nurbs曲面拟合，采用nurbs算法

clc clear close all % step1: points and knots load data_example % step 2: create the spline sp = spmak(knots,ctrlpoints'); fnplt(sp,[knots(5),knots(42)]); axis off axis equal hold on title 'you are a cow' % step 3: get points on the curve dt = knots(5):3:knots(42); p = fnval(sp,dt); plot(p(1,:),p(2,:),'.g') % step 4: get dir draw normals dp1 = fnder(sp); dp = fnval(dp1,dt); len = size(dt,2); for i = 1:len dir = dp(:,i); scale = 1/sqrt(dir(1)^2+dir(2)^2); dir = dir*scale; plot([p(1,i),p(1,i)+dir(2)],[p(2,i),p(2,i)-dir(1)],'r'); end