# Hot to use CreateSplinesByEqnParams2 with Periodic = 1?

Question asked by Thomas Samoht on Nov 15, 2014
Latest reply on Nov 22, 2014 by Thomas Samoht

Hello,

i try to biuld a closed spline using CreateSplinesByEqnParams2.

I consider following rules, applying for closed spline curves:

1) my first n control points are the same than the n last control points (where n is the order)

2) the first n knot values intervals are the same that the last n knot values intervals

3) periodic is set to "1"

4) the knot vector has ControlPointsCount + 1 values

However, the CreateSplinesByEqnParams2 method fails to biuld the spline.

What did i do wrong?

Here is a simple example (VBA):

' 1

arrCtrlPts(0) = 0

arrCtrlPts(1) = 0

arrCtrlPts(2) = 0

' 2

arrCtrlPts(3) = 0

arrCtrlPts(4) = 2

arrCtrlPts(5) = 0

' 3

arrCtrlPts(6) = 2

arrCtrlPts(7) = 2

arrCtrlPts(8) = 0

' 4

arrCtrlPts(9) = 2

arrCtrlPts(10) = 0

arrCtrlPts(11) = 0

' 5

arrCtrlPts(12) = 2

arrCtrlPts(13) = -2

arrCtrlPts(14) = 0

' 6

arrCtrlPts(15) = 0

arrCtrlPts(16) = 0

arrCtrlPts(17) = 0

' 7

arrCtrlPts(18) = 0

arrCtrlPts(19) = 2

arrCtrlPts(20) = 0

' 8

arrCtrlPts(21) = 2

arrCtrlPts(22) = 2

arrCtrlPts(23) = 0

arrKnotPts(0) = 0

arrKnotPts(1) = 0.2

arrKnotPts(2) = 0.3

arrKnotPts(3) = 0.4

arrKnotPts(4) = 0.5

arrKnotPts(5) = 0.6

arrKnotPts(6) = 0.7

arrKnotPts(7) = 0.8

arrKnotPts(8) = 1