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Feature request: more sky, less landscape (horizon elevation)

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Anonymous
2014-03-28
2014-03-29

  • Anonymous
    2014-03-28

    I hereby like to bring up an idea (feature request) which was originally requested here:

    http://sourceforge.net/p/stellarium/discussion/278769/thread/f3ec2c36/

    I know that there are not so many users who commented on it but until now all people were in favor of this idea. I really think it would be an improvement and an asset! Therefore, I think it's worth for developers to look into it...

    Thanks
    Trost

     
  • barrykgerdes
    barrykgerdes
    2014-03-28

    This is a very common request. It is to do with how a spherical surface is projected onto a plane surface. If you change the focus of your view to a point above or below the horizon this will be your new horizon and the rest of the sphere will need to be distorted to accommodate this.

    There are a number of ways that the inside of a sphere can be displayed in Stellarium. These alternative projections can be found in the markings section of the viewing options menu. The stereographic ( the default projection with a FOV of 60 degrees) projection gives the most natural view of the sky as the eye sees it. This of course curves the horizon if you make the focus of your view a point above the horizon.

    Each of the projections has a special feature on the display for depicting the sky on a plane surface. If you wish to see a view where the land horizon remains the focus of view and can be moved up and down the screen while remaining a straight line try the perspective projection. This will keep the horizon level while distorting the rest of the display to suit. The wider the FOV the more distorted the outer regions of the display will become.

    Thus if you need to have the horizon "flat" at the bottom of your screen you will need the perspective projection and accept the distortion that results. The stereographic projection will always curve the screen away from the point of focus (screen centre) and cannot be changed.

    Barry

     

  • Anonymous
    2014-03-28

    Hi Barry,

    thanks first of all for your explanation. The different projection types within Stellarium are noted. Nobody doubts that all the maths & physics behind all these projections are correct and working.

    Did you have a look at the pictures attached to the original post? There is a mock-up of the desired view which was created in Photoshop. To me, this effect can be achieved imagining this:

    Set the projection to stereographic view and have your horizon set to the center of the screen being a straight line.

    1) Now imagine you are being lifted straight up by a couple of meters. Since the celestial sphere is very far away the lifting of several meters will not effect the view of the stars/celestial sphere. The horizon panorama on the contrary will change significantly as the viewer is very close to it. As we are being lifted upwards, the panorama will apparently move downwards and leaving our field of view (Note: we are still in stereographic mode)

    If you don't agree with this, imagine a different scenario:
    Again, set the projection to stereographic view and have your horizon set to the center of the screen so as to view 50% landscape and 50% sky and the horizon being a straight line. Without any movement of the camera (no tilting, turning etc.):

    2) Imagine now that you are able to enlarge your computer screen upwards (or just assume you are now enabling a second screen on top of your current screen). The (still) image would not be cut off at the upper edge of the screen but would continue (into the next screen). Having the additional view (no change in projection; distortion applies to the whole picture) just imagine you are now "cropping" your field of view by "cutting off" some of the horizon panorama on the bottom and keeping the additional view above the original screen. As the lower part of the (still) image in the lower screen is now cut off, the whole image may now be scrolled down so that the additional view of the upper screen will move into the lower screen (again, no change in projection, distortion still applies to the whole picture). The upper screen can now be imagined to be turned off and the desired view is achieved.

    Don't see this desired view to be a different projection type but rather see it a "cropping" of your field of view.

    Looking at the faked (desired) view I really think this would be a great feature and a more efficient use of the screen.

    I hope I could be of any help understanding the desired view.

    Regards
    Trost

     
    • Bogdan Marinov
      Bogdan Marinov
      2014-03-29

      Don't see this desired view to be a different projection type but rather see it a "cropping" of your field of view.

      We already have that. It's called "zoom". :)

       
  • barrykgerdes
    barrykgerdes
    2014-03-29

    Hi Trost
    It all sounds nice and your idea has been suggested many times. However the screen display just does not work that way. The only way to have the land offset from the screen horizon and stay a straight line is to use the perspective view or zoom in like Bogdan says to the point where the curve of the land is not noticed.

    Barry

     


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