void Awake() {
      if (_instance) {
        throw new System.Exception("Singleton Exception.");
      }
      _instance = this;
      id_fogHorColor = Shader.PropertyToID(ShaderLib.Variables.VECTOR_FOG_HORIZON);
      id_fogApexColor = Shader.PropertyToID(ShaderLib.Variables.VECTOR_FOG_APEX);
      id_skyHorColor = Shader.PropertyToID(ShaderLib.Variables.VECTOR_SKY_HORIZON);
      id_skyApexColor = Shader.PropertyToID(ShaderLib.Variables.VECTOR_SKY_APEX);
      id_params = Shader.PropertyToID(ShaderLib.Variables.VECTOR_FOG_PARAMS);
#if !UNITY_EDITOR
      ValidateSkybox();
#endif
    }
        void Awake()
        {
            if (_instance)
            {
                throw new System.Exception("Singleton Exception.");
            }
            _instance       = this;
            id_fogHorColor  = Shader.PropertyToID(ShaderLib.Variables.VECTOR_FOG_HORIZON);
            id_fogApexColor = Shader.PropertyToID(ShaderLib.Variables.VECTOR_FOG_APEX);
            id_skyHorColor  = Shader.PropertyToID(ShaderLib.Variables.VECTOR_SKY_HORIZON);
            id_skyApexColor = Shader.PropertyToID(ShaderLib.Variables.VECTOR_SKY_APEX);
            id_params       = Shader.PropertyToID(ShaderLib.Variables.VECTOR_FOG_PARAMS);
#if !UNITY_EDITOR
            ValidateSkybox();
#endif
        }