That exactly what I guessed. But it isn't true. If it was, a rotated map at 45°, is represented by an extent having de double of the initial size extent. A 600x600 (360000 pixels) rotated image correspond to a 848x848 (~720000) normal image. But the rotated image take 0.21s, and the normal image take 0.32s. The difference is huge.<br>
So I read the part of the source code which is responsible of rotation. There's nothing about this. And i don't find the solution to this (I don't undestund the rotation algorithm too).<br><br><br><div class="gmail_quote">
2011/4/21 thomas bonfort <span dir="ltr"><<a href="mailto:thomas.bonfort@gmail.com">thomas.bonfort@gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Mohamed,<br>
I'm guessing that as the underlying data drivers only accept<br>
rectangular extents oriented northwards, they have to return more data<br>
if there is a rotation implied. And mapserver also has to filter the<br>
extra features out at some point, even if they do not fall on the<br>
final map image. This could explain the overhead.<br>
<font color="#888888"><br>
--<br>
thomas<br>
<br>
2011/4/21 Mohamed Saâd HESSANE <<a href="mailto:saad.hessane@gmail.com">saad.hessane@gmail.com</a>>:<br>
</font><div><div></div><div class="h5">> I don't think so. If it was, juste when a cos or a sin vanish.<br>
> My first thought was that mapserver have to calculate more pixels in a<br>
> rotated map than a normale map. But when i read the source code i found that<br>
> it's the projection which rotate, not the map. So why this discimination?<br>
> The same projection<br>
><br>
><br>
> 2011/4/21 Stephen Woodbridge <<a href="mailto:woodbri@swoodbridge.com">woodbri@swoodbridge.com</a>><br>
>><br>
>> On 4/21/2011 10:32 AM, Mohamed Saād HESSANE wrote:<br>
>>><br>
>>> Hy list,<br>
>>> I have a question. I'm doing a benchmarking test of a rotated map, and i<br>
>>> get the result in the attached file.<br>
>>> My question is why it take more time to draw a map rotated at 45° than a<br>
>>> map rotated at 90° or 183° ???<br>
>>> Thank you !<br>
>><br>
>> I'm only guessing here but could it be that the math required to compute<br>
>> cos and sin is more costly in cpu cycles at those angles.<br>
>><br>
>> Regardless, this is an interesting question and I love the graphic, nice<br>
>> job on that.<br>
>><br>
>> -Steve W<br>
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</div></div></blockquote></div><br>