"vedutismo" projection?

  • Hi Klaus

    Thanks for a great viewer.

    Do you think it could handle also the new "vedutismo" (PTGui) aka "equi-perspective" (PTAssembler) aka "Pannini" (Hugin and Panini) projection? That is a kind of cylindrical stereographic projection which can make many views appear to have natural perspective even at very wide angles.

    The Panini viewer (which I wrote) can display spherical panos "live" in this projection, but uses a 3D OpenGL model to do so. I don't know if Flash can do something equivalent, but it would be great if it could. Panini is only a file viewer, so a web viewer with Pannini projection would be most welcome.

    Best Regards, Tom

  • oh, never mind I saw some examples, VERY interesting, if you wrote the paninin viewer, I downloaded it from sourforge, is it the same one?

    if so, are you planing on fixing the save as function? not fixing, but changing, it saves really well, except the compression/interpolation is bad, looks fussy :(

    anyway, hopefully Krpano will have this projection, as it looks interesting :)

  • Hi,

    yes, sound interesting!

    you said "stereographic cylindrical" - yes, that should be possible
    are there also any other transformations (any variable vertical scaling?)

    but I'm not sure how a cylindrical projection can work on spherical or cubical panos?
    and if a interpolation between other projection modes can be done...

    I'll try it a let you known

    best regards,

  • Hi Klaus

    Panini is designed to make printable views with controlled perspective, so yes, it does have several adjustments in addition to the Pannini projection. But they are most useful after the basic direction and field of view have been set, and might not be so appropriate for a rotating view.

    The basic Pannini projection, as Bruno Postle deduced it, has a simple geometrical form: first project the world onto a panocylinder (in place of the more usual panosphere). Then view the cylinder from a point on its surface, like the view of the sphere in the stereographic projection. In Panini, PTAssembler, and PTGui the distance of the viewpoint from the center of the panocylinder is actually adjustable, so one can "sweep" from rectilinear through full Pannini and beyond. This is a very useful feature, because the average randomly chosen view probably looks better with the eye about halfway from center to surface, but some views definitely deserve the full treatment.

    A Pannini image has straight verticals and also straight diagonals while being compressed horizontally (most at the edges) and expanded vertically (most in the center). The horizontal compression allows fields of view up to 200 degrees or more to look almost like normal perspective views -- provided one is looking more or less toward a strong "vanishing point", for example down a street. The vertical expansion, though required to make the diagonals straight, also makes the middle top and bottom of the view "bulge out" rather a lot, and squeezing those parts of the image generally improves its appearance . So I would say that would be a desirable feature.

    There is a Mathmap script at http://www.flickr.com/groups/vedutismo/ in the discussions that shows the mathematical form of the Pannini projection, and another that shows one way of applying top and bottom "squeezes" to make a view look almost rectilinear. Those are extreme squeezes requiring custom adjustment for each view. A useful generic squeeze is much easier to implement -- simply reduce the power of the vertical cosine function in the Pannini formula from 2 to 1 or perhaps 1.5.

    Sorry to bend your ear, but I would really love to see this projection in a widely used web pano viewer. I'm quite sure it would be popular: in my experience, at wide fields of view almost every pano looks better in a moderate Pannini projection than in the rectilinear one.

    Get Panini and see for yourself (https://sourceforge.net/projects/pvqt/).

    Regards, Tom

  • Hi,

    here is it - krpano with Pannini Projection:


    it looks really good at wide angles - a great idea Tom!

    I added a new parameter for the <view> tag - called "pannini" (possible values are "true" or "false")
    the "strongness" of the projection it is controlled via the "fisheye" (=the viewpoint distance from the center),
    the "fisheyefovlink" (=a dynamic adjustment of the "fisheye" parameter relative to the field of view) and
    the "stereographic" parameter, just like the other projections,

    I added some buttons in the example with for testing of some different settings,
    the parameters can also be changed with the options plugins (button in the right top)

    (I'll update the current download package to this version in some minutes)

    thanks Tom!

    best regards,

  • hi all,

    its great to find a good forum like on panoramic and 360 tours!

    A build mostly 360 tours and to investigate other options of image and 360 tour output is great.

    From experience though, a client can have too may options if all are shown, so i stick to just one or two. However, there will always be someone who sees an unusual output and want one.
    Also, user experience - will they have a better experience with a different projection?




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