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LROC news and images
John Moore
post Nov 6 2017, 08:06 PM
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Thanks, Seán...lunar animations are well overdue...it's all Mars at the moment (no offence intended to your Mars's animations that are superb).

John Moore
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Phil Stooke
post Nov 7 2017, 12:45 AM
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Yes, Sean, your animations are great!

Returning to the Permanently Shadowed Region atlas I mentioned a few posts earlier, here's an example of how the data can be used. This image has 4 sections. At top left is the Shoemaker PSR, enlarged and cleaned of artifacts, especially the stripiness in the original LRO mosaics. At top right is a mosaic of LRO Mini-RF radar images registered to the LROC image. At lower left is a composite of the two (not made by merging them, though that would be possible as well). Rather, the brighter pixels in the Mini-RF image were selected, and that selection (that pattern of pixels) was applied to the LROC image and brightened. It's not necessary to do it, I was just experimenting. Finally, at lower right the Lunar Prospector impact site is indicated - not guaranteed to be exact, but this is probably the best image we have of that location. A LOLA shaded relief image could be made as well, but that will have to wait.

North is at the top.

Phil

Attached Image


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... because the Solar System ain't gonna map itself.
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Sean
post Nov 7 2017, 02:52 AM
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Ah thank you.

I wonder Phil if you know where I can get my mitts on an LROC global mosaic with no shadows? It exists as a layer in the wonderful Quickmap LRO model online and can't seem to find it in the usual places.


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Sean
post Nov 7 2017, 03:29 AM
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Lunar Orbit 2, made with LROC data



4k60 version over on Youtube


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Sean
post Nov 9 2017, 12:00 AM
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Maria, made with LROC data...



4k 60fps version over on Youtube




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scalbers
post Nov 9 2017, 12:59 AM
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Pretty nice to see these Sean - this reminds me of the Kaguya videos and such. I wonder if you are using (or have considered) a BRDF (bidirectional reflectance distribution function) with the lunar surface. For example this would show things like the opposition effect and other differences in brightness with the geometry, over and above the shaded relief. I've been using a BRDF in my Earth view simulations and finding or formulating one for the moon might be of interest.


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Sean
post Nov 9 2017, 01:32 AM
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Ah thanks but I wouldn't know where to begin with BRDF! I'm really just trying to present the data in an easily digestible format to the highest quality I can muster, along with some subtle image processing.

Is there a primer you can recommend? How would I utilize it with this dataset?


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scalbers
post Nov 10 2017, 07:46 PM
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It's possible others on the forum have considered this in lunar rendering. To start I can suggest this as one reference on Hapke parameters. Another more recent reference is here.

In brief, I assume your images use terrain slope and solar illumination geometry to get the brightness at any location. The BRDF (or ARF for anisotropic reflectance factor) is simply a correction factor to multiply the brightness by that depends on some additional aspects of the geometry. One key quantity would be the phase angle, among some others. There would be a tradeoff with these functions in terms of simplicity and accuracy.


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Sean
post Nov 10 2017, 08:55 PM
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Hills, made with LROC data



4k60 version over on Youtube


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Sean
post Nov 10 2017, 11:21 PM
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I made the videos with data already assembled into global mosaics, each set well over 100k pixels across. I optimized these to get them to fit into my 32gb PC as well as polygon culling at rendertime which dramatically increased efficiency. Each frame takes about 12 seconds on average at 4k resolution. Each video has around 1600 rendered frames which I then interpolate to reach a more comfortable orbit speed.

QUOTE (scalbers @ Nov 10 2017, 07:46 PM) *
It's possible others on the forum have considered this in lunar rendering. To start I can suggest this as one reference on Hapke parameters. Another more recent reference is here.

In brief, I assume your images use terrain slope and solar illumination geometry to get the brightness at any location. The BRDF (or ARF for anisotropic reflectance factor) is simply a correction factor to multiply the brightness by that depends on some additional aspects of the geometry. One key quantity would be the phase angle, among some others. There would be a tradeoff with these functions in terms of simplicity and accuracy.



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scalbers
post Nov 10 2017, 11:51 PM
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Sean - sounds like you have a well oiled processing pipeline, so I want to avoid throwing too much of a monkey wrench in it smile.gif At least at an academic level, here's some further insight into what could be possible in this Celestia Matters forum thread. I'm still learning about the Hapke parameters, though I am familiar with the subset of them that use the Henyey-Greenstein functions (that key off of the phase angle) so I should know how to code that part.


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mcaplinger
post Nov 11 2017, 01:45 AM
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QUOTE (scalbers @ Nov 10 2017, 11:46 AM) *
In brief, I assume your images use terrain slope and solar illumination geometry to get the brightness at any location.

Isn't this image data draped over the DTM? If it wasn't, there wouldn't be any albedo features. Since it is, the BRDF is baked into the image at least for the original imaging geometry.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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Sean
post Nov 11 2017, 04:01 AM
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No worries Steve, I understood some of the words you used! wink.gif

As MC said, this is imagery draped over DTM, as straightforward as it gets from a rendering standpoint.

Steve, if you were referring to my request earlier regarding the no shadow mosaic found on the LROC quickmap?...if there is a way to achieve that with your recommended method that isn't too taxing for my blue collar brain then I'll check out your suggestions. Appreciate the assist.


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scalbers
post Nov 11 2017, 02:34 PM
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Thanks for the reminder about your "no shadows" post. I notice online these datasets for Hapke Normalized and Empirically Normalized mosaics: http://ode.rsl.wustl.edu/mars/pagehelp/qui...lroc_mdremp.htm

Hopefully these have the corrected albedo in them (with no shadows), so then in theory one could apply the BRDF for various viewing geometries.


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Sean
post Nov 14 2017, 07:54 PM
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'Moon' is a montage of previous videos set to 'Lux Aeterna' by György Ligeti



Full 6 minute 4k60 version over on Youtube





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