3D line approximation (spline)

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Hongying LI
Hongying LI on 21 Feb 2011
Hi everyone,
How can we use "spline" to approximate a sequence of points in three dimension rather than interpolate?
  2 Comments
Hongying LI
Hongying LI on 21 Feb 2011
I do look for a "approximation" method for a line in "3D".(I have done the interpolation)
Hongying LI
Hongying LI on 22 Feb 2011
% choose the number of pieces
pieces = 3;
s = cumsum([0;sqrt(diff(x(:)).^2 + diff(y(:)).^2 + diff(z(:)).^2)]);
pp1 = splinefit(s,xyz,pieces);
xyz1 = ppval(pp1,s);

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Answers (1)

Bruno Luong
Bruno Luong on 21 Feb 2011
  4 Comments
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Hongying LI
Hongying LI on 21 Feb 2011
Thanks Bruno,
This is my previous codes:
function newCurve = spline3dCurveInterpolation(curve, dt)
% interpote a 3d curve using spline
% path 3*x
% newPath 3*x
x = curve(1, :);
y = curve(2, :);
z = curve(3, :);
t = cumsum([0;sqrt(diff(x(:)).^2 + diff(y(:)).^2 + diff(z(:)).^2)]);
sx = spline(t,x);
sy = spline(t,y);
sz = spline(t,z);
tt = t(1):dt:t(end);
xp = ppval(sx, tt);
yp = ppval(sy, tt);
zp = ppval(sz, tt);
newCurve = [xp; yp; zp];
% end of function
Now, I'm thinking about the approximation and I don't want the line strictly pass the original points.(maybe I still don't understand your answer)
Bruno Luong
Bruno Luong on 21 Feb 2011
Did you try the FEX file (try the first one) above? They are approximation (fitting) not interpolation, exactly as your request if I'm not mistaken.

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