Geometry Boost List: [ggl] Efficient rotation about a point

Subject: [ggl] Efficient rotation about a point
From: Mateusz Loskot (mateusz)
Date: 2009-12-01 14:07:14

Barend Gehrels wrote:
> 
> 
> 
>>>> Barend, since GGL transformers aren't composable, wouldn't it be 
>>>> right for GGL to provide some type of transformer taking a matrix as 
>>>> its constructor parameter?
>>>
>>> Yes, I think that is a good idea. Will be solved (either done, or 
>>> maybe they should be composable).
>>
>> I was thinking about it yesterday.
>>
>> For now, wouldn't it be sufficient to use ublas_transformer
>> and enable compositions [1] with a simple custom matrix [2] in similar 
>> manner as Boost.GIL does it.
>>
>> [1] http://www.boost.org/doc/libs/1_41_0/libs/gil/example/affine.cpp
>> [2] 
>> http://www.koders.com/cpp/fidEE0E20E57D2E5FCE4EE30F3AF143F5E78A7749B3.aspx 
>>
>>
> 
> Interesting! I didn't know that GIL defined its own matrix. That the 
> link is broken, it refers to extensions not being there (so therefore 
> [2]). Which shows the potential fragility of extensions.

I've attached affine.hpp file.
It comes from numeric extension available here:

http://opensource.adobe.com/wiki/display/gil/Contribute+to+GIL

but it looks the numeric.zip file vanished there too.
Anyway, i found this file, probably older version, at koders.com.

> It is a good idea but I don't think we can or should copy this exactly 
> because we cannot rely on external sources. Anyway, we can implement it 
> using an uBlas matrix, or include it as an example (actually, that *is* 
> the way GIL does it.... So right...)

That's right, we can just copy, refine and provide it for users who
need it now, as an extension or example, whatever.

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net
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