Friday, March 2, 2018

DELPHI - How to make cubic B-Spline interpolation + Cox-De-Boora algorithmus

const giCount = 15;
      giDetail = 10;
...
procedure TForm1.BSpline_Clamped;
var
  j, i, iIndex : integer;
  iNumSegmentsCount : integer;
  iT, i1_T, iB0, iB1, iB2, iB3 : double;
  iNewX, iNewY : double;
  pSerieLine : TLineSeries;
  iValue : extended;
begin

  pSerieLine := TLineSeries( Chart1.Series[1] );
  pSerieLine.Clear;

  { draw count of cubic curves }
  for iIndex := -2 to px.Count - 2 do
    begin

       { every curve generate from I parts }
       for i := 0 to giDetail - 1 do
         begin
           iT := i / (giDetail-1);
           i1_T := 1 - iT;

           iB0 := ( i1_T * i1_T * i1_T ) / 6;
           iB1 := ( ( 3 * iT * iT * iT ) - ( 6 * iT * iT ) + 4 ) / 6;
           iB2 := ( ( -3 * iT * iT * iT ) + ( 3 * iT * iT ) + ( 3 * iT ) + 1 ) / 6;
           iB3 := ( iT * iT * iT ) / 6;

           iNewX := iB0 * GetValueX( iIndex ) +
                    iB1 * GetValueX( iIndex + 1 ) +
                    iB2 * GetValueX( iIndex + 2 ) +
                    iB3 * GetValueX( iIndex + 3 )
                    ;

           iNewY := iB0 * GetValueY( iIndex ) +
                    iB1 * GetValueY( iIndex + 1 ) +
                    iB2 * GetValueY( iIndex + 2 ) +
                    iB3 * GetValueY( iIndex + 3 );

           pSerieLine.AddXY( iNewX, iNewY );
         end;
  end;
  
end;

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