A Sample Image

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dsjtecserv
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A Sample Image

Post by dsjtecserv » Sun May 23, 2010 11:31 pm

Here's a the result of my first shot at using Star Tracer on a previously-completed panorama. This is by no means approaching the images that Max has already demonstrated, but it shows what can be done with even relatively poor input. Read below for some things I learned.

Image

I still need to prepare the image better. The dashed trail left of center is because the trail overlapped the edge of the image, and thus wasn't as long as the others. I should have cloned it out before sending to Star Tracer. There are also various dotted trails from noise and other artifacts which don't necessarily show in this web-sized version.

Optimization needs to be done differently when the images a panorama. After some back and forth with Max it became apparent that you need to input a pretty-close horizontal FOV manually, and not optimize it. Also, don't optimize the b value (leave it at 0) but do optimize the vertical shift (e) in the Advanced options. For the first pass, optimize only Pitch and Rotation, then on a second pass add e. I don't know if that will work on all panos, but that's what worked for this one.

Upward replication of the sky close to the horizon was a problem, and it also tended to show a "shadow" of the alpha mask I was using. I solved that by outputting two images: each rotated ONLY in one direction or the other. I then layered them in Photoshop and used layer masks to include ONLY the "downward" rotation on each side.

Hope my learning experience helps others.

Dave

maxlyons
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Re: A Sample Image

Post by maxlyons » Mon May 24, 2010 7:40 pm

Dave,

Looks good!
Optimization needs to be done differently when the images a panorama...you need to input a pretty-close horizontal FOV manually, and not optimize it. Also, don't optimize the b value (leave it at 0) but do optimize the vertical shift (e) in the Advanced options. For the first pass, optimize only Pitch and Rotation, then on a second pass add e.
I think this is a very reasonable approach, but not necessarily mandatory.

Optimizing FOV is tricky, for boring math reasons aren't that interesting for most folks. The result is that the optimizer may end up settling on a "mathematically optimal" result that isn't what we want. In general, if you know the FOV it is best to enter it and not optimize it. If you don't know and have to optimize it, then inputting an initial value that is as close to correct as possible is a very good idea, and adding more star lines can help prevent the optimizer from producing bad results.

As for the vertical shift parameter, this is needed if the pano has been cropped after blending. In general, this is usually the case, so optimizing the vertical shift parameter is a good idea.

Lastly, incremental optimization in two passes can help prevent the optimizer from settling on an incorrect solution, which it may do on occasion for more math reasons that most folks probably don't care about! In future versions of Star Tracer I may add a feature similar to PTAssembler's "Auto-optimize" which does this incremental optimization (in multiple passes) automatically.

Max

Royal000
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Re: A Sample Image

Post by Royal000 » Tue Feb 03, 2015 5:22 am

Thanks...I'm pretty sure this is related to the way different systems use either the "," or the "." as the decimal separator. I'll investigate some more; if I send you a different version of Star Tracer, can you test it on your system?




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allanconner152
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Re: A Sample Image

Post by allanconner152 » Thu Oct 15, 2015 7:07 am

Yeah it's really appreciated work

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