3D shape, cartography, and geoid of Comet 67P C-G Options

[ngunn]

super simple comet model

Excellent! Now focus on the force vectors just at the points where they intersect the surface of the 'comet' and imagine them resolved into normal and tangential components. Chuck out the normal components and map the tangential ones as arrows drawn on the 'cometary' surface. You would then have a first approximation local slope direction map as requested by Mercure and charborob a few posts up. EDIT: now at post 227 in the other Rosetta thread, Early Orbital Operations.

EDIT: Interestingly, your diagram already shows that the steepest gradient (angle between force vector and the normal) is to be found on the inner side of the smaller lobe, exactly the place on the actual comet where there are features tentatively attributed to a landslip.

[Malmer]

no it is all mine
i used motion to make a "point cloud" from two videos

Ah, you used ESAs videos of their shapemodel and reverseengineered it. Clever.

I'm just using the "raw" images to build my own. (I want to make it from scratch just as an exercise in image processing)

I'm using a very simple shape from shading algorithm that i made myself to add the details. (Would make your skin crawl)

The race is on

[Y Bar Ranch]

I'd be interested in grabbing whatever you guys come up with. Point cloud is OK. Then I can play with gravity modeling.

[Malmer]

Will post as soon as it is resonably correct.

[JohnVV]

I'd be interested in grabbing whatever you guys come up with. Point cloud is OK. Then I can play with gravity modeling.

i just zipped up a the mash as of today
-- a low res 1.3 meg .obj file
the zip contains a map-grid uv mapped
https://googledrive.com/host/0B6ZYAd08tZL-V....09.03.2014.zip

[Malmer]

i just zipped up a the mash as of today
-- a low res 1.3 meg .obj file
the zip contains a map-grid uv mapped
https://googledrive.com/host/0B6ZYAd08tZL-V....09.03.2014.zip

I will use it to line up mine so that we work in the same coordinate system.

(Just noticed that I made my 100th post and became a "Member" today after nine years. I guess I read a lot and post very little...)

[Gerald]

OK, here's my super simple comet model...

Does the model already contain the shift due to rotation?

[Mercure]

map the tangential ones as arrows drawn on the 'cometary' surface.

Yes, I also think that would be the best visualisation, with arrow length indicating gravitational pull. Or perhaps visualize it as 'stubs' or 'sticks' on the surface of the model, with tilt and length of the stubs indicating gravitational direction and pull.

Such a visualization would also be interesting seen in conjunction with outgassing, to see if hotspots correlate with areas of relatively weak gravity or not.

Y Bar Ranch, very interesting first stab at a visualisation, thank you for doing it.

[MarsInMyLifetime]

Another way that readers might better associate with the upcoming Philae landing process would be to have a set of points positioned above each candidate landing site about 10km off the surface with a downward pointing arrow representing the direction and relative strength of attraction on each such 100kilogram point. Then we could appreciate the unique issues with being positioned correctly at release for a descent into the intended spot. Ignoring the orbital velocity, just the "down" vector at those locations would be interesting to see. Is this possible, and even useful for others?

[Y Bar Ranch]

Does the model already contain the shift due to rotation?

No...just a simple malformed dumbbell right now

[CAP-Team]

i just zipped up a the mash as of today
-- a low res 1.3 meg .obj file
the zip contains a map-grid uv mapped
https://googledrive.com/host/0B6ZYAd08tZL-V....09.03.2014.zip

Thanks! Let's see if I can convert it to 3ds and then to CMOD

[mcgyver]

Thanks! Let's see if I can convert it to 3ds and then to CMOD

What about STL? Is it possible?

[JohnVV]

3ds to cmod is rather easy
now the plugin is for the OLD!!! blender python API
so you need to use Blender 2.49b

and building the tool " cmodview" from the celestia SVN source will save a ASCII mesh to a binary mesh

also my mesh IS NOT a "3ds "
it is a Alias Wavefront format
that is almost identical to the PDS vertex shape file

[Malmer]

3ds to cmod is rather easy
now the plugin is for the OLD!!! blender python API
so you need to use Blender 2.49b

and building the tool " cmodview" from the celestia SVN source will save a ASCII mesh to a binary mesh

also my mesh IS NOT a "3ds "
it is a Alias Wavefront format
that is almost identical to the PDS vertex shape file

The 3ds format is really not much fun. The 3DS format does not support more than one UV coordinate per vertex. You will get problems along UV seams

[djellison]

What about STL? Is it possible?

Download and install Blender ( http://www.blender.org/ )

Import OBJ

Export STL.

Done.

(Caution - you will not want to try and print an object like this on a 3D printer as-is. You will need to bifurcate it into hemispheres - such as I've done for other small bodies like Eros, Itokawa and Vesta http://nasa3d.arc.nasa.gov/search/ellison/model )