GetTangents Method

Description

Computes the two unit-vector tangents, given an array of parametric points on the surface.

Syntax

Visual Basic
Public Sub GetTangents( _ ByVal NumParams As Long, _ ByRef Params() As Double, _ ByRef UTangents() As Double, _ ByRef VTangents() As Double _ )

Parameters

NumParams: Specifies the number of points to be evaluated.
Params: Returns the array of parametric points at which to evaluate the surface tangents.
UTangents: Returns the array of unit tangent vectors in the direction of increasing u. Can be NULL if only v-tangents are required.
VTangents: Returns the array of unit tangent vectors in the v direction, governed by the right-hand rule. Can be NULL if only u-tangents are required.

Remarks

This method computes the two unit-vector tangents in the u and v direction at each of the points, given an array of parametric points (u, v) on the surface. The tangent in the u-direction is always pointed in the direction of increasing u value. But the tangent in the v-direction is given by the cross-product between the Face normal and the U-tangent. This satisfies the right-hand rule for a triad formed with the u-tangent, v-tangent, and the Face-normal, respectively.

Example

Example (Visual Basic)

Private Sub Form_Load()
    Dim objApp As solidedgeframework.Application
    Dim objDoc As SolidEdgepart.PartDocument
    Dim objBody As solidedgegeometry.Body
    Dim objFace As solidedgegeometry.Face
    Dim dblParam(3) As Double
    Dim dblUTangents() As Double
    Dim dblVTangents() As Double
    Const TESTFILE = "T:\vbtests\testcases\HalfCyl.par"
    ' Report errors
    Const PI = 3.14159265358979
    ' Create/get the application with specific settings
    On Error Resume Next
    Set objApp = GetObject(, "SolidEdge.Application")
    If Err Then
        Err.Clear
        Set objApp = CreateObject("SolidEdge.Application")
        Set objDoc = objApp.Documents.Add("SolidEdge.PartDocument")
        objApp.Visible = True
    Else
        Set objDoc = objApp.ActiveDocument
    End If
    Call objDoc.Close
    ' opening the testfile
    Set objDoc = objApp.Documents.Open(TESTFILE)
    ' getting the body object of the model
    Set objBody = objDoc.Models(1).Body
    ' getting a particular face from the collection of faces on the body
    Set objFace = objBody.Faces(FaceType:=igQueryAll).Item(2)
    ' getting the tangents at a point (the minimum & maximum parameters found using GetParamRange method) on a Face
    dblParam(0) = PI / 2
    dblParam(1) = 0.05
    dblParam(2) = 3 * PI / 2
    dblParam(3) = 0.1
    Call objFace.GetTangents(NumParams:=2, Params:=dblParam, UTangents:=dblUTangents, _
                             VTangents:=dblVTangents)
    ' USER DISPLAY
    ' Release objects
    Set objApp = Nothing
    Set objDoc = Nothing
    Set objBody = Nothing
    Set objFace = Nothing
End Sub