Talk:Quaternion

Order of multiplication

In LSL, quaternion multiplication is written down in reverse order as in maths :

  Q2 * Q1   (LSL)

is the same as

  Q1 . Q2    (maths)

Perharps that would deserve a word of explanation here.

-- Catherine Pfeffer, 2007-12-08

It's probably an artifact of LSL having the operator operands reversed and they forgot to reverse them to not match the execution order. For that to make sence you need to know that in most systems when you do (a * b), a is put on the stack before b. In LSO, b is put on the stack before a. If a and b are functions, b is executed before a. Meaning, LSL uses right to left parsing execution. -- Strife Onizuka 08:48, 8 December 2007 (PST)

Yes, most probably. I filed a jira issue against this, where I cited your thoughts, I hope you don't mind. I suggest we wait for the jira issue to be processed to see if that has to be mentioned in the doc. Catherine Pfeffer, 2007-12-09

I don't mind. Thats not how wikis works, if something is wrong in the documentation (and you feel motivated) you fix it. -- Strife Onizuka 10:14, 9 December 2007 (PST)

Rotation direction in the schemas

This text has two shemas at the end. If you look well at it, the 90° rotation in the first schema and in the second schema are supposed to be opposite (once in z direction, the other time in -z direction) but the pink arrow materializing the rotation is the same.

It's the first schema that is correct (LSL follows right-hand rule for direction of positive rotations).

-- Catherine Pfeffer, 2007-12-07

That is correct, LSL uses right-hand rule set. -- Strife Onizuka

So what do we do to fix this page? Will you or someone else redraw the second schema, Strife? Catherine Pfeffer, 2007-12-09

I don't have the firmest grasp on quaternions. You could say I have a layman's understanding of them. I know how to use them and the general theory but the specifics are a bit over my head. I don't care to at this time put in the amount of work it would require. -- Strife Onizuka 10:22, 9 December 2007 (PST)

I'm very bad at computer graphics. I also hesitate in undoing someone else's work. That's why I resent doing that job myself. Catherine Pfeffer 11:12, 9 December 2007 (PST)

Dear folks: I gather by "schemas" you refer to the GIF figures. In the second figure, I was just trying to illustrate that different rotation paths taking the same direction axis to the same result can given different resulting orientations for the coordinate axes. I didn't necessarily mean to imply that the rotations were to be interpreted as positive angles. However, upon reflection -- that's a symmetry group joke! -- I agree that the result is a bit confusing. (Maybe I shouldn't do the diagrams while watching my son's Tae Kwon Do class.) I will see if I can find time to clean up the diagram and re-post it. Thanks for pointing this out, and generally for editing the text for better correspondence with SL conventions. -- Zeno Rasmuson, 12/30/07.