获取和设置用于为每个 LOD 启用法线贴图的布尔值数组。
Because normal mapping comes with an increased performance cost, you may want to only render normal maps on the SpeedTree assets that are nearest to the player. You can use this feature to improve performance by disabling normal mapping on some of your less detailed LOD levels where the models are far enough away from the camera that the absence of this effect is not noticeable. The array length that you supply must match the number of LOD levels in your SpeedTree asset, and typically would have true values at the start, and false values at the end. For example, if your SpeedTree asset has three LOD levels, you might pass an array of [ true, true, false ] to enable normal mapping on the first two LOD levels, but disable it on the third.