视角）-OPENGL+GLUT implement a simple 3d scene roaming. Arrow keys to control the forward and backward rotation, F1 keys to control angle switching (roaming characters and objects in the Perspe