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spinning globe

Aug 4, 2011, 01:13
Post: #1
spinning globe
Hello,
I've created a spinning globe through the filters/animation/spinning globe function. It works just fine but the function doesn't complete the globe. There is a slender seam that runs from the north pole to the south pole. Is there anyway to close that seam so that the globe is a perfect globe?
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Aug 4, 2011, 07:05
Post: #2
RE: spinning globe
Didn't you ask already this question there: http://gimpforums.com/thread-spinning-globe

And if the answer didn't help, why so Smile

(posting the original picture and maybe the final globe may also help us understand your problem).

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Aug 4, 2011, 10:26
Post: #3
RE: spinning globe
that answer didn't help because i don't know what you're talking about.
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Aug 4, 2011, 13:24
Post: #4
RE: spinning globe
I'm only talking about some simple Gimp actions... If you need the whole procedure in slow motion, I can do that too, it you tell me which move(s) I should slow down.

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Aug 5, 2011, 16:55
Post: #5
RE: spinning globe
ofnuts, have you created a spinning globe, and if you have do you know of the seam that i am writing about? i have zero experience with gimp. i found out, through accident, that i could create a spinning globe in gimp to complete a class assignment. it works perfectly except for that seam. i went to youtube and downloaded a video that explains how to create the spinning globe in gimp. it is very easy to follow that video. i guess in order to make the globe completely whole without the seam i would need detailed instructions to accomplish the task. maybe you could make a video of this procedure that you know of and post it to youtube.
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Aug 5, 2011, 17:46 (This post was last modified: Aug 5, 2011 17:49 by ofnuts.)
Post: #6
RE: spinning globe
Yes, I tried... what happens is this:

If you make a spinning globe with this:
[attachment=589]

Each frame of the spinning globe is obtained by joining the image to its copy, and taking a square from it:

[attachment=590]

So if the left and right side of your image do not join properly, as above you get a seam in the spinning globe, while if you use an image that can be joined seamlessly to itself:

[attachment=591]

Then there won't be any seam in the globe:

[attachment=592]

More on creating a seamless image later.

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Aug 5, 2011, 18:21
Post: #7
RE: spinning globe
Hello ofnuts, this is the image that i used to create the globe. it's a nasa photo so there isn't a copyright infringement. work with it if you will.

image: http://www.nasa.gov/images/content/13570...iew_lg.jpg
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Aug 5, 2011, 19:04 (This post was last modified: Aug 5, 2011 19:04 by ofnuts.)
Post: #8
RE: spinning globe
A simple way to create seamless image is to apply Filter/Map/make seamless. However, this makes the image seamless left-right, which is nice, but also top-down which is uncalled for. And the algorithm is a bit brutal. So, if we want to do it ourselves:

1) we start with an image which is a bit wider:
[attachment=593]

2) we split it in two half images, and swap them
[attachment=594]
Note that by construction, the left and right edges of that image match perfectly.

3) we overlap the half-images in the middle, and blend them together
[attachment=595]
The image used here is a worst-case, and even then the spinning globe produced isn't so bad.

More later on a real image, I have to dig my archives.

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Aug 5, 2011, 20:57 (This post was last modified: Aug 5, 2011 20:59 by ofnuts.)
Post: #9
RE: spinning globe
Okay, lets try so real work:

Let's say you have a picture of this world-famous museum (this picture is already improved from the original, the perspective has been corrected so that all horizontals are truly horizontal).
[attachment=596]

To make it more usable in a spinning globe, we add some space at top and bottom:
[attachment=597]

If that picture is cut in an arbitrary square for a spinning globe, the seam is quite sensible:
[attachment=598]

So let's try the recommended method. Split and swap:
[attachment=599]

Then we find a nice overlap. It happens that the circle window is almost where we want an overlap on both sides. So we use that, plus a gradient in the transparency channel for a smooth blend:
[attachment=600]
You'll notice that the outer edges of this image do match:
[attachment=601]

However, there is a small catch, the final image isn't square, we are missing 30 pixels. But this is is well within the limits of an acceptable horizontal stretch:
[attachment=602]

(To avoid overloading GimpForums (and the navigator of the unsuspecting reader) I don't publish the animated images here, but one only has to run the spinning globe script on the fixed images posted)

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Aug 5, 2011, 21:38
Post: #10
RE: spinning globe
(Aug 5, 2011 18:21)rascaal Wrote:  Hello ofnuts, this is the image that i used to create the globe. it's a nasa photo so there isn't a copyright infringement. work with it if you will.

image: http://www.nasa.gov/images/content/13570...iew_lg.jpg
Two problems with this photo:

1) there is a very slight seam (ie, left and right border aren't a perfect join). But it' s hardly noticeable on a spinning globe. See if you can see it in the still frame...

2) if you create a globe from the full-size picture, you can have optical effects created by the interference between the frame rate of the animation and the display refresh rate. One such effect looks like an horizontal seam going from top to bottom. Gimp isn't a video application, it's not optimized for animated images. Again, look at the still frames generated and see if the defect is there. If so, tell me:

- at what size was the picture from hwich you generate the globe
- how many frames you specified
- how many colors you specified

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