Celestia Forums

Celestia inspired me to start working on textures for my project on the planet Furaha (see http://www.planetfuraha.org). I started in what me be an odd way for most people here, as I had little experience with graphics programmes but was fairly familiar with Matlab and its cartography toolbox. So, instead of cutting and pasting a texture, I wrote some programs to cut, paste and blend height maps. There are several examples on my site; here is an example:

Later I wanted a neat texture as well, so I have now taken up Photoshop and am building a texture. In doing so, I thought it would be nice to add snow depending on the season, and I would like to show my first attempts to hear from people here whether the process I thought of makes any sense. I remembered that the elevation above which you can find snow and ice increases as you get nearer the equator. Now take the elevation over a meridian going from the North pole to the equator, and plot the resulting line as if the planet were flat. The blue lines in the following graph are just a few of such elevations across various meridians, going from North to South; the poles are at the edges of the chart (horizontal distances are in arbitrary units). Now draw a line that starts at an elevation below zero at a pole, increases towards some high value at the equator. Anything above the line will be covered in snow. The lower the starting elevation at a pole, the more land will be covered with snow. The red and green lines represent such thresholds (one for summer in the North, and one for summer in the South).



Now these lines are very simplistic, and should perhaps be supplanted with something fancier. Does this make any sense? Have others done something similar? I will show the first results in a new post (as I cannot put 4 attachments here).

Here are the results for one setting:



And this is what you get by reversing the effects for the two poles:

My God,

Sex is SURELY the better alternative

Fridger

t00fri wrote:
My God,

Sex is SURELY the better alternative

Fridger

I can think of lots of things sex is a better alternative for; things such as work and dentistry come to mind... But what's the reference here?

Ah adding snow, ive been practicing that lately for my andorian textures, if you want i can tell you haw to do it in gimp to achieve results like this:



though the image seems to be resised the snow is as detailed as the rest of the map.

There is a way to create snow and ice on mountains if thats what you are looking to do. I was going to write a tutorial on how to do this but never did get around to it. Maybe its time to post what I know.

If this is what you are looking for let me know and I will get started on it.

Don. Edwards

Don. Edwards wrote:If this is what you are looking for let me know and I will get started on it.
Don. Edwards

Yes please! My technique is a bit elaborate, but now that I've written the program (about 2 hours work) it does not take too long, but I am most interested in hearing about other techniques. My 'solution' requires Matlab, and if yours can be used by more people it will probably be more useful.

This isn't about adding snow, but I finally finished stage 1 of a texture for Furaha, and so here is is (half size). As this is my first texture, I welcome comments and suggestions.
Note the large desert areas; Furaha is larger than Earth, and with continents this size, their interiors might turn out to be very dry places.



The original is 4096 pixels wide, and this one is 900 pixels wide (what is the maximum by the way?).

Note the large desert areas; Furaha is larger than Earth, and with continents this ize, their interiors might turn out to be very dry places.

Why is this stage 1? Well, because I still need to produce summer and winter versions, and because there are hardly any lakes or rivers. Instead of simply drawing them in, I think I will write a program finding water catchment areas and the most likely drainage channels.

Coen wrote:The original is 4096 pixels wide, and this one is 900 pixels wide (what is the maximum by the way?).

As large as your computer can handle without becoming too slow.
Celestia cuts large planetary surface textures into pieces which are small enough to fit into the texture buffer of your computer's graphics card.

Celestia also supports what it calls "Virtual Textures", composed of many small tiles. VTs can be more efficient in disk and memory usage than a single large image would be, since you don't have to provide high resolution images for all the areas that are identical -- like ocean surfaces. Pointers to VT documentation are available on the Celestia MotherLode about half-way down the page http://www.celestiamotherlode.net/catal ... ation.html

As large as your computer can handle without becoming too slow.
Celestia cuts large planetary surface textures into pieces which are small enough to fit into the texture buffer of your computer's graphics card.

Sorry to have caused a misunderstanding. I know about the 2K 4K 8K etc. system, and how Celestia divides large maps into smaller pieces. Here I only wondered about the size of the images in the forum: I found that part of an image of about 1000 pixels wide was cut off, and the image that I did post, of 900 pixels wide, was complete. That's all I meant.

I don't believe the Celestia forum software imposes any size limit on external files, only on those you upload to shatters.net; still, it's best to use thumbnail images which link to larger ones so as not to force people to repeatedly download large files that they've already seen.

Right! I'll do that next time. Thanks.

You truly are on your way if this is your first attempt. But there are a few things to learn as of yet.

1. Always think big. Even if your computer can't handle using, say a 16k texture. Its always better to work with as big a texture you can handle with your software. You can always downsize the texture later to a more manageable size for use an distribution. Trust me on this it is so much better to be able to zoom in on something and fix it at higher resolution.

2. Coloring, I know you aren't finished with the texture yet but you need to think what it would really look like if your planet were out there hanging in space. Don't be fooled by all that pretty space art out there. Earth like planets are pretty much all going to look pretty much the same from space. What I mean is that the oceans aren't going to be pale or turquoise blue and the land isn't going to look bright green and verdant. Its simply the laws of physics that make these choices so you can try and fight what it should be like versus what you want it to look like. So I am doing something I don't normally do. I am not doing this to step on your toes but to help teach you the subtleties of creating truly great textures. I only do this for those I think are on there way to becoming master texture makers. So here it is. What your end product should look like if it were real.



I know it looks dark and if it were my own texture it would be just a little darker. But by taking the oceans to their truer darker coloring it makes all that coastal water in the shallows pop out and take notice. I did all this in just ten minutes. Of course I have been doing this for years now but once you learn how to do things it becomes second nature.

3. Ok, last point. The land masses. You have done a great job with them. You have the deserts at about the right latitudes that would be expected. At least for a planet between the size of the Earth and maybe up to 9000K in diameter. If the planet were any bigger you would start to see more Hadley cell in the atmosphere and you would have different bands of desert and vegetation at different latitudes. The only thing I might recommend is to move the two biggest continents on the right side of the image down a bit. This is to center there desert regions with the other deserts at that latitude and also to pull them away from the polar regions. Mainly because Celestia is going to stretch the northern big continent out of shape and into the polar areas. This will look strange, trust me on that. Also I tried to use my trick to make snow for mountains on your texture. Unfortunately because of its lower resolution and the fact that there really aren't any mountainous regions that stand out I wasn't abler to do anything.

All in all you are on your way to becoming a good texture artist. Trust me on these points. I once was a beginner just as you are now. I learned allot as I went. I got lots of pointers from members here in the forum and took what i learned and went with it. I also found a few tutorials out there. Some were helpful others not so. Its all try and error anyway.

One last thing, just so you can see what I mean about the coloring of sea and land here is what your texture looks like all skinned out in Celestia with the changes I made.


Nice place, i would live there.

Don. Edwards

Don. Edwards wrote:So here it is. What your end product should look like if it were real.



I know it looks dark and if it were my own texture it would be just a little darker. But by taking the oceans to their truer darker coloring it makes all that coastal water in the shallows pop out and take notice. I did all this in just ten minutes. Of course I have been doing this for years now but once you learn how to do things it becomes second nature.

Can you post a brief tutorial describing how you did this?

A tutorial, hmm. I haven't had the best luck making them but I guess I can try. I will be posting it in another thread though. I believe in keeping threads as on topic as possible. So I will create a thread dealing with threads in the near future.

Thanks for the interest.

Don. Edwards

Don. Edwards wrote:Nice place, i would live there.
Don. Edwards

Thanks! Not just for thinking Furaha is a nice place, but for the praise as well, and mostly for the effort you have put into making it better. It is much appreciated.

Here are some specific remarks concerfning the points you addressed:

-About image size: I am starting to understand why bigger is better in textures. But this was my first texture, and when I started it I didn't really dare go for a really big one yet.

-About the colours: now this is very interesting. I had used the 'Blue Marble' maps as my guide to colour use. While working with them I found that it was sometimes hard to see what I was doing because they are so dark! Still, up until yesterday the Furaha map was almost as dark as your version. Only then did I wonder whether this dark scheme was faithful to nature. I even tried to find something factual on this, but failed (I probably did not look not hard enough). And then I came across a 'minority' colour scheme on the Celestia Motherlode named 'real color Earth surface'. So I then thought 'why not?' and brightened everything.
The good news is that it will not be very difficult to go 'over to the dark side' again. I will pose the question how we know which brightness is right on your new tutorial thread; it may be more useful there.

-About the position of the continents: don't worry, the apparent change in shape will not startle me, as I know how the continents look like when depicted on a sphere. They more or less started out that way! This means that a long time ago I made a rough sketch of the shapes, drew the shapes on an actual globe, and used this to jot down the actual coordinates to obtain digital coastlines. The digital elevation map and the texture came much later. But all the time I have looked at global views of Furaha, using Matlab or -later- Celestia. So I know that it is the shape on the texture that is the distorted one, not the spherical one.
But if you think that the deserts are placed too far to the North, I may have to alter their position.

Finally: I am most curious to learn how your ice & snow trick works, especially as it does not seem to involve a height map (or does it?). I will post back here with some examples how mine works with an Earth height map.

Thanks again!

This is just to return to the main topic...

I thought I should try my snow routine on Earth rather than on Furaha, as I can could then compare the results with what they ought to look like. Compare the result with one of the images here (april is close): http://earthobservatory.nasa.gov/Newsro ... hlies.html

The image I made was monochromatic brown to start with, and white was added depending on height and latitude to simulate snow cover. It seems to work reasonably well for many areas, but is completely off for others. The Tibetan plateau is obviously one such area. The very simple calculation I used does not even take the amount of precipitation into consideration, and that might be the main reason for the difference: If the plateau is very dry, then there can be no snow cover.

Anyway, the programme does produce patterns that superficially resemble real life patterns, so I think I will use it. Anyone else is free to have it, BUT it works in Matlab, and does NOT work on a texture, but on an elevation map. There may be better and easier solutions...

Have you considered including seasonal changes in snow cover and ground (vegetation) color?

selden wrote:Have you considered including seasonal changes in snow cover and ground (vegetation) color?

Oh yes! Adapting the model to show different seasons is easy. It is a simple question of making the snow border and/or the width of the snow transition zone creep towards the equator. I could also put in a bit of randomness to simulate weather rather than climate.

I also thought briefly about making the vegetation change colour with the seaons, but that is hypothetical only sofar. I haven't thought at all yet about which areas should change colour in what direction in which season.

Now that you mention it, there are 'Darkgrasses' (see the section on 'grecs'), and these might become paler in winter on some dry steppes. Some vegetation is purplish rather than green (see the section on cathedral trees in particular), and the 'Sargasso floats' aren't even on the website (tangled vegetation clogging shallow warm seas).

Sofar I have been very Earth-conservative in assigning colours to the texture. Just starting to feel my way around.

Well for Earth anyway we do have 12 seasonal maps already made by the BlueMarble team, color adjusting not counting of course. There are some very rough areas in their textures that I had started working on almost 2 years ago. I had four or five months taken care of before I stopped the work. I will probably go back and finish them but I have to nail down the exact color changes made so each one is done the same.

Your plan with the info should work out fine. Just keep in mind your mountainous areas and dry zones. But remember that even dry zones get snow. Most of the high desert regions of western North America does get snow at some point in the winter. Sometimes its the only precipitation for most of the year.

If you really want to be hyper realistic than you can take into consideration the things I have done with my Terraformed Mars texture. Estimate the amount of Hadley cells per hemisphere, and atmospheric density, the trade wind routes and how high altitude landmasses effect the way the wind and weather will move around the forms and the end result for vegetation and rain fall, and ect... It can get incredibly complex in the end. But it also opens one's mind into just how complex these systems can truly be.

I wish you luck and hope to see were you take this.

Don. Edwards