1*bf2c3715SXin Li 2*bf2c3715SXin LiNavigation: 3*bf2c3715SXin Li left button: rotate around the target 4*bf2c3715SXin Li middle button: zoom 5*bf2c3715SXin Li left button + ctrl quake rotate (rotate around camera position) 6*bf2c3715SXin Li middle button + ctrl walk (progress along camera's z direction) 7*bf2c3715SXin Li left button: pan (translate in the XY camera's plane) 8*bf2c3715SXin Li 9*bf2c3715SXin LiR : move the camera to initial position 10*bf2c3715SXin LiA : start/stop animation 11*bf2c3715SXin LiC : clear the animation 12*bf2c3715SXin LiG : add a key frame 13*bf2c3715SXin Li 14