GIMP Converting rough heights to smooth altitudes

[CAgrippa]

I've been playing with GIMP, using RobA's fabulous tutorials, and enjoying it very much. I am trying to do a large-scale (continent-plus) map in roughly the style he describes.

I used FT3 to create a very nice heightmap, ranging from high peaks to deep oceans, all exported using flat colors for each level. To select each level, I've just used the "select > color" tool, and have created a layer for each such colored level. Thus I have layers ranging from "Abyss" and "Deeps" to "Peaks" and "Snowcaps." I know, from RobA, how to use any one or more of these to produce masks that can be applied selectively, and so forth.

Now what I want to do is to set a height level, which I believe for land needs to be 0 (low) to 1 (high), with an appropriate number for each layer, and then normalize or smooth or whatever across all of this. Then I can apply a gradient color green, and then do it again only at the higher levels and do it more brown, and so forth.

But somehow, I can't figure out how to achieve this.

I am hoping to use the Bevel or Emboss Distort effect, which (when I've gotten it to work) does produce beautifully sharp-edged high mountain ridges.

I also don't grasp at what point to apply noise if I only want to roughen the textures without significantly altering the heightmap.

Last but not least, I've seen tutorials that suggest ways to impart nice lighting effects to get the mountains to glow as if lit from the northwest, but these are for PS and don't seem to apply very well to GIMP, though I admit that I haven't fought with this part all that much.

Many thanks!

[Note: I'd be happy to upload the FT3-rendered JPEG, but I'm away from my computer on my iPad and don't have access at the moment.]

[CAgrippa]

UPDATE: Would RobA's script for gradients help with this? It seems as though it ought to....

[waldronate]

Silly question: wouldn't just saving the height field directly out of FT3 as something like a PNG let you work with it in the GIMP? Then you'd have all of the detail in the FT3 image directly in your PNG.

[CAgrippa]

Oh. Would it? I'll check when I get home -- that would certainly be nice. <sigh> So much to learn!

Thanks!

[johnvanvliet]

Gimp and Height maps do not mix well
The gimp is only 8 bit
( gimp 3.0 will handle 16 and 32 bit images)

That means there is ONLY 256 tones ( 0,255)
that will give you a DEM / normalmap that is STEPPED
you NEED to use at least a 16 bit image !!!

A 16 bit image has 65536 tones
Ushort / Unsigned = 0 to 65535
Short / Signed = -32767 to 32766
or a 32 bit floating-point image ( normally 0 to 1 with 32 decimal places )


i use different software to make a 32 bit floating point or 16 bit Unsigned "Noise" image "FBM" is one i like also segmentation of triangles works to get the original height map
then use some custom software to convert that to a NormalMap that will render Correctly on a sphere

Now what I want to do is to set a height level, which I believe for land needs to be 0 (low) to 1 (high), with an appropriate number for each layer, and then normalize or smooth or whatever across all of this. Then I can apply a gradient color green, and then do it again only at the higher levels and do it more brown, and so forth.

for that i would use "G'Mic" a terminal based image lib
-- you WILL need to build the current source code to reenable 16 bit output
G'MIC - GREYC's Magic for Image Computing: An Open and Full-Featured Framework for Image Processing


it sounds ( " 0 (low) to 1 (high) " ) like you have a 32 bit height map
for use in gimp
renormalize the different color layers ( deep sea to land ) .Normalize them to 0 to 255
and save as a 8 bit char image

then use gimp to colorize them

Gimp has a handy built in "colorize" tool that dose a great job

Gimp > "colors / map / sample colorize"
just have the black and white and the color one open