Swizzling (computer graphics)

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In computer graphics, swizzling means rearranging the elements of a vector[1]. For example, if A = {1,2,3,4}, you could swizzle A to get B = A.wwxy, then B would equal {4,4,1,2}. This is common in GPGPU applications.

In terms of linear algebra, this is equivalent to multiplying by a matrix of zeros and ones such that each row has exactly one one. If $A = (1,2,3,4) T$ , then swizzling $A$ as above looks like

$A.wwxy = \begin{bmatrix} 0&0&0&1 \\ 0&0&0&1 \\ 1&0&0&0 \\ 0&1&0&0 \end{bmatrix}\begin{bmatrix} 1\\ 2\\ 3\\ 4\end{bmatrix} = \begin{bmatrix} 4\\ 4\\ 1\\ 2\end{bmatrix}$ .