Realigning John van Vliet's Mercury texture: how?

[StarSeeker]

I am using http://www.celestiamotherlode.net/creat ... ercury.zip which is the first 8K Mercury map from John van Vliet. Unfortunately, the Locations in Celestia do not properly line up with the texture, or vice-versa. (I noticed the Hun Kal crater at -21.4 longitude while it is by definition at -20, but no matter; I'm sure it's easier to nudge the terrain.) How would I go about realigning this texture to match up with the Locations?

I need to know two things: how do I move textures in general, and how far would I have to move this texture, if you know offhand? The latter I can T&E if necessary.

[StarSeeker]

*bump*

Surely someone has run into texture moving before.

[selden]

You have two options:

1. Use your favorite image editor to shift the contents of the image left or right so it wraps around on the other side.

In a recent posting on the Development forum, Fridger mentioned that Gimp can rotate textures if you enable the "Wrap" option.

See http://www.celestiaproject.net/forum/viewtopic ... 2996&72996
and the subsequent postings in that thread.

2. Modify the RotationOffset value in Celestia.

[edit]
or you might try to contact John directly and ask him to repair the texture image.
[/edit]

[John Van Vliet]

so it is 1.4 deg off . i will look into it
the base image is this one --an OLD map
http://astrogeology.usgs.gov/SolarSyste ... e_cyl.tiff

[StarSeeker]

Well, like I said I'm not really sure if it's the texture or the location database. But it's off.

RotationOffset? I presume that's in solarsys.ssc?

Thank you John; I'll wait for further posting from you before I try fixing anything myself. The texture is pretty sweet and I'd rather not break it with my newbie hack-and-slash.

[Chuft-Captain]

2. Modify the RotationOffset value in Celestia.

Correct me if I'm wrong, but I believe that using this second technique (although fine to achieve the alignment of the texture) actually changes the planet's orientation with the sky (in terms of longitudes), so for example a satellite/spacecraft etc. in orbit having the planet as their frame of reference would for example travel over the longitude 180 degrees at a certain time according to published data, but the texture at that longitude would be for perhaps the 181.4 degree longitude, so it would appear that the spacecraft was in the wrong position.

(Of course, even if I'm right, this is not an issue if you're not worried about absolute accuracy -- if so, use the first technique)

[selden]

CC,

Changing the RotationOffset does change the orientation of the body. For a spherical body this just changes the apparent location of its prime meridian -- in this case it shifts the map of Venus slightly in an east-west direction. If only the one map is being used, then this might be a reasonable workaround. If different maps are being used, however, it's no good, since they'd each have a different offset.

[StarSeeker]

I changed the RotationOffset. This does not work: it rotates the whole planet, texture included.

So the terrain will need to be repositioned. Might I recommend using the Ibsen and Petrarch Craters and Arecibo Vallis, a rather obvious set of close features in the Caloris Antipode region, as a reference?

[John Van Vliet]

well i wont be able to recheck the map because i dont have acess to the box where they are stored , for the next 6 mo.
But as far as i know the longitude should be correct ???
but then again who knows

[StarSeeker]

I am not sure; I suspect your terrain is actually correct but the landmarks in Celestia are wrong for whatever reason.

[John Van Vliet]

could be, with so many people doing diferent things an error is bound to crop up now and then .

[StarSeeker]

Do you wish to adjust this yourself or have me do so and upload a copy to CML?

[John Van Vliet]

you will nead to make the adjustment and upload it to cml
at this time my os is a harddrive with no place to run it .

[StarSeeker]

Okay, I made the adjustments, and attempted to upload it, however, it timed out and then took me to the main page again. In the meantime, I am hosting it on my site: http://www.sunandshadows.com/common/8kMercury.png . Sorry for the inconvenience.

[BrainDead]

I have already adjusted the 2k Mercury texture so that it now accurately reflects the locations it depends on for my simple tour of Mercury.

Don't know if anyone even cares or not, but I'll upload the revised Mercury
zip package to the CML later tonight. The original texture needed to be
offset by approximately 80 pixels to the left. Just FYI. -BrainDead

[Cham]

Hey ! Bob IS BACK !

Nice to see you back, Bob, I was wondering ...

[BrainDead]

Hey ! Bob IS BACK !

Nice to see you back, Bob, I was wondering ...

Don't let yer nipples get too hard...

Sorry, but I've been very ill. Won't be around much longer but I still
love exploring the universe when I can. Thanks for the remembrance.

Love ALL of you space nuts.

Take care, Bob

[ElChristou]

Hey, Bob nice to see you!

Hope you the best for the unpleasant moment...
Take care Bob, later!

[John Van Vliet]

hi I just took a lok at my 8k Mercury map and compaired it to
http://www.solarviews.com/cap/merc/mer06.htm

and it is 195 pixles off
open in gimp and set x offset to -195 and save

[Hamiltonian]

(I noticed the Hun Kal crater at -21.4 longitude while it is by definition at -20, but no matter; I'm sure it's easier to nudge the terrain.)

Hun Kal is at -20 in the new update on CVS.
http://celestia.cvs.sourceforge.net/celestia/celestia/data/merc_locs.ssc