More Punishment

Merry Christmas!!!

Google Earth now has entries for GigaPan. This is an amazing way to experience some places within Google Earth, but you’ll need v4.2 or later to see it.

In short, by placing a panoramic at the correct coordinates and specifying field of view, elevation, tilt, etc. it becomes possible to fly in to the image and look around it in detail. I decided to upload my night (hdr) panorama of Zurich but it wouldn’t let me — it wasn’t big enough! The image has to be at least 50 mega-pixels to be accepted. My original met this requirement but, as you may recall, I’d had to cut the image in 1/2 both horizontally and vertically in order to load it in to the HDR processing program. I could, of course, simply scale the image up but that would be cheating. So, I went back to the originals to try some new techniques.

There are two paths to follow… (1) Merge the images into an HDR with Photoshop and then do the tone-mapping with EasyHDR. Since I’d be loading just one 32-bit TIFF image, hopefully it would stay within EasyHDRs memory limitations. (2) Do HDR processing on each stack of images first and stitch those together into a panorama. This requires that the same transformation be applied to each stack in exactly the same manner or else there will be seams in the final image.

1) Merge into HDR with Photoshop

By restoring all the saved, aligned images I had made during my previous attempt, I had a good starting point. I recreated the three panoramas using PTGui and then loaded them all into Photoshop using “File::Automate::Merge to HDR”. The tone-mapping in Photoshop CS2 is poor compared to other alternatives, so at this point I saved it as a 32-bit TIFF.

Unfortunately, in the end I was unable to load even an image with 1/2 resolution in to EasyHDR. Windows programs that don’t do some sort of tiling of data (like Photoshop does) are generally limited to 2GB of memory. On to the next method…

2) Generate Multiple HDR Images and Stitch Them

The latest version of EasyHDR has some nice new features over what I used just 8 months ago. The trick here seemed to be to avoid anything that was dependent on the local image. To this end, I turned off the local mapping “mask” (which I don’t like anyway because it produces halos) and leave the general tone-mapping parameters at 1.0. I also never adjusted the black/white clip points, leaving them at the far ends of the spectrum. This would hopefully result in identical mapping for all image stacks and by saving in 16-bit mode there would be sufficient detail for me to adjust the total range in post-processing.

Before stitching, apply any filters that apply to a given image stack — noise-reduction, for example. Also, it’s likely that a lot of third-party software will not be able to handle gigapixel size images. You’ll have to run that processing on each part before stitching.

Other Things

Along with these changes, I switched the panorama generation to be “cylindrical” instead of “rectilinear” as Earth will do all the perspective alterations necessary. If you’re not familiar with the terms, the latter is the standard image that non-fisheye lenses will give you. It’s what the eye would see looking through a frame held in front of you. A cylindrical mapping, on the other hand, is what you would see if looked through a vertical slit held at arms length and then rotated your whole body, combining the all that is seen into a single image.

Here’s the final image… Click on it to browse it at full detail!  It should appear in Google Earth sometime in the future.  Look for it at 47.37593N, 8.54651E.

Zurich Night Panorama

1 comment to More Punishment

  • Irv Simpson

    Hey Brian,
    I’ve had this pop-up that keeps hitting me every two weeks saying “check Brian’s site”. Sometimes I send an email home and hope that I’ll check it out but, up until today I haven’t…

    So tonight, after everyone is in bed, I manage to search around and find a link by using a bunch of key words. . .and then I find that you haven’t added anything for almost a whole year! ;-)

    Hey, a funny story for you. . . You’ll remember that you gave Anne and I a pair of Google t-shirts. Now I’m not sure I should tell you this but Anne thought it didn’t look good on her, so she gave it to Jonathan. So he’s been wearing it a lot, especially at school. He wore it a few times when he was trying out for the senior soccer team and since the players were mostly older and didn’t know hi name, he now has a new nickname – Google!

    Kind of a weird name but better than many I could think of ;-)

    Anyhow, I’m hoping all is well with you and yours and that you had a good summer. I guess Christian must be in pre-school now so is France able to get around better with the little one?
    I also guess you’re keeping yourself busy? Let me know what’s a happening if you get the chance.

    Talk to you soon,

    Irv

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