Hiding the Tripod in a Sphere

Hiding the Tripod
in a Sphere

by Ronny D'Hoore
Copyright © 2000 ProxyVista AB

This is part of a series of documents that provide additional information on
the freeware Panorama Tools by professor Helmut Dersch.

Everyone who has made "fully immersive" (360 x 180 degree) panorama spheres knows the problem: when you pan down in the viewer, you see the tripod.

When panning down,
you see the tripod

There are at least two ways to do something about this. The first is to manually edit the image in a graphics editing program. Adobe PhotoShop's rubber stamp tool is great for this purpose. But it requires quite some effort to do to nicely, and not all backgrounds lend themselves to editing.

Another solution is to insert a logo, or sometimes called a tripod cap. You simply paste your logo (in a circular form) over the very bottom of the spherical panorama. This method is more suitable if you need to produce many panoramas.

Editing the tripod away

Pasting a logo on top

Now, in both cases, you need to somehow get the floor frame into PhotoShop (or whichever graphics program you use). PhotoVista (Live Picture's first class stitching program) actually provides a way to export the viewing window to a BMP (Windows bitmap) file, and later import the edited version again. However:

Mac or Linux users cannot use PhotoVista
not every Windozer has PhotoVista
PhotoVista 1.3.2 has a bug which does not import the frame 100% in the same perspective. So even if you had no stitching errors before, you may end up with one after importing an exported frame. Sometimes it also does something weird to the colors.

So, we'd better use Helmut's tools. In his Frequently Asked Questions, Helmut gives a hint towards the solution:

3.3. How to edit the zenith in a Spherical Panorama?

This is the most difficult part of a spherical panorama, and can not be edited in the original 'PSphere' mapping (you can try, but it probably will not fit very well). Solution: Take the upper half of your spherical panorama, and convert to fisheye format using the 'Remap' tool:
from: PSphere
to: Fisheye Vertical
HFOV: 360
VFOV: 0 (ignored).

The 'pole' is now in the center of your image, and can be easily edited. Later, convert back using either the opposite transformation (Note, that HFOV of the fisheye image is only 180 degrees!), or use the 'Adjust' tool with 'yaw' set to 90 degrees. Insert the transformed piece into your original image.

However, we don't want to edit the zenith, we want to edit the nadir. Now, you may try to do the opposite of what he describes, and take the lower half of your spherical panorama, and convert it to Fisheye Vertical format, but you won't get anywhere that way.

The trick is to first rotate your image 180 degrees. Then the same steps apply. Then at the end, simply rotate it one more time.

So, hackers know enough now, but for the others, here comes a detailed explanation of exactly what to do to insert a logo, with plenty of pictures. I'm using PhotoShop and Windows. If you use something else, you should not be having much trouble to convert my procedure for your platform, as long as you have the Panorama Tools plug-in installed in a suitable graphic program.

If you want to edit away the tripod instead of using a logo, the process is quite the same, except that you start at step 5, and in step 11 you edit the image instead of pasting the logo.

Open your logo in PhotoShop (File > Open). It should be about 260 x 260 pixels big, and be either a PhotoShop file (.PSD) with the corners around the logo made transparent, or a GIF file with transparent corners. An example:

Select the whole image (Ctrl-A) and copy it to the clipboard (Ctrl-C). Close the file.

Open your panorama (PSphere). Your tripod will be smeared along the bottom.

Do "Image > Image Size" and write down the width of the panorama. You will need it later. Click Cancel to get rid of the Image Size box.

Rotate the image 180 degrees (Image > Rotate Canvas > 180°). Now your tripod hangs on top.

Remove the bottom half of the image: Image > Canvas Size. For "Height", type 50 and select "Percent". For Anchor, select the top middle tile. Click OK. You end up with the top half:

Remap it to a vertical fisheye image: Filter > Panorama Tools > Remap.

Convert from:

PSphere

HFOV:

360

VFOV:

0

Convert to:

Fisheye Vert.

In "Prefs" (click the button), you should have option (a) disabled (because the image size will be completely different, and filter plug-ins have no means to change the image dimensions), and (b) enabled. The converted image will be saved with the file name which you write there at (b).

You will also see the result (or at least a slice of it) in Photoshop. But we don't need that one. So, undo the last two steps (which is done in the history window), so that you recover the full (rotated) panorama as in step 4.

Now open the result of the remap operation (File > Open).(The file name you provided will have gotten a number appended.) The result is a cute top view of your tripod!

Now paste your logo in the center of the image (Ctrl-V). Merge the new layer in the background picture (Layer > Merge Down).

Next, convert it back to PSphere: Filter > Panorama Tools > Remap.

Convert from:

Fisheye Vert.

HFOV:

180

VFOV:

0

Convert to:

PSphere

Close the useless file (without saving) and open the actual result. ( Take the file name with the next number.) So now your logo is smeared on the top, instead of your tripod. However, the image size has changed, so we have to resize this image to match our original image. So do "Image > Image Size", make sure "Constrain Proportions" is enabled, and either correct the width (use the width of the original panorama in pixels), or type 63.68 percent. Don't worry about image degradation. The logo, although eventually just a small thing sitting on the floor, occupies a lot of space compared to the rest of the panorama, and will be crystal clear.

Now, in order not to degrade the quality of our original panorama, we will paste as little of this new image (which has been transformed thrice, and is thus of inferior quality) as really necessary. That means, only the part with the logo. Therefore, we will remove the bottom part and keep only the part where the logo is. Do "Image > Canvas Size", and type 33 percent. For Anchor, again select the middle top tile.(If your logo was bigger than I expected, do "Edit > Undo" and try it again with a bigger percentage.)

Hint: if (unlike me) you are not using any shadow on your logo, you can even crop your image more precisely so that only the logo is there, and save it in a file, so that if you later want to insert the logo in future panoramas, you can skip all the previous steps .

Select the whole image (Ctrl-A) and copy it to the clipboard. Then close the image without saving.

Now paste it in the original panorama (Ctrl-V). It will end up in the middle:

To get it to the top quickly and neatly, use the following trick: select the whole image (Ctrl-A) and do Layer > Align to Selection > Top. The logo will move to the top left corner of the image. Then remove the selection (click anywhere in the image with the marquee tool), and flatten the image (Layer > Merge Down).

Finally, rotate the image back (Image > Rotate Canvas > 180°) and save it.

You're done! When you load the image in a viewer, and pan down, the logo will smile at you.

Note: Another (quick-and-dirty) method to generate a tripod cap in a panorama is to simply put a colored band in the bottom of your image and add your title/copyright at the top of the band in wide lettering. It won't look fancy, but it's fast!