A quartic Bézier curve is determined by five control points,

\({{\bf{p}}_{\bf{o}}}{\bf{,}}\,{\rm{ }}{{\bf{p}}_{\bf{1}}}\,{\bf{,}}{\rm{ }}{{\bf{p}}_{\bf{2}}}\,{\bf{,}}{\rm{ }}{{\bf{p}}_{\bf{3}}}\)and \({{\bf{p}}_4}\):

\({\bf{x}}\left( t \right) = {\left( {1 - t} \right)^4}{{\bf{p}}_0} + 4t{\left( {1 - t} \right)^3}{{\bf{p}}_1} + 6{t^2}{\left( {1 - t} \right)^2}{{\bf{p}}_2} + 4{t^3}\left( {1 - t} \right){{\bf{p}}_3} + {t^4}{{\bf{p}}_4}\)for \(0 \le t \le 1\)

Construct the quartic basis matrix \({M_B}\) for \({\bf{x}}\left( t \right)\).

Short Answer

Expert verified

The quartic basis matrix is \({M_B} = \left( {\begin{array}{{}}1&{ - 4}&6&{ - 4}&1\\0&4&{ - 12}&{12}&{ - 4}\\0&0&6&{ - 12}&6\\0&0&0&4&{ - 4}\\0&0&0&0&1\end{array}} \right)\).

Step by step solution

01

Step 1:Write vector of weights of \({\bf{x}}\left( t \right)\)

The weighted vector of \({\rm{x}}\left( t \right)\) is shown below:

\(\left( {\begin{array}{{}}{1 - 4t + 6{t^2} - 4{t^3} + {t^4}}\\{4t - 12{t^2} + 12{t^3} - 4{t^4}}\\{6{t^2} - 12{t^3} + 6{t^4}}\\\begin{array}{l}4{t^3} - 4{t^4}\\\,\,\,\,\,\,\,\,\,\,{t^4}\end{array}\end{array}} \right)\)

02

Step 2:The weighted vector

Factor the weighted vector as\({M_B}{\bf{u}}\left( t \right)\), where\({\bf{u}}\left( t \right)\)is the column vector involving ascending powers of t as shown below:

\({M_B}u\left( t \right) = \left( {\begin{array}{{}}1&{ - 4}&6&{ - 4}&1\\0&4&{ - 12}&{12}&{ - 4}\\0&0&6&{ - 12}&6\\0&0&0&4&{ - 4}\\0&0&0&0&1\end{array}} \right)\left( \begin{array}{l}1\\t\\{t^2}\\{t^3}\\{t^4}\end{array} \right)\)

03

Compare and write \({M_B}\)

Thus, the vector is \({M_B} = \left( {\begin{array}{{}}1&{ - 4}&6&{ - 4}&1\\0&4&{ - 12}&{12}&{ - 4}\\0&0&6&{ - 12}&6\\0&0&0&4&{ - 4}\\0&0&0&0&1\end{array}} \right)\).

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Most popular questions from this chapter

Question: 25. Let \(p = \left( \begin{array}{l}1\\1\end{array} \right)\). Find a hyperplane \(\left( {f:d} \right)\) that strictly separates \(B\left( {0,3} \right)\) and \(B\left( {p,1} \right)\). (Hint: After finding \(f\), show that the point \(v = \left( {1 - .75} \right)0 + .75p\) is neither in \(B\left( {0,3} \right)\) nor in \(B\left( {p,1} \right)\)).

Question: In Exercises 15-20, write a formula for a linear functional f and specify a number d, so that \(\left( {f:d} \right)\) the hyperplane H described in the exercise.

Let H be the plane in \({\mathbb{R}^{\bf{3}}}\) spanned by the rows of \(B = \left( {\begin{array}{*{20}{c}}{\bf{1}}&{\bf{3}}&{\bf{5}}\\{\bf{0}}&{\bf{2}}&{\bf{4}}\end{array}} \right)\). That is, \(H = {\bf{Row}}\,B\). (Hint: How is H is related to Nul B?see section 6.1.)

In Exercises 1-4, write y as an affine combination of the other point listed, if possible.

\({{\bf{v}}_{\bf{1}}} = \left( {\begin{aligned}{*{20}{c}}{\bf{1}}\\{\bf{2}}\\{\bf{0}}\end{aligned}} \right)\), \({{\bf{v}}_{\bf{2}}} = \left( {\begin{aligned}{*{20}{c}}{\bf{2}}\\{ - {\bf{6}}}\\{\bf{7}}\end{aligned}} \right)\), \({{\bf{v}}_{\bf{3}}} = \left( {\begin{aligned}{*{20}{c}}{\bf{4}}\\{\bf{3}}\\{\bf{1}}\end{aligned}} \right)\), \({\bf{y}} = \left( {\begin{aligned}{*{20}{c}}{ - {\bf{3}}}\\{\bf{4}}\\{ - {\bf{4}}}\end{aligned}} \right)\)

The conditions for affine dependence are stronger than those for linear dependence, so an affinely dependent set is automatically linearly dependent. Also, a linearly independent set cannot be affinely dependent and therefore must be affinely independent. Construct two linearly dependent indexed sets\({S_{\bf{1}}}\)and\({S_{\bf{2}}}\)in\({\mathbb{R}^2}\)such that\({S_{\bf{1}}}\)is affinely dependent and\({S_{\bf{2}}}\)is affinely independent. In each case, the set should contain either one, two, or three nonzero points.

Question: 20. Let \(f:{\mathbb{R}^n} \to {\mathbb{R}^m}\) is a linear transformation, and let \(T\) be an affine subset of \({\mathbb{R}^{\bf{m}}}\), and let \(S = \left\{ {{\bf{x}} \in {\mathbb{R}^n}\,:\,f\left( {\bf{x}} \right) \in T} \right\}\). Show that \(S\) is an affine subset of \({\mathbb{R}^m}\).

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