Calculates the tangency directions at the given parameter values on the curve.
| Name | Type | Description |
| Params | Double | Input/output array of Doubles that specifies the parameters. |
| UTangents | Double | Output Double array that returns the tangent vectors in the U parameter direction at the specified parameter points. |
| VTangents | Double | Output Double array that returns the tangent vectors in the V parameter direction at the specified parameter points. |