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Old 10-31-2018, 09:41 PM   #1
martins
Orbiter Founder
Default New Hyperion textures

And here is the next body to get a makeover: Saturn's moon Hyperion. This one was quite a challenge. Hyperion is an irregularly shaped "potato" of a rock, a fact that, erm, hasn't been very well represented in the current default Orbiter installation . I found some low-res shape models, but no good texture maps except a very coarse one by Phil Stooke that seems to pre-date the Cassini data (and was used for the current Orbiter 2016 release version).

So I decided to generate my own texture map by projecting the available raw Cassini images onto the shape model. The problem here was that the camera position in the model frame wasn't known, so I had to infer the position by rotating the model and mapping its silhouette onto the image. For the iconic front view that went fairly well, but some of the other views required a bit of imagination, not least because the shape model is less than perfect. Also, some areas are not covered at all. Instead of leaving them blank, I used some artistic license and mapped random image bits into them.

The colour balance was adjusted to roughly correspond to some images I found claiming to be "true colour".

The textures are fairly low-res, so I didn't bother putting them on the high-res texture archive. They will be inserted directly in a future release package. If you want to try them, I've attached them to this post. Note that this also contains a replacement Config\Hyperion.cfg to refer to the new textures.

Please be aware that this update only addresses the moon's appearance, not its orbital and spin characteristics. Hyperion's orbit is severely perturbed by Titan, and its spin goes through chaotic phases, so modelling those will be an entirely different challenge. Be my guest!

Let me know of any issues.

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File Type: zip Hyperion.zip (1.32 MB, 14 views)
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Old 10-31-2018, 10:28 PM   #2
GLS
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What a nice break from SSU.
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hyperionsaturn.jpg  
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Old 10-31-2018, 10:48 PM   #3
Marijn
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Looks great!

Quote:
Originally Posted by martins View Post
 Hyperion is an irregularly shaped "potato" of a rock, a fact that, erm, hasn't been very well represented in the current default Orbiter installation .
Are you saying it's possible that a future Orbiter version might offer functionality to deal with these irregular shapes?

I am asking this because, at the moment, I am working on an add-on which, in short, allows a user to to select an asteroid from the JPL small body database, select a flight plan from the Nasa trajectory browser for it and download this as a ready-to-fly scenario with everything set up. There are currently over 600.000 asteroids in the database.

So over the last few days, I've been thinking about the question whether it would be possible to automatically generate the meshes for an asteroid based on a handful of parameters like estimated diameter, absolute magnitude, class etc.
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Old 10-31-2018, 11:06 PM   #4
martins
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I'm not sure what you are asking. If all you know about the shape is the mean diameter, then the best you can generate is a sphere. You need a bit more information to produce an irregular shape, such as the coefficients of a spherical harmonics expansion. If you have multiple images of overlapping surface regions, you may be able to infer a shape model using photogrammetry techniques, but that isn't trivial. It requires identification of landmarks or corresponding surface patches, then optimise the shape model to fit all the images.
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Old 10-31-2018, 11:33 PM   #5
Marijn
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Quote:
Originally Posted by martins View Post
 I'm not sure what you are asking.
Sorry for being unclear. I misread what your wrote because I wasn't aware that Hyperion was implemented as a sphere. I thought you were hinting on something new to deal with irregular shapes in general to make these things less of a challenge.
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Old 11-01-2018, 02:57 AM   #6
boogabooga
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Hi Marjin, you might be interested in this:
MPC Database Asteroid Viewer and Exporter v2.0.3
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Old 11-01-2018, 08:01 AM   #7
Marijn
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Quote:
Originally Posted by boogabooga View Post
 Hi Marjin, you might be interested in this:
MPC Database Asteroid Viewer and Exporter v2.0.3
Thanks for the suggestion! I'll have a look.
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