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Re: [PanoToolsNG] Learned from the List

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  • Roger D. Williams
    ... Thanks for the feedback, Briar. Since I see from a later post that you use DevalVR, as I do, I am not sure what you mean about the bending of verticals.
    Message 1 of 9 , May 2, 2011
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      On Tue, 03 May 2011 04:48:15 +0900, Briar <briar_bentley@...> wrote:

      > Amazing how quickly other peoples' situation goes to the back of our
      > minds.
      > The international news no longer concentrates on the efforts of the brave
      > folk who still battle with the nuclear plants in your country. But thank
      > goodness you still have somewhere like this to "rest and renew"
      >
      >
      > My question, and admiration for your pan is how you manage to set it so
      > there is no distortion when moving up or down. In most pans a building
      > will
      > "bend" towards the centre as you move higher up. In this everything
      > remains
      > vertical. How?

      Thanks for the feedback, Briar. Since I see from a later post that you use
      DevalVR, as I do, I am not sure what you mean about the "bending" of
      verticals. I have only ever seen this once with DevalVR, when I used it
      to view a panorama taken with a rotary camera that generates cylindrical
      projections by default. If you are taking cylindrical panoramas, then
      DevalVR will normally default to treating them as spherical projections,
      and this bends the verticals as you near the top and bottom of the image.

      I haven't updated DevalVR recently, so it may well be coping properly
      with cylindrical projections by now. The author kindly provided me with
      a version that DID handle them properly, but I overwrote it with a later
      upgrade that lacked this ability and as I no longer generate cylindrical
      projections I haven't done anything about it.

      Other than that I can't think what might be responsible for "bending," as
      the verticals always remain straight even as they splay outwards on
      looking up (and cave inwards on looking down, of course).

      As a matter of interest, the vertical were very hard to get right on this
      panorama, as there are very few readily identifiable true verticals...
      and mostly on rather remote sculptures.

      Roger W.

      --
      Work: www.adex-japan.com
    • Ken Warner
      Roger, you are exactly right. Cylindrical images need a cylindrical projection. Most viewers use a gnomic projection assuming that the image they are
      Message 2 of 9 , May 2, 2011
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        Roger, you are exactly right. Cylindrical images need a cylindrical
        projection. Most viewers use a gnomic projection assuming that the
        image they are projecting is a spherical image. A cylindrical image
        projected gnomically will have verticals that converge toward the poles.

        If DevalVR does handle cylindrical projections correctly, that would be a
        very good thing for architectural scenes.

        Roger D. Williams wrote:
        > On Tue, 03 May 2011 04:48:15 +0900, Briar <briar_bentley@...> wrote:
        >
        >> Amazing how quickly other peoples' situation goes to the back of our
        >> minds.
        >> The international news no longer concentrates on the efforts of the brave
        >> folk who still battle with the nuclear plants in your country. But thank
        >> goodness you still have somewhere like this to "rest and renew"
        >>
        >>
        >> My question, and admiration for your pan is how you manage to set it so
        >> there is no distortion when moving up or down. In most pans a building
        >> will
        >> "bend" towards the centre as you move higher up. In this everything
        >> remains
        >> vertical. How?
        >
        > Thanks for the feedback, Briar. Since I see from a later post that you use
        > DevalVR, as I do, I am not sure what you mean about the "bending" of
        > verticals. I have only ever seen this once with DevalVR, when I used it
        > to view a panorama taken with a rotary camera that generates cylindrical
        > projections by default. If you are taking cylindrical panoramas, then
        > DevalVR will normally default to treating them as spherical projections,
        > and this bends the verticals as you near the top and bottom of the image.
        >
        > I haven't updated DevalVR recently, so it may well be coping properly
        > with cylindrical projections by now. The author kindly provided me with
        > a version that DID handle them properly, but I overwrote it with a later
        > upgrade that lacked this ability and as I no longer generate cylindrical
        > projections I haven't done anything about it.
        >
        > Other than that I can't think what might be responsible for "bending," as
        > the verticals always remain straight even as they splay outwards on
        > looking up (and cave inwards on looking down, of course).
        >
        > As a matter of interest, the vertical were very hard to get right on this
        > panorama, as there are very few readily identifiable true verticals...
        > and mostly on rather remote sculptures.
        >
        > Roger W.
        >
      • Roger D. Williams
        On Tue, 03 May 2011 12:36:33 +0900, Ken Warner ... Yes, and there s a fairly easy (though not universally applicable) way of
        Message 3 of 9 , May 2, 2011
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          On Tue, 03 May 2011 12:36:33 +0900, Ken Warner <kwarner000@...>
          wrote:

          > Roger, you are exactly right. Cylindrical images need a cylindrical
          > projection. Most viewers use a gnomic projection assuming that the
          > image they are projecting is a spherical image. A cylindrical image
          > projected gnomically will have verticals that converge toward the poles.
          >
          > If DevalVR does handle cylindrical projections correctly, that would be a
          > very good thing for architectural scenes.

          Yes, and there's a fairly easy (though not universally applicable) way
          of differentiating between cylindrical and spherical projections. If
          the image has a width that is exactly double the height, then it is
          usually safe to assume "spherical" and if not, well, not.

          Roger W.

          --
          Work: www.adex-japan.com
        • fierodeval
          Hi Roger, Yes, DevalVR works as you wrote, if the proportion is aproximately 2:1 the projection used is spherical , if not it uses cylindrical , this is true
          Message 4 of 9 , May 3, 2011
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            Hi Roger,

            Yes, DevalVR works as you wrote, if the proportion is aproximately 2:1 the projection used is "spherical", if not it uses "cylindrical", this is true in 99% of cases. Maybe the stitching program could add an EXIF code to solve this ambiguity in the JPEG, I don't know.

            Anyway, I added the projection options in the context menu of the player since one year ago, so projection can be changed easily.

            regards!
            fiero




            --- In PanoToolsNG@yahoogroups.com, "Roger D. Williams" <roger@...> wrote:
            >
            > On Tue, 03 May 2011 12:36:33 +0900, Ken Warner <kwarner000@...>
            > wrote:
            >
            > > Roger, you are exactly right. Cylindrical images need a cylindrical
            > > projection. Most viewers use a gnomic projection assuming that the
            > > image they are projecting is a spherical image. A cylindrical image
            > > projected gnomically will have verticals that converge toward the poles.
            > >
            > > If DevalVR does handle cylindrical projections correctly, that would be a
            > > very good thing for architectural scenes.
            >
            > Yes, and there's a fairly easy (though not universally applicable) way
            > of differentiating between cylindrical and spherical projections. If
            > the image has a width that is exactly double the height, then it is
            > usually safe to assume "spherical" and if not, well, not.
            >
            > Roger W.
            >
            > --
            > Work: www.adex-japan.com
            >
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