Celestia Forums

Hi

I have made a level7 VT for entire Spain and Portugal (not Canary and Azores islands). I hope you enjoy it. Download from:
http://www.mp-labs.com/celestia

Spain east coast:


Gibraltar:


Catalonia with the delta of Ebro:


Madrid, with the Pyrenees at far:


Regards
Manuel

Nice textures, Mac.

I?ve installed them and I?m impressed.

Good job, guy

See you at "home"

Hi,

thanks for those nice vt's.

Unfortunately now there is shift to my 32k spec map.... It seems, that your level 6 & 7 vt's "jump to the east" compared to level 1-5 of BlueMarble.

Ciao
Dora

hi Mac

this virtual textures are wonderful good work Mac

Very nice! Thank you for the great textures.

how about a custom spec map to go along with this so it doesent look funcky when combined with the BlueMarble tectur?

Guest...how about you try making one?

Regards...bh.

Manuel,

Excellent textures!
Many thanks!

Bye

NICE ,but at some point
all of us are going to have to get together and decide
on a server to host ALL of this. As a guess ~10_GIG+ .
Just a thought!

Hi Mac,

your VT's of Spain/Portugal are very nice. Unfortunately they are significantly misaligned relative to the BlueMarble data. Probably, you have found out already yourself. Otherwise I can easily provide ample evidence.

My question is what source of data you have used.

Normally, at such high resolution one has to run some (non-linear) stretching corrections here and there to optimize alignment. You apparently have not done that.

If you tell me the sources, I can have a look myself...

I would also want to eliminate the black border lines which is an easy task...The quality of the texture seems well worth some additional effort...

Bye Fridger

Fridger,I think that it is made up of images from the Modis sites (or Aqua and Terra).The bulk of it seems to be taken from this image
http://rapidfire.sci.gsfc.nasa.gov/gallery/?2003079-0320/Spain.A2003079.1315.250m.jpg
but others have also been used.Try going here
http://rapidfire.sci.gsfc.nasa.gov/gallery/
and then enter a search for Spain.This will come up with many shots of Spain and Portugal,they all have the black country borders on and red squares where forest fires were happening.Hope this helps Jestr

Hi.
It's not an easy task, and it's my first attempt of VT!
Sources are all from MODIS satellite images. I used 3 of them and combined it to take the sharp parts of each and make one big texture with the best of all. Also I try to avoid parts with clouds. This images are taken to show several forest fires, and they are marked with red squares. I removed all of them too. It's true that it could be not correctly aligned (about +/-90 km error), but that's the best I can made it. Also I had to work very slowly because of the limitations of my pc and the large size of the entire texture
I stretched it both horizontal and vertically and applied lots of filters to make the colours according to Blue Marble ones.

Here you have the site I used to get the sources:
http://visibleearth.nasa.gov/

Regards

I've been trying to do textures as well but been having problems with the alignment as well. I can't get it right. I think it has to do with the size of the image i'm trying to put over it.

It was my post, can could someone explain this non-lineair stretching?

t00fri wrote:Normally, at such high resolution one has to run some (non-linear) stretching corrections here and there to optimize alignment. You apparently have not done that.

By non-linear scaling, do you mean scaling the original 512x512 BlueMarble tile differently along the horizontal and vertical lengths before overlaying the new images on it? Or is it more than that? Redfish and I were talking about what non-linear stretching meant.

Brendan

Brendan wrote:

t00fri wrote:Normally, at such high resolution one has to run some (non-linear) stretching corrections here and there to optimize alignment. You apparently have not done that.

By non-linear scaling, do you mean scaling the original 512x512 BlueMarble tile differently along the horizontal and vertical lengths before overlaying the new images on it? Or is it more than that? Redfish and I were talking about what non-linear stretching meant.

Brendan

Redfish, Brendan,

here come some more explanations:

Consider for simplicity just the horizontal matching of two textures by rescaling one of them.

Let the pixel locations p and width of the texture L be

0 <= p <= L

linear rescaling means matching via a global rescaling factor s

p' = s*p, L' =s*L

Such that the pixels are mapped linearly.

What often happens, however, is that after matching the features near one end of the texture, the matching gets worse e.g. in the middle...What is actually needed in such cases is a non-linear rescaling,

p'=s(p)*p, L'=s(L)*L

Well known problematic examples are the Viking/USGS (colored) Mars texture and the MOLA elevation maps.

There are various possible strategies to determine the best scaling function s(p).

-- Fiddling around...
-- using ImageMagick scripting (e.g. Perl,...)
--...

Bye Fridger

Thanks Fridger. I happen to be learning Perl and have Imagmagik installed, so I'll see what I could do.

Brendan

I'm not that mathematically trained, but will give it a try. I got holidays anyway!

Hi everyone,

the discussion about the spanish hr-texture touched questions I'm asking myself for some time and maybe it would be nice to have them answered somewhere cohesively. Or has someone already done it but I was just too lazy to find out?
What kind of map projection (mathematically !) is used in general for the preparation of the textures, say e.g. blue marble, is it a cylindrical equal-distant type or what?
The answer of the above question determines how to solve the problem of mapping e.g. an arbitrary satellite picture onto the textures. Raw pictures are frequently shot from obligue angles and have to be rectified (nonlinear operation, see t00fri ) to azimutal projection, which then has to be recalculated/transformed to the general mapping,- again a nonlinear operation. This is somewhat difficult because I think one has to provide reference points for the transformation, i.e. points in the pictures with known coordinates.
Comments ? Has anyone heard of free software for doing those jobs ?

ukam

Celestia uses "simple cylindrical" projections, aka "Plate Carr?" (which seems to have various spellings)