focal length for Dodecahedron (12 images)?

[Jan Martin]

Hello

I need to shoot a 360x180 pano as a Dodecahedron (12 images).

What is the ideal focal length?
With what roll, pitch yaw values to shoot for as little overlap as possible?

What kind of tools do you recommend to do this kind of planning?

Thanks,
Jan

[Bruno Postle]

I would make up twelve blank images, each a different colour, and load
them into Hugin. Then I would drag them around the preview and adjust
the focal length until I was happy with the arrangement and overlap.

Until you see them in the preview you don't know whether you want
portrait or landscape, maybe even rolling the lens would give better
coverage.

--
Bruno

[Wirz]

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Hi Jan,

Based on what wikipedia says about regular dodecahedra and pentagons and
after some scribling:
Seen from the centre of a regular dodecahedron the height of one of the
faces has an angle of 1.24 or 70.8 degrees. The diagonal of a pentagon
face has an angle of 1.31 or 74.8 degrees.

If I assume, that you want to shoot one photo down, one up and five on
an upper and a lower circle each, then you'd have to shoot landscapes to
get the benefit of 70.8 degrees, for portraits it's the 74.8.

I hope I'm not missing any perspective related complication.

cheers, lukas

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Do not believe the naysayers who say it cannot be done.
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[Wirz]

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Hi Jan,

for completeness: On a full format sensor 70.81 deg (vertically) should
be f=16.9mm.

The lower 5 pictures should be down 21.22 deg, the other 5 up 21.22 deg.
Horizontally they should be spaced at 72 deg in each level. All these
10 pictured would be landscape. If you do portrait you'd need f=15.7mm
or less.
The single down facing pic needs to be parallel to one of the pics in
the lower ring. The analogue holds for the up facing photo.

(All of that is untested.)

cheers, lukas

On 09/10/15 23:23, Wirz wrote:
> Hi Jan,
>
> Based on what wikipedia says about regular dodecahedra and pentagons and
> after some scribling:
> Seen from the centre of a regular dodecahedron the height of one of the
> faces has an angle of 1.24 or 70.8 degrees. The diagonal of a pentagon
> face has an angle of 1.31 or 74.8 degrees.
>
> If I assume, that you want to shoot one photo down, one up and five on
> an upper and a lower circle each, then you'd have to shoot landscapes to
> get the benefit of 70.8 degrees, for portraits it's the 74.8.
>
> I hope I'm not missing any perspective related complication.
>
> cheers, lukas
>
>
> On 09/10/15 21:37, Jan Martin wrote:
>> Hello
>
>> I need to shoot a 360x180 pano as a Dodecahedron (12 images).
>
>> What is the ideal focal length?
>> With what roll, pitch yaw values to shoot for as little overlap as possible?
>
>> What kind of tools do you recommend to do this kind of planning?
>
>> Thanks,
>> Jan
>
>
>
>

- --
Do not believe the naysayers who say it cannot be done.
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[dkloi]

With a bit of trial and error, you can get away with a HFoV=66deg on a 3:2 aspect ratio sensor (in portrait), i.e. just over 18mm focal length on a 36mm x 24mm sensor (see attached). I've rotated the Nadir and Zenith shots by 90deg.