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Bezier Curve Function

version 1.0 (1.37 KB) by

Vectorized function to calculate Bezier Curve

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This function constructs a Bezier curve from given control points. P is a vector of control points. N is the number of points to calculate.

Example:

P = [0 0; 1 1; 2 5; 5 -1];
x = (0:0.0001:5);
y = BezierCurve(length(x), P);
plot(x, y, P(:, 1), P(:, 2), 'x-', 'LineWidth', 2); set(gca, 'FontSize', 16)

Comments and Ratings (4)

Jason Kurtz

Here is modified code that works. Note that the function now returns two sets of variables.

function [x y] = BezierCurve(N, P)
% This function constructs a Bezier curve from given control points. P is a
% vector of control points. N is the number of points to calculate.
%
% Example:
%
% P = [0 0; 1 1; 2 5; 5 -1];
% y = BezierCurve(1000, P);
% plot(x, y, P(:, 1), P(:, 2), 'x-', 'LineWidth', 2); set(gca, 'FontSize', 16)
%
% Prakash Manandhar, pmanandhar@umassd.edu

Np = size(P, 1);
u = linspace(0, 1, N);
B = zeros(N, Np);
for i = 1:Np
B(:,i) = nchoosek(Np-1,i-1).*u.^(i-1).*(1-u).^(Np-i); %B is the Bernstein polynomial value
end
S = B*P;
x = S(:, 1);
y = S(:, 2);

Gaute Hope

Yes, there is a problem with this function.

Joey

Joey (view profile)

Joey

Joey (view profile)

I don't understand the math well enough to pick out exactly what's wrong, but the curve that this code gives for certain sets of points is definitely not right.

Try this and you'll see:
P = [0 2; 4.38 6.38; 5.32 5.32; 9.7 9.7];
x = (0:0.01:9.7);
y = BezierCurve(length(x), P);
plot(x, y, P(:, 1), P(:, 2), 'x-', 'LineWidth', 2); set(gca, 'FontSize', 16)

http://img685.imageshack.us/img685/9228/badcurve.jpg

MATLAB Release
MATLAB 7.11 (R2010b)
Acknowledgements

Inspired by: Bezier Curve Plotter

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