Talk:Quaternions and spatial rotation: Difference between revisions

Revision as of 17:55, 8 October 2024

Revision as of 18:19, 8 October 2024

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I believe when written as four numbers, it is relatively common to write them with the cosine term last, ie it is a 3-vector containing the axis multiplied by sin/2, followed by cos/2. This lines up the vector with 3-space vectors written in homogenous coordinates, making it very popular in code that already has to deal with those. Anybody know if there is any real convention to do it this way, and/or the way shown in the article with the cos term first? [[User:Spitzak|Spitzak]] ([[User talk:Spitzak|talk]]) 17:55, 8 October 2024 (UTC)

:In many contexts, quaternions are written as the sum of four parts in a specific order: the real part, the i part, the j part, and the k part. That form carries over to having the cosine be first, and is the one that I am most familiar with. If you've seen it the other way ... then there are (at least) two ways to do it. If this is a vote, I vote for having the {{math|cos}} term first. —[[User:Quantling|<span class="texhtml"><i>Q</i></span>uantling]]&nbsp;([[User talk:Quantling|talk]]&nbsp;&#124;&nbsp;[[Special:Contributions/Quantling|contribs]]) 18:19, 8 October 2024 (UTC)