Celestia Forums

Matthew Arcus wrote:Had a look at the inverse mapping problem, which turned out to be reasonably straightforward. I've put a little webpage with the results of
my investigations at:

http://www.users.globalnet.co.uk/~arcus/mmps/europa.html

There's also a new version of the code for download at (as before):

http://www.users.globalnet.co.uk/~arcus/mmps/mmps.tgz

The key addition is the -i flag, which tells "project" to generate the inverse mapping, which can be used with either the "perspective" or "rectilinear" (effectively, a perspective projection from infinitely far away) to generate a lat-long map from an image. rectilinear is easier, though will introduce distortion if perspective effects are significant.

The position of the planet can be set with the -lat and -long parameters (for the central point in the image) and there are some other parameters that define the orientation (-tilt and -turn, though I can't remember what
they do offhand, -tilt sounds like it ought to do the right sort of thing).

If you have a set of images of something from different directions do let me know and I will have a play - I couldn't find anything very suitable myself, but perhaps you know more about what is out there.

It would be nice to be able to fiddle with these things interactively, perhaps that's something I should look at - might need to get myself a faster PC for that though - I developed this stuff on a 133 MHz laptop and
my current box is a 400 MHz PII, so there's plenty of room for improvement there.

Next step I guess is joining up maps from multiple image sources, not something I know too much about (though I did work on a system for doing
this some time ago).

Had a bit more of a play with Celestia (another reason for getting a faster PC). Looks wonderful. How about deep sky objects - wouldn't it be fun to
fly through the Great Wall (or whatever it's called these days)?

Do let me know if this looks useful (or, of course, if anything is unclear or, god forbid, broken).

All the best,

Matthew.

t00fri wrote:Hi all,

this is to let you know that things seem to get moving as to generating cylindrical projection textures from space photographs.

Some of you will remember that I contacted Matthew Arcus two weeks ago and suggested to extend his projection software to the inverse task.

At that time, he was starting a vacation trip for two weeks. Now he is back and --amazingly-- already has finshed the job!

Matthew Arcus wrote:

t00fri wrote:Hi all,

this is to let you know that things seem to get moving as to generating cylindrical projection textures from space photographs.

Some of you will remember that I contacted Matthew Arcus two weeks ago and suggested to extend his projection software to the inverse task.

At that time, he was starting a vacation trip for two weeks. Now he is back and --amazingly-- already has finshed the job!

Glad to be of service. (It did only involve writing a small amount of new code though).

Matthew.

t00fri wrote:just to provide a flavor that my recent idea of converting brand new Cassini photos into Celestia textures via Matthews rectilinear projection code indeed works:

Below, you see how Phoebe looks meanwhile in my Celestia installation. I have used

-- Jens' color texture from the recent hires Cassini (RGB) photos of Phoebe
-- converted with Matthews projection software into a (partial) cylindrical texture that can be displayed in Celestia!

jim wrote:

t00fri wrote:just to provide a flavor that my recent idea of converting brand new Cassini photos into Celestia textures via Matthews rectilinear projection code indeed works:

Below, you see how Phoebe looks meanwhile in my Celestia installation. I have used

-- Jens' color texture from the recent hires Cassini (RGB) photos of Phoebe
-- converted with Matthews projection software into a (partial) cylindrical texture that can be displayed in Celestia!

Nice work with my ugly picture.
But I guess to build a more complete map of Phoebe is a bit to complex.
Now I hope NASA or ESA will release a Phoebe map once with a good 3D mesh.

Jens

Toti wrote:Fridger:

Perhaps you can try this idea:
You can build a cylindrical map with mmps and this image that Chris posted a few days ago:
http://photojournal.jpl.nasa.gov/jpeg/PIA06070.jpg
(Some Gimp/Photoshop work might be needed)

Toti wrote:Then you can create a displacement map by resampling the altitude ramp to a grayscale one. (The freeware Wilbur can do it)

Toti wrote:This map can be easily applied to an sphere mesh in order to obtain an acceptable 3D model of the satellite, with almost no "creative" licenses.

Toti wrote:I would do it myself, but for some reason, after a clean compile under Cygwin, mmps is doing curious things to the textures.

selden wrote:Toti,

What 3D design package are you using? Blender?
What function in it will apply a displacement map to the surface of a sphere?

Is the 3DS import/export library available for Blender again? The last time I tried to find it, the site where it was supposed to be had gone offline permanently, so I gave up.

selden wrote:Toti,

What 3D design package are you using? Blender?
What function in it will apply a displacement map to the surface of a sphere?

Is the 3DS import/export library available for Blender again? The last time I tried to find it, the site where it was supposed to be had gone offline permanently, so I gave up.

t00fri wrote:

selden wrote:Toti,

What 3D design package are you using? Blender?
What function in it will apply a displacement map to the surface of a sphere?

Is the 3DS import/export library available for Blender again? The last time I tried to find it, the site where it was supposed to be had gone offline permanently, so I gave up.

Selden,

there is a unified (download) site for all OS's

http://www.blender3d.org

Note the '3d' in that URL!

Look under Features and then Import/Export via Python scripts. Lots of 3D formats, including Studio Max.

Although you should clearly use the native Blender for Windows, rpm's under Cygwin are used like anywhere:

rpm -pql <name>.rpm

lists the content

rpm -pqi <name>.rpm
lists the 'boilerplate'

rpm -ihv <name>.rpm
installs
rpm -Uhv <name>.rpm
updates
rpm -e <name>
deletes an installed rpm
rpm -qi <name>
lists the boilerplate of an /installed/ rpm

etc.

Bye Fridger

Fridger wrote:That I am not sure whether I understood. Aren't you simply saying that you want to convert the artificial color map into a level gray map? That again would be easy and I can do it with Gimp.

Fridger wrote:Let me compile mmps with Cygwin. It's hard for me to imagine that this is not a trivial task...I get back to you soon.

Fridger wrote:I find their GUI confusing, but that's clearly my fault not theirs

Selden wrote:What 3D design package are you using? Blender?
What function in it will apply a displacement map to the surface of a sphere?

Is the 3DS import/export library available for Blender again? The last time I tried to find it, the site where it was supposed to be had gone offline permanently, so I gave up.

*) one displaces them at render time, ie. the mesh is not deformed when you work on it, but only when the final animation is done (this saves a lot of realtime resources. but it's not useful for our intent)
*) the other displaces a plane along universal z vector. Then you need to run a script that folds it into a sphere. I have done this several times in the past: it works
I will write detailed, step by step instructions.

Fridger wrote:Let me compile mmps with Cygwin. It's hard for me to imagine that this is not a trivial task...I get back to you soon.
It was absolutely trivial to compile:
after downloading and extracting,
cd mmps
make