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List:       kstars-devel
Subject:    Re: [Kstars-devel]
From:       Khudyakov Alexey <alexey.skladnoy () gmail ! com>
Date:       2009-11-10 19:36:17
Message-ID: 200911102236.17233.alexey.skladnoy () gmail ! com
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> IMO if it could be only used in toScreen it won't pay off. It slows down
> SkyPoint increase memory consumption and make code more difficult to
>  understand. In best circumstances we could win at most few percents.
> 
After further examination of profiling results I can say that quaternions could 
not lead to significant perfomance improvements. 

SkyMap::toScreen takes ~10% of drawing time. Half of this time is subject to 
optimization with quaternions. Let's say they could give 2-fold win which 
means ~2.5% reduction of execution time. However overhead of keeping 
quaternion in sync is ~2.5% too.

This means that quaternions should be used if and only if they lead to more 
clean and concise code.
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