动画常量（Animation Constants）
循环模式
THREE.LoopOnce THREE.LoopRepeat THREE.LoopPingPong
插值模式
THREE.InterpolateDiscrete THREE.InterpolateLinear THREE.InterpolateSmooth
结束模式
THREE.ZeroCurvatureEnding THREE.ZeroSlopeEnding THREE.WrapAroundEnding
源代码
推荐：用 NSDT场景编辑器 快速搭建3D场景。
THREE.LoopOnce THREE.LoopRepeat THREE.LoopPingPong
THREE.InterpolateDiscrete THREE.InterpolateLinear THREE.InterpolateSmooth
THREE.ZeroCurvatureEnding THREE.ZeroSlopeEnding THREE.WrapAroundEnding