[Kstars-devel] Kstars-devel Digest, Vol 143, Issue 3

[M.S. Adityan]

Hi Alexander,

Yes, what you pointed out definitely needs to be corrected. Also, the
constellation image moves when you pan the sky. I am not sure on an exact
mathematical solution to the problem. So what I have done is that I looked
up the coordinates for the midpoint of the image from Stellarium, and
adjusted the size of the image and position angle in order to best fit the
constellation lines. Now as it turns out, these values are not the same for
all projection systems.

I have tried to implement a completely new method, that fixes the 4 corners
of the rectangle in the sky, but it draws the image in a very weird manner.
The image is stretched and drawn outside the sphere. I have tried to do
this on Ursa Major. Could you perhaps suggest some ideas to solve this
problem or maybe some ideas to modify the old code itself?

Thanks.


M.S.Adityan
Website: www.msadityan.com
https://www.linkedin.com/in/msadityan

On Tue, Jul 21, 2015 at 10:36 PM, M.S. Adityan <msadityan at gmail.com> wrote:

> Hi,
>
> Here are a few proposed ideas to solve the clipping problem with
> constellation art.
>
> 1. Draw a opaque black rectangle with a hollow center for the sphere. This
> black rectangle will cover any 'part' of the constellation image that is
> drawn beyond the sphere.
>
> 2. Note down the coordinates of the 4 corners of the rectangle for each
> constellation image. Then draw the image ONLY if all the 4 corners are
> visible on the sky. This will ensure that the image is drawn only if the
> entire rectangle lies on the sky.
>
> 3. The clipping happens when FOV>180. So we get FOV center() and then find
> the minimum and maximum values by adding or subtracting 90 from it. Then
> check the midpoint Aziumth and add the width of the constellation image in
> degrees to it. If this value is greater than fov_center+90 or less than
> fov_center-90 then it needs to be clipped.
>
> Can anyone help solve this issue?
>
> Thanks.
>
> M.S.Adityan
> Website: www.msadityan.com
> https://www.linkedin.com/in/msadityan
>
> On Sat, Jul 18, 2015 at 5:30 PM, <kstars-devel-request at kde.org> wrote:
>
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>> Today's Topics:
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>>    1. Clipping artwork on the border of skymap (M.S. Adityan)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Fri, 17 Jul 2015 21:25:01 +0530
>> From: "M.S. Adityan" <msadityan at gmail.com>
>> To: KStars Development Mailing List <kstars-devel at kde.org>
>> Subject: [Kstars-devel] Clipping artwork on the border of skymap
>> Message-ID:
>>         <CA+T53Rq-pXzfJeetiDbsyw3K=k22FaOBBHOxKRp8gqC6w-v=
>> 3w at mail.gmail.com>
>> Content-Type: text/plain; charset="utf-8"
>>
>> Hi,
>>
>> I have completed Western and Inuit sky culture artwork in KStars. The
>> artwork is currently displaying completely on the border of the sky map. I
>> want to make it clip such that it displays only the portion of the artwork
>> which is "on" the sky map and not the one that goes out of the sphere. How
>> can this be achieved? To see how KStars looks currently please see this
>> <http://www.msadityan.com/wp-content/uploads/2015/07/kstars.png>.
>>
>> Also another issue was regarding pixelation of the artwork at high zoom
>> levels. To solve this, I scaled every constellation image to 1024x1024
>> pixels using Qt::SmoothTransformation. Is this a right way to solve the
>> problem? (please refer to the latest git commit on
>> gsoc2015-constellationart branch for this)
>>
>> Regards
>> M.S.Adityan
>> Website: www.msadityan.com
>> https://www.linkedin.com/in/msadityan
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>> End of Kstars-devel Digest, Vol 143, Issue 3
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