#### ComputeDerivatives Method

Returns the vectors describing the curve at the specified parameter.

Namespace: Autodesk.Revit.DB
Assembly: RevitAPI (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0)

# Syntax

C#
``````public Transform ComputeDerivatives(
double parameter,
bool normalized
)``````
Visual Basic
``````Public Function ComputeDerivatives ( _
parameter As Double, _
normalized As Boolean _
) As Transform``````
Visual C++
``````public:
Transform^ ComputeDerivatives(
double parameter,
bool normalized
)``````

#### Parameters

parameter
Type: System Double
The parameter to be evaluated.
normalized
Type: System Boolean
If false, param is interpreted as natural parameterization of the curve. If true, param is expected to be in [0,1] interval mapped to the bounds of the curve. Setting to true is valid only if the curve is bound.

#### Return Value

The transformation containing the point on the curve, the tangent vector, derivative of tangent vector, and bi-normal vector.

# Remarks

The following is the meaning of the transformation members: Origin is the point on the curve (equivalent to Evaluate(Double, Boolean) ).BasisX is the tangent vector (the first derivative).BasisY is the second derivative. Note that for curves where this cannot be uniquely determined (e.g. lines), this will be a Zero vector.BasisZ is the bi-normal vector (tangent x normal). Note that for curves where normal cannot be uniquely determined (e.g. lines), this will be a Zero vector. None of the vectors are normalized.

# Exceptions

Exception Condition
Autodesk.Revit.Exceptions ArgumentException The given value for parameter is not finite
Autodesk.Revit.Exceptions ArgumentOutOfRangeException The curve cannot be evaluated as normalized because it is unbound. -or- The parameter is not a valid value for normalized evaluation.