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24238Re: [PanoToolsNG] Re: Pano2VR makes different default cubefaces

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  • Thomas Rauscher
    Nov 1, 2008
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      fierodeval wrote, On 01.11.2008 21:59 Uhr:
      > Yes, I understand. But when you speak about the "sqrt(2)", you are
      > speaking about the figure in the right of this image
      > http://www.devalvr.com/fiero/equicube.jpg . Te correct figure is in
      > the left and this figure is valid in the two directions.
      >
      > Then, if I understand correctly, you say that the figure for
      > equirect->cube conversion is the left image and for cube->equirect is
      > the right image?

      Yes. correct. Because the cube faces *could* contain more information in
      the corners.

      If the source was a equirectangular with 1/Pi as factor for the cube
      faces size then it is safe to just use the left type of conversion again
      because the pixels in corners are stretched by a factor of sqrt(2).

      If the source images are cube faces, for example of a rendering from a
      3D software, then you need to use the conversion on the right side to
      avoid losing resolution/information.

      The factor Pi*sqrt(2) would also be true if the equi->cube was executed
      with a factor smaller then 1/Pi*sqrt(2) to get the maximum out of the
      cube faces. Another case would be if you recover a equirectangular from
      a QTVR where you don't know the original resolution.

      --
      MfG,
      Thomas
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