高达二阶的球谐函数（3 个波段，9 个系数）。
球谐函数 (SH) 表示各方向上的函数或信号，常在计算机图形中用于高效计算平滑光照。Unity 将它们用于 LightProbes 和环境光照。
L2 球谐函数由 9 个系数（用于每个颜色通道）组成。
另请参阅：RenderSettings.ambientMode、RenderSettings.ambientProbe、LightProbes。
| this[int,int] | 访问各个 SH 系数。 |
| AddAmbientLight | Add an ambient light to the spherical harmonics. |
| AddDirectionalLight | Add a directional light to the spherical harmonics. |
| Clear | Clears the spherical harmonics coefficients to zero. |
| Evaluate | Evaluates the spherical harmonics for each given direction. The directions and results arrays must have the same size. |
| operator != | Returns true if the spherical harmonics are different. |
| operator * | 按给定系数缩放 SH。 |
| operator + | Adds two spherical harmonics. |
| operator == | Returns true if the spherical harmonics are equal. |