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icosahedron
11-11-2009, 10:16 AM
I've been looking at Ascension's Planet tutorial (again :) ) and I'm trying to replicate the land colouration of his Earthlike planet in Gimp.

Without success.

With a few clicks of the mouse, using some form of gradient overlay, Ascension takes a greyscale cloud on his land area and converts it to a coloured terrain that merges from white ice at the poles, through a green temperate zone, to a yellow desert at the equator.

Can anyone give me step-by-step instructions on how to do this in Gimp, cos it's got me beat?

Thanks.

jfrazierjr
11-11-2009, 11:50 AM
I've been looking at Ascension's Planet tutorial (again :) ) and I'm trying to replicate the land colouration of his Earthlike planet in Gimp.

Without success.

With a few clicks of the mouse, using some form of gradient overlay, Ascension takes a greyscale cloud on his land area and converts it to a coloured terrain that merges from white ice at the poles, through a green temperate zone, to a yellow desert at the equator.

Can anyone give me step-by-step instructions on how to do this in Gimp, cos it's got me beat?

Thanks.

I don't have time to test it right now.. but if you already have the height map, you need to create (or find) a custom Gradient that goes from one end of the spectrum of color to the other. Then, on your image, select the heightmap (or a copy so you have the original!!!) and select Color->Gradient Map or something like that... This will take your b/w image and map the gradient you are using based on the colors.

icosahedron
11-11-2009, 12:41 PM
Thanks for the reply, JF, unfortunately that's not what I was looking for just now - though it's a useful tip for later, I'll try to remember gradient map.

Your method applies colours to different altitudes, I want to apply colours to different latitudes - polar colours, temperate colours and equatorial colours.

jfrazierjr
11-11-2009, 01:33 PM
Thanks for the reply, JF, unfortunately that's not what I was looking for just now - though it's a useful tip for later, I'll try to remember gradient map.

Your method applies colours to different altitudes, I want to apply colours to different latitudes - polar colours, temperate colours and equatorial colours.

You can acomplish the same thing by creating a "height field" with black on top and bottom fading to white in the center (or visa versa) and then run the gradient map. One way to do this fairly easily and somewhat uniformly without as much hard line bands is to create a 50% grey overlay layer and use the dodge (lighten) and burn (darken) tool to "paint" in the color as I stated above.. this will then allow you have some control over exactly how the transitions form.. then blur the layer a bit to blend, run the gradient map.. poof..

torstan
11-11-2009, 02:20 PM
Do you have the image you are applying the map to?

Redrobes
11-11-2009, 03:39 PM
I would do this with my texturer but I will tell you how this can be done with gimp like jfraz has said. I think you need to combine the two.

Create a greyscale gradient to go from light at poles to dark in equatorial regions. Then take the greyscale height image and add them together or average them or multiply them. Ensure that if you add them then the addition does not wrap around so that lowland hot areas get so bright that it wraps back to black again ! You may need to adjust the contrast of the lattitude gradient to something smaller.

Anyway the result is that you want polar regions to be cold and high regions to be cold. So that your lattitude map is equivalent to adding extra height at the poles OR that the height map adjusts the temperature so that its colder in high regions.

So once you have the two gradients modulated together then apply the greyscale gradient fill so that cold is white through browns and then greens to sand colours where real hot for deserts.

guyanonymous
11-11-2009, 03:58 PM
Redrobes, what is your "texturer"?

Ascension
11-11-2009, 06:07 PM
Y'all are over-complicating it. I just put a gradient overlay on top and set the blend to hard light. Gradient maps are something completely different and would be used for heightmaps and not for climate zones. The gradient produces "banding" but, to me, that's no big deal.

Notsonoble
11-11-2009, 11:00 PM
Ascension: The problem is Gimp doesn't have the gradient overlay effect out of the box...

icosahedron: http://registry.gimp.org/node/186 grab this script... If you use it on high res images though... be prepared for long execution times.

RobA
11-11-2009, 11:55 PM
Y'all are over-complicating it. I just put a gradient overlay on top and set the blend to hard light. Gradient maps are something completely different and would be used for heightmaps and not for climate zones. The gradient produces "banding" but, to me, that's no big deal.

So in gimp wouldn't that just be a new layer filled with a gradient, masked, and set to hard light?

-Rob A>

Ascension
11-12-2009, 05:29 AM
Exactly. I don't know what all Gimp has but a new layer with a mask and a blend does the trick.

icosahedron
11-12-2009, 07:02 AM
Thanks for the responses guys, but I'm very much a beginner with Gimp and most of this talk is going over my head.

I haven't even read RobA's famous tutorial yet, cos I didn't think I was ready for it. I wanted to get the hang of drawing up a planet before I focussed down to anything like realistic terrain.
Getting basic latitude colour ranges is my first baby step into terrain creation.

I don't have a map I'm working on, I'm just playing with some of the tools to see what they do, so I created a random coast outline. Basically, I'm just trying to add one small step to this:

http://www.cartographersguild.com/showthread.php?t=7700

so that all my land isn't plain green from pole to pole.

I don't know anything about Gimp scripts either, but I can snag that one and see if I can figure out what to do with it, thanks. :)

torstan
11-12-2009, 12:04 PM
Are you looking for something that looks like this:

18574

Here's the zipped .xcf file if you want to see how that was built. I can walk through the steps too.

18575

Karro
11-12-2009, 12:07 PM
Shouldn't there be two bands of yellow (desert) terrain? One on the northern tropic and one on the southern tropic, with a tropical green between the two?

torstan
11-12-2009, 12:17 PM
Indeed there should, but this was the gradient I had lying around. The method would be the same with a better gradient though.

icosahedron
11-12-2009, 01:47 PM
Yes, Torstan, thanks, that's exactly what I was trying to do. I'll have a look at that xcf. :)

I found the gradient editor today, but I couldn't figure out how to work it. I'll try reverse engineering your xcf to start with.

Notsonoble
11-12-2009, 01:59 PM
Yes, Torstan, thanks, that's exactly what I was trying to do. I'll have a look at that xcf. :)

I found the gradient editor today, but I couldn't figure out how to work it. I'll try reverse engineering your xcf to start with.

Ah... the dreaded gradient editor... I've played with that monster alot. I feel a tutorial coming.

torstan
11-12-2009, 02:30 PM
I find that it helps to get a gradient that has the right number of sections, duplicate it and then use the right click options on each section to edit the start and end point colours.

Remember that to edit a section on the gradient - click the section so that it is highlighted in blue across the bottom. Then right click and edit the colours of the left and right points. In the Load colour... section you'll find the option to match the colour to the nearest point. That should help you out.

Notsonoble
11-12-2009, 03:13 PM
http://www.cartographersguild.com/showthread.php?t=7875 <-- very basic example of how to manipulate the gradient editor in gimp.

icosahedron
11-12-2009, 03:47 PM
Torstan, you've built this up in a different way than I do. I can see the layers, but I have no idea how they're composed.

After a lot of trial and error, I discovered how to place the land shape and the gradient side by side - it seems to be a gradient pattern as the main image with the land shape as a mask (first time I've used a mask).

However, I'm not sure how those embossed layers were made and why there are two of them. What's a pasted layer?

Told you I was basic. :)

Edit: thanks for the Gradient Editor tutorial Notsonoble. That's how I figured it should work. Not sure what I was (am) doing wrong, but when I tried to change the colours of the section endpoints it kept working on the absolute endpoints instead. I'll go back and have another look at it.
Copying an existing gradient and then changing the colours might help. Thanks for that idea. :)

torstan
11-12-2009, 03:55 PM
Ah, no problem at all.

The layer mask means that you're only going to see the areas that are white on the mask. So the layer mask on the gradient pattern means that you're only showing the land colours over the land areas - so you won't have a green sea.

The emboss layers were taken from the image you have in your tutorial. I just copied in your green land layer. I then desaturated it (Colours->Desaturate).

I place this layer over the gradient layer and set the blend mode to soft light. This lightens the gradient of colours where the 'embossed layer' is lighter and darkens it where it is dark. I duplicated the layer as this increases the lightening and darkening effect. So the embossed layers give you the light and shade, the gradient layer gives you the colour.

torstan
11-12-2009, 04:04 PM
Also, I got the mask by using the select by colour tool (shift-O) and clicking on the black sea area that you have. I saved the selection (Selection->Save to Channel) and used that when I applied the layer mask (right-click->Add Layer Mask... and then use the Mask from Channel option).

icosahedron
11-12-2009, 04:45 PM
Thanks Torstan. That's a different method of using a mask than I tried, but it seems to give a similar result. This blend stuff is new to me, but I'm getting there.

I played with the gradient editor again and made a gradient I called 'Latitude'. It needs some work, but I've got the basic idea. The sections weren't blue-highlighting before. Sometimes I have to double-click. My mouse might be wearing out, I've noticed a few false clicks lately.

Just one more bug to iron out - my embossed layers are currently partially transparent, giving the land a washed out look cos I did a black to alpha so I could see through them. I'll work on them some more using the suggestions above and then post what I have. :)

torstan
11-12-2009, 04:50 PM
Ah, you probably don't want to make the emboss layer semi-transparent. I'd suggest playing with the different blend modes. They're very powerful and will really help get the results you are after.

icosahedron
11-12-2009, 06:19 PM
Yep, I didn't understand anything about Layer modes. I just found that dropdown and played with that instead of running black to alpha. Makes a huge difference.

Here's what I'm getting now - a far cry from my plain green. :)

I just need to play with the gradient some more. I'm happy with the polar and temperate regions, but the tropics are too stripey. Maybe I should cut out the equatorial forest altogether. Not quite sure how to fix it, but I'll probably know it when I see it.

Thanks for the help guys. :)

torstan
11-12-2009, 06:30 PM
You can always use the smudge tool on your colour gradient layer to move the colours around. That should help to avoid the overly stripey look.

Otherwise, that looks really nice. Good work!

icosahedron
11-13-2009, 05:41 AM
I tried two more things before I turned in last night, just to make it look prettier, but I found problems with both additions.

1. I tried to replace the plain black background layer with the cloud rendered blue I used in my tut, but the land looked 'floaty' because I hadn't been able to feather the coast this time. With three, possibly four different coast patterns now I'm not sure which to feather, or whether they all need feathering. I'll try them out when I get time later.

2. I tried to paint a few mountain peaks white, but found that even if I painted on the gradient layer, supposedly underneath the embossed pattern, the white still came out on top of the embossed pattern, obliterating the mountains. I can't figure how to paint underneath the embossed layers. Maybe it's just a problem with white? The arctic regions seem to lose pattern, too. I'll experiment later.

Maybe I'm ready for those regional map tutorials now...?

I wasn't entirely happy with the smudge effects, but that's something else to work on. I'd welcome alternative suggestions for correcting the stripiness.

Cheers.

torstan
11-13-2009, 09:21 AM
Yep, you might be past those regional tutes now :) ...

1. you can blend the sea with the land by blurring your layer mask. This will smudge the hard edge and help a smooth transition between the land and the sea. Is this what you mean when you say 'feathering'? If not, can you post your current version and say what it is that you don't like?

2. White. Yep, it's a problem with extreme values. If you have white or black, soft light layers won't touch them. If you have a light region in your lower layer, then the light regions of the soft light layer will have more effect than the dark regions. If you have a dark region in the lower layer, the dark regions have more of an effect than the light regions. If it's white, then the light regions lighten it - but it's white so you don't see anything - and the dark regions have no effect.

There are a couple of solutions. First, you can use a darker shade than pure white. Try something like an 80% grey - perhaps tint it a little blue. The emboss layers should lighten up the highlights to almost pure white and the shadows will still show.

The alternative is to duplicate your emboss layer and set it's blend mode to multiply and a low opacity, say 20%. That will lock in shadows independent of what the lower layers look like.

3. With the smudge - make sure you use a soft brush so that you don't get hard edges on it. Post what you've got and why you don't like it and I'm sure someone here will be able to offer a solution.

icosahedron
11-13-2009, 03:05 PM
Past them??? I doubt that.

Thanks for the explanation and suggestions, Torstan, I'll try those out and see what happens. :)

In my first efforts, when I was handling the Colour-Select and manipulating the land and sea, I had the 'feather' tickbox checked at the bottom of the toolbox window, and I found that this softened the coast similar to a blur. I'll try the blur instead and post some examples.

I'm tending not to save stuff at present so I don't clutter my machine with trials, besides, redoing the stuff helps commit it to my own memory. Having said that...

I was trying out various feathers on the coastlines, and I got to wondering whether I could do some sea ice. So I had a go.

Instead of the plain black layer at the bottom of the stack, I made a layer called 'sea'. I put my friesian cow land/sea pattern on it, colour-selected the sea part, then applied the 'square wood frame' gradient to the sea with bi-linear triangular wave formatting.

This gave a coloured bar top and bottom in approximately the right place. Then I took the eraser and erased the straight edges to a suitable shape, I then colour selected the wooden bar with enough threshold to capture all the wood but nothing else and applied cloud and emboss to the selection. I then adjusted the brightness and contrast to look like ice.

Finally, I colour-selected the remaining transparent sea, applied clouds, colourised it, and feathered it.

I'm quite pleased with the effect, though there's still something not quite right with the feathering on the coasts, it looks like a drawn outline.

Edit: BTW, where's the pic gone from post #25?

RobA
11-13-2009, 04:52 PM
BTW, where's the pic gone from post #25?

Seems to have been replaced with a 1x1px gif. Can you re-upload?

-Rob A>

icosahedron
11-13-2009, 06:18 PM
Yep, re-uploaded.

Here's one that gets rid of the 'drawn outline' effect, but has the land 'floating' on the sea.

torstan
11-13-2009, 06:24 PM
Looks like you've got a good handle on the different techniques there. It looks a little fluorescent for my tastes, but that's easy to alter with the Hue Saturation Brightness... controls in the Colour menu.

I'd tend to keep the land and sea on different layers, the land above the sea, and use the layer mask to define the land. If you use repeated selections with feather each time, then you're coastline will degrade over time, each time you use a selection tool with feather. Layers help you work like this non-destructively.

Looking good though.

Edit: the new version is better - not neon at all. And I have no problem with your land/sea border.