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Thread: Help please - colour overlay

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    Guild Adept icosahedron's Avatar
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    Post Help please - colour overlay

    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.
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      jfrazierjr is offline
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    Quote Originally Posted by icosahedron View Post
    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.
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    Guild Adept icosahedron's Avatar
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    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.
    Mapping a Traveller ATU.

    See my (fantasy-based) apprenticeship blog at:

    http://www.viewing.ltd.uk/cgi-bin/vi...forums&sx=1024

    Look for Chit Chat, Sandmann's blog. Enjoy.

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      jfrazierjr is offline
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    Quote Originally Posted by icosahedron View Post
    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..
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      torstan is offline
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    Do you have the image you are applying the map to?
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      Redrobes is offline
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    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.

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    Redrobes, what is your "texturer"?

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      Ascension is offline
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    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.
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    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.
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    Quote Originally Posted by Ascension View Post
    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>

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