# Central spherical projection of vertically cropped image

(ChameleonScales) #22

What I meant when I said:

is that you can get the same result on a 1 by 1 sphere with different projections, as this video shows:

Here is the file of the video:
Axial vs central.blend (1.1 MB)

yet, it’s important to distinguish the central and axial projections since they behave very differently when you apply other transformations on top of it, that’s why I think we have to use the words central or axial for describing how the vectors are oriented and where they start from and spherical or cylindrical to describe what type of solid the vectors collide with. It’s the exact same terminology as used for central cylindrical and I don’t know why we shouldn’t expand it.

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(Secrop) #23

If you scale the original coordinate system, you need to take that scaling in account prior to the projection calculations… ‘Axial’ in this situation in no more than a non uniform coordinate system.
As the equations are mainly trignometric entities, you’ll get wrong projections if you use anything other than the unit sphere (which is the case if you scale your sphere). That’s why you allways have to divide the coordinates of the sphere by it’s radius before making anything else (as that wikipedia page clearly shows).

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(ChameleonScales) #24

Sure, anyways. I must say you helped me a great deal for my bigger problem. However, it’s getting more complicated than I thought so I just posted a new question, this time explaining the whole thing:

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(ChameleonScales) #25

as I posted there I figured it out. I will prepare a nice file to use as a tool to straighten cylindrical panoramas and upload it there.

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