Symbolic representation of a Bézier curve

Question

The Bézier curve is defined by:

$$C(t)=\sum_{i=0}^{n} {{n}\choose{i}} t^i (1-t)^{n-i} P_i$$

where the $P_i$ are the control points.

I am trying to write it down in Mathematica. What I have is:

p0 = {0, 0};
p1 = {1, 1};
p2 = {2, 1};
p3 = {3, -1};
p = {p0, p1, p2, p3};

c[t_, n_] := \!\(
\*UnderoverscriptBox[\(\[Sum]\), \(i = 0\), \(n\)]\(Binomial[n, i] 
\*SuperscriptBox[\(t\), \(i\)] 
\*SuperscriptBox[\((1 - t)\), \(n - i\)] p[\([i]\)]\)\)

I can't manage to get a proper list for plotting. Can anyone please advise on how to correctly formulate the equations?

Answer 1

Here is how to manually implement a Bézier curve:

p = {{0, 0}, {1, 1}, {2, 1}, {3, -1}};
n = Length[p] - 1;

ParametricPlot[Sum[p[[i + 1]] Binomial[n, i] t^i (1 - t)^(n - i), {i, 0, n}] // Evaluate,
               {t, 0, 1}]

To compare with the built-in:

Show[%, Prolog -> {Directive[AbsoluteThickness[4], ColorData[97, 2]], BezierCurve[p]}]

Answer 2

An alternative is to use BezierFunction. Your example:

p = {{0,0},{1,1},{2,1},{3,-1}};

ParametricPlot[BezierFunction[p][t], {t, 0, 1}]