On Wed, 11 Jul 2012 13:39:16 +1000 David Seikel <onef...@gmail.com> said:

> On Wed, 11 Jul 2012 12:03:06 +0900 Carsten Haitzler (The Rasterman)
> <ras...@rasterman.com> wrote:
> 
> > On Wed, 11 Jul 2012 11:19:20 +1000 David Seikel <onef...@gmail.com>
> > said:
> > 
> > > On Wed, 11 Jul 2012 09:40:54 +0900 Carsten Haitzler (The Rasterman)
> > > <ras...@rasterman.com> wrote:
> > > 
> > > > On Wed, 11 Jul 2012 00:59:32 +0900 Christophe Sadoine
> > > > <ch...@indefini.org> said:
> > > > 
> > > > > On 11 July 2012 00:32, Carsten Haitzler <ras...@rasterman.com>
> > > > > wrote:
> > > > > > On Tue, 10 Jul 2012 23:26:50 +0900 Christophe Sadoine
> > > > > > <ch...@indefini.org> said:
> > > > > >
> > > > > >> Hello,
> > > > > >> I just subscribed to the list today, as I was going to
> > > > > >> submit a patch. I live in Seoul and might be able to join :)
> > > > > >
> > > > > > are you french?
> > > > > 
> > > > > yes...
> > > > 
> > > > zut alors! .... le tabernac! :) where do all you french people
> > > > come from? :) sure - come along! the french cabal is growing!
> > > 
> > > Usually they come from France.  :-P
> > 
> > damn! really? it's time we put a stop to this "france" thing. it's
> > breeding all these french people i keep running into! :) :)
> > 
> > > > > I am not really working on the libraries or enlightenment.
> > > > > the patch is just a function I need but I don't think many
> > > > > people will use it... it's for rotating an evas map with a
> > > > > quaternion instead of euler angles.
> > > > 
> > > > aaarhmmm... i'm trying to think of a use for this, but my brain is
> > > > coming up blank. :)
> > > 
> > > Well, in OpenSim / SecondLife based virtual worlds, quaternions are
> > > the native format used for angles.  Probably in other 3D apps as
> > > well. Makes life easy when you are dealing with "rotate A to X,
> > > then rotate B to Y relative to A's X rotation" sort of things.  Why
> > > would that be important to UI?  Well, what happens if your UI is
> > > mapped to the surface of an object in the 3D world?  You walk
> > > around that object, it rotates, and the UI is rotated relative to
> > > the combined rotation of the object and your point of view.  The
> > > maths for that are a lot easier to deal with in quaternions than
> > > they are in euler angles.
> > 
> > ummm with euler u just apply the rotation twice. :)
> 
> And what is the difference between the maths for "apply the rotation"?
> Go look it up, also look up "gimbal lock".  There's good reasons why
> people use quaternions, it's not just some fancy maths to show you have
> a degree.

apply in another order :)

-- 
------------- Codito, ergo sum - "I code, therefore I am" --------------
The Rasterman (Carsten Haitzler)    ras...@rasterman.com


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