What is the analytical expression to do a change of basis from the extended polynomial form i.e.
$$ \mathbf {B} (t)=\sum _{j=0}^{n}{t^{j}\mathbf {C} _{j}} $$
to a Bezier form
$$ \mathbf{B} (t) =\sum _{i=0}^{n}{n \choose i}(1-t)^{n-i}t^{i} \mathbf{P} _{i}$$
where $\mathbf{P} _{i}$ are the control points and we know the relation
$$\mathbf{C} _{j}={\frac {n!}{(n-j)!}}\sum _{l=0}^{j}{\frac {(-1)^{l+j}\mathbf {P} _{l}}{l!(j-l)!}}$$
so what has to be done is to solve the following system for $\mathbf{P}$
\begin{gather}
\begin{bmatrix} \mathbf{C}_0 \\
\vdots \\
\mathbf{C}_j \\
\vdots \\
\mathbf{C}_n \end{bmatrix} = AB \begin{bmatrix} \mathbf{P}_0 \\
\vdots \\
\mathbf{P}_j \\
\vdots \\
\mathbf{P}_n \end{bmatrix}
\end{gather}
where $A\in \mathcal{M}_{n\times n}(\mathbb{R})$ is defined by
\begin{align} A_{ij} =& \frac{n!}{(n-i)!} &\mbox{ if }i=j \\
& 0 &\mbox{ sinon}
\end{align}
and $B \in \mathcal{M}_{n\times n}(\mathbb{R})$ is defined by
\begin{align} B_{ij} =& \frac{(-1)^{i+j}}{i!(j-i)!} &\mbox{ if }i\geq j \\
& 0 &\mbox{ sinon}
\end{align}
an then $(AB)^{-1}$ will be the matrix to change the basis, anyone knows the analytical value for $(AB)^{-1}$?
2026-03-26 03:11:29.1774494689
go from an extended polynomial to a Bezier polynomial
59 Views Asked by Bumbble Comm https://math.techqa.club/user/bumbble-comm/detail At
1
See section 7 of these notes:
https://www.uio.no/studier/emner/matnat/math/MAT-INF4160/h15/undervisningsmateriale/bezier1.pdf
Or section 3.3 of these notes:
http://hdl.lib.byu.edu/1877/2822