GetNURBSurf

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GetNURBSurf

Description

Gets a NURB surface from the associated FRED document.

Syntax

GetNURBSurf n, entity, maxIdxU, maxIdxV, orderU, orderV, knotU, knotV, points, weights

Parameters

n As Long

Node number of the surface.

entity As T_ENTITY

Will hold the generic entity data from the NURB surface.

maxIdxU As Long

One less than the number of terms in the U parameter direction.

maxIdxV As Long

One less than the number of terms in the V parameter direction.

orderU As Long

Returns the order of the U basis functions.

orderV As Long

Returns the order of the V basis functions.

knotU() As Double

Returns the values in the U knot array.

knotV() As Double

Returns the values in the V knot array.

points() As Double

Returns the control points as a 2 x N array, where N is the number of control points minus 1.

weights() As Double

Returns the weights of the control points.

Remarks

If there is a problem, the subroutine sets an error and returns without modifying the parameters. Note that the NURB order is given by order = degree + 1. For example, an order 3 NURB is quadratic and an order 4 NURB is cubic.

Example

Suppose that a NURB surface is defined with the parameters shown below:

The following script uses the GetNURBSurf subroutine to retrieve the surface's information and print it to the output window.

Sub Main

Dim ent As T_ENTITY

Dim nurbNode As Long, maxIdxU As Long, maxIdxV As Long, orderU As Long, orderV As Long, ii As Long, jj As Long

Dim knotU() As Double, knotV() As Double, points() As Double, weights() As Double

ClearOutputWindow

'Node number of the NURB surface being queried

nurbNode = FindFullName( "Geometry.cadgasket.Trimmed Surface 611 87.B-Spline Surface 88" )

'Retrieve the parameters of the NURB surface

GetNURBSurf nurbNode, ent, maxIdxU, maxIdxV, orderU, orderV, knotU, knotV, points, weights

'Print out NURB surface information

Print "Node Number: " & Chr(9) & nurbNode

Print "Name: " & Chr(9) & ent.name

Print "Max U Index: " & Chr(9) & maxIdxU

Print "Max V Index: " & Chr(9) & maxIdxV

Print "Order U: " & Chr(9) & orderU

Print "Order V: " & Chr(9) & orderV

'Print out U and V knot vectors in columns.

Print "Knot Vectors: " & Chr(9) & "U Knot" & Chr(9) & "V Knot"

For ii = 0 To Max( UBound( knotU, 1 ), UBound( knotV, 1 ) )

If ii <= UBound( knotU, 1 ) Then

Print Chr(9) & knotU( ii );

Else

Print Chr(9) & Chr(9);

End If

If ii <= UBound( knotV, 1 ) Then

Print knotV( ii )

Else

Print Chr(9)

End If

Next ii

'Print out control points and weights arrays. There are (maxIdxU+1)*(maxIdxV+1) control points.

'In this case the points() array has size 2 x 17.

Print "Control points and weights:

Print Chr(9) & "X" & Chr(9) & "Y" & Chr(9) & "Z" & Chr(9) & "Weight"

For ii = 0 To (maxIdxU+1)*(maxIdxV+1)-1

Print Chr(9) & points( 0, ii );

Print points( 1, ii );

Print points( 2, ii );

Print weights( ii )

Next ii

End Sub

This script prints the following information to the output window for the example NURB surface:

Node Number: 6

Name: B-Spline Surface 88

Max U Index: 1

Max V Index: 8

Order U: 2

Order V: 3

Knot Vectors: U Knot V Knot

0 0

1 0

1 0.25

0.25

0.5

0.75

Control points and weights:

X Y Z Weight

20 -55 0 1

20 -35 0 0.7071067811865

1.224646799147E-15 -35 0 1

-20 -35 0 0.7071067811865

-20 -55 0 1

-20 -75 0 0.7071067811865

-3.673940397442E-15 -75 0 1

20 -75 0 0.7071067811865

20 -55 0 1

20 -55 2 1

20 -35 2 0.7071067811865

1.224646799147E-15 -35 2 1

-20 -35 2 0.7071067811865

-20 -55 2 1

-20 -75 2 0.7071067811865

-3.673940397442E-15 -75 2 1

20 -75 2 0.7071067811865

20 -55 2 1