# How do I remove PTGUI's black top/down circles on a QTVR / CUBIC?

I'd like to know how to remove PTGUI's black circle holes when converting an already flat 360 pano to an Equirectangular QTVR / Cubic.

I do understand that the Top & Down generated images have those holes since they are curved to fit the dimensions, yet I still thought to ask here since I already have 6 cubic faces and there is no black hole in their top down and I have no idea how to do that in PTGUI.

• Can you elaborate on what you mean by "I already have 6 cubic faces..."? Do you mean you are trying to turn 6 cube faces into an equirectangular? Because your first paragraph makes it sound like you're starting with a cylindrical 360 pano. What is the input you're feeding into PTGui? Can you post it as an image? – inkista May 12 '16 at 15:40
• Hey inkista, the 6 cubic faces are generated by the cubic VR tool. The original image is a 2.5:1 pano – erezT May 12 '16 at 15:45

You have to cover the top and bottom of the sphere in your panorama.

With this specific panorama, you can't do anything about the black voids, because you started with a 2.5:1 360 cylindrical panorama. So you're missing the top and bottom of the sphere, which it's filling in with black.

To make an equirectangular (and cube faces/QTVR Cubic) you need to cover the zenith (straight up) and nadir (straight down) views when you shoot and include those images in the pano stitch.

This is why panorama heads rotate both in yaw (around) and pitch (up-and-down).

An equirectangular is not just a 2:1 rectangle, it's depicting an entire sphere. The equirectangular projection represents a sphere by turning the longitude/latitude coordinates into Cartesian x/y coordinates. Cylindrical panos, by their very nature, never cover the zenith/nadir views.

See also: How are virtual tour photos taken?

• This is one of the most amazing answers I got here inkista, so detailed thanks man. So just to be clear here, a 20mm wide angle lens taken at 6 faces would do the trick I guess, what would be the name of this kind of photo if I'd want to search google? Is there any library of photos that you can link to? Thanks again, Erez. – erezT May 12 '16 at 17:04
• @erezT You may want to ask as separate questions for more detailed answers. 20mm won't work the way you say. You can only get away with 6 shots if you're using a fisheye lens, and you may still need 8. Think more like 20-30 shots in multiple rows. Search on "equirectangular" or "photosphere". And panoramas.dk is one place to start. Unfortunately the two best resources I knew are gone; Eric Rougier's From Paris site is under construction, and the Panoguides board got eaten by spam. – inkista May 12 '16 at 17:26
• @erezT I repeat: see the How are virtual tour photos taken? Q&A. – inkista May 12 '16 at 17:26
• Re the link, I read it and the answer there was 6shots of 20mm wide angle, maybe I read the wrong answer? – erezT May 12 '16 at 18:00
• @erezT. PLEASE ask this as a separate question. There's not enough room here in comments to answer this question properly, and it hides it from future Googlers who have the same question. And I'd suggest going through my answer as well as Matt's. Mine was added 3 years later, so the chances of it being accepted were always low. :) – inkista May 12 '16 at 18:15

It's actually a reasonable question, and my guess is, the majority of people who deal with equirectangular panoramas run into this problem sooner or later.

If you are still facing this issue, I've written a free panorama editor that can patch the nadir and zenith points:

https://dizzylogic.com/panotwist

It's geared specifically towards equirectangular panoramas (360° x 180°). With PanoTwist, you can patch nadir/zenith with a uniform color (either specific color, or the average color under the patch) or with an image of your own choosing. You could, for example, use your company's logo as a patch.