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is pitch limited by HFOV in spherical panos? RRS feed

  • Question

  • In a 360x180 pano, if I zoom out to an HFOV of 220 degrees or thereabouts, I cannot change the pitch, even though there is more image above the top of the screen.  This is strange becasue with a smaller HFOV, I can show the vertex and/or nadir (HDView seems to show a small hole at those points, but this may be my problem). 

    Is this expected behavior (not being able to change the pitch with a large HFOV) or is it something I'm doing wrong?
    Sunday, August 19, 2007 7:12 PM

Answers

  • Hello.  Yes it is limited.  As the field of view increases we force the viewing direction to the horizon and gradually limit the ability to change the pitch.  The reason we did this is related to one of your previous comments.  The equirectangular projection is fairly unfamilar to users, letting the horizon change under this projection was even more confusing.  The downside with our current implementation is that at certain field-of-views you cannot pitch to certain parts of the image.  We probably haven't yet gotten the ideal set of limits and author controlled parameters, so any suggestions for future releases are welcome.

    Sunday, August 19, 2007 9:02 PM

All replies

  • Hello.  Yes it is limited.  As the field of view increases we force the viewing direction to the horizon and gradually limit the ability to change the pitch.  The reason we did this is related to one of your previous comments.  The equirectangular projection is fairly unfamilar to users, letting the horizon change under this projection was even more confusing.  The downside with our current implementation is that at certain field-of-views you cannot pitch to certain parts of the image.  We probably haven't yet gotten the ideal set of limits and author controlled parameters, so any suggestions for future releases are welcome.

    Sunday, August 19, 2007 9:02 PM
  • Two ways to address this are:

    1. switch from a rectangular projection to another projection (one of the ones that has the top row shorter than the equator) after a (user specified) HFOV is reached by zooming.

    2. Add lines along the "latitude" and "longitude".  The user would be used to seening a globe with these lines, and they may clue them into understanding where the vertex and nadir are.  The lines may also give a good visual hint to the user that they are viewing a three dimensional sphere, and the curved horizon (assuming its on the equator) would be easier for the user to understand.  It would be nice if the lines could be toggled on and off by the user.

    3. use a circular image beyond a certain HFOV, and add lines of latitude and longitude as shown in the Azumithal projection on http://en.wikipedia.org/wiki/Map_projection.  This means that the whole image will never be seen, which may be ok for a spherical pano.

    Note that a help button on the viewer would be good.  One thing the help system should have is an example of the projections, using a map of the Earth as a reference.  A globe of Earth is very common, people understand it.  And people are comfortable with many of the two dimensional projections used to show maps of the Earth.  So this will give the public a clue about how any projections HDView implements work.

    Tuesday, August 21, 2007 2:09 PM