4 x 4 or 3 x 4 format?

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I have a 3 x 4 matrix of -R|t information. Seems fine. However I came across an exercise where a bottom layer of '0 0 0 1' was added across the bottom of said matrix. For me to change this would create a cascading change effect on every matrix dependent on it. What should I be doing?

Which is the correct configuration 4 x 4

[0 1 0 tx;

1 2 1 ty

1 1 2 tz

0 0 0 1]

or

3 x 4

[0 1 0 tx

1 2 1 ty

1 1 2 tz]

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