From kde-edu-devel  Mon Jul 11 17:30:47 2005
From: Kevin Krammer <kevin.krammer () gmx ! at>
Date: Mon, 11 Jul 2005 17:30:47 +0000
To: kde-edu-devel
Subject: Re: [kde-edu]: Need help with this code
Message-Id: <200507111930.47874.kevin.krammer () gmx ! at>
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On Monday 11 July 2005 19:17, Albert Astals Cid wrote:
> Well, he really needs to rotate before translating, but that means puting
> the rotate line after the translate one due to mathematical things, that
> is, rotations and translations are done with matrix multiplications and t=
he
> fact that matrix multiplications are done =BFright to left? meants you ah=
ve
> to put them in the inverse order you want them to be applied.

As he rotates by 90 degrees it actually doesn't matter that much :)
Carsten had it mostly right, he rotated and then used the height value for =
the=20
"x" coordinate.

Anyway.

rotate() rotates around (0, 0)

Therefore my mental shortcut is
=2D make the point where you want to rotate around to the new (0, 0)
=2D rotate

No need to remember how matrix multiplications work :)

Cheers,
Kevin

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