Find the limits of the parameter describing a spline curve (made using cscvn)

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Anshuman Pal 2022-2-2

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https://ww2.mathworks.cn/matlabcentral/answers/1641080-find-the-limits-of-the-parameter-describing-a-spline-curve-made-using-cscvn

回答： Anshuman Pal 2022-2-2

采纳的回答： Anshuman Pal

tempImage_spline.png

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Hello,

I am trying to interpolate a space curve in 3d using splines. This link (https://in.mathworks.com/help/curvefit/splines-in-the-plane.html) shows that the spline is parametrised by a single parameter t, and hence I can evaluate the spline curve at distinct points using fnval(curve, t). However, how do I know the limits (min and max) of this parameter t?

For example, here I plot an incomplete curve (in blue) using an arbitrary max of 100.5 (the min is 0, I presume). The entire curve is plotted in dashed red (see attached file):

curve=cscvn(xyz);
% Evaluate the spline at definite points
t = linspace(0,100.5,501);      % 100.5 is arbitrary
cv = fnval(curve, t);  
figure; hold on
fnplt(curve,'r--',2)     % plot entire spline
plot3(cv(1,:),cv(2,:),cv(3,:),'b','LineWidth',5);
view(3)

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Answer 1

Anshuman Pal 2022-2-2

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1641080-find-the-limits-of-the-parameter-describing-a-spline-curve-made-using-cscvn#answer_887570

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I found the answer! All I had to do was search in the properties of curve. So, I have to use min(curve.breaks) and max(curve.breaks)as the limits of t:

t = linspace(min(curve.breaks), max(curve.breaks),501);