Tools to generate textures

[fhstoica]

Hi,

I have some tools that can be used to generate textures like the ones attached. I made a sample using a color map with only 3 colors, Red, Green and Blue, the same sample on grayscale only, and the normalmap, which I simply generated with the GIMP plug-in.

The colors can be changed, more can be added, the roughness can be increased or decreased. The attachments are just a sample of what can be done. Since the texture is generated using a Fast Fourier Transform, the opposite edges of the images match, and they can be easily tiled.

If anyone is interested please let me know and I will make the tools available to everybody.

[krilain]

Hello, are you the author of the gimp plug-in that produces those effects?

[fhstoica]

No way, I am not at the point of writing GIMP plug-ins.

Only the last image, the normal map, I generated from the grayscale image using the Normalmap GIMP plugin. I simply installed the plugin on my Linux distro using Synaptic.

I believe you can contact the original author at this URL:  http://code.google.com/p/gimp-normalmap/

I generated the images using a Fourier Transform of a 2D array of random numbers (filtering out the high-frequency noise), and plotted the resulting surface (seen from above) using POV-RAY.

[krilain]

Ok, thanks for the answer. It is not I wanted to contact the author of the plug'in at all. It was to know until what point you can control your texture production process in order to ask you to produce a wider set of samples with no hand working, which would be long I think.

[fhstoica]

This week I am a bit tied up with some work, but I will post the tools. Basically you need GSL (the GNU Scientific Library) for the FFT and then you will need POV-RAY. The 2D FFT code (GSL offers only 1D FFT if I remember correctly) is written in C++ and the code for generating the POV-RAY script is written in Python.

Basically you can specify a few Fourier modes by hand (or let Python generate them for you as random numbers), so it takes very little time to generate the textures you see. The color and the grayscale ones take about 5 seconds to generate on my machine (Athlon II X4, 3GHz).  You have very granular control over each step.

The normalmap requires hand work in GIMP.

I will post a short how-to on this forum, but I will write a more detailed document on what each script/program does. Will also generate more samples, and they require no hand work, just to launch a script from the command line.

[fhstoica]

Finally, I added the tools I mentioned. I also included a new sample texture with the tools, (I did not crop the image).

You'll have to unpack the archive and first modify the Makefile so that it points to your installation of GSL (http://www.gnu.org/software/gsl/), needed for the FFT.

If you work in Linux and have POV-RAY (http://www.povray.org/download/) installed you can uncomment the last line in the start.py file so that the same script will run POV-RAY as well. I am currently working on a Windows machine and I am running start.py under Cygwin. I have to run POV-RAY outside of Cygwin, and process the surface.pov file generated by the scripts.

The quick way to generate a texture is:

./start.py <random_seed> <central_frequency> <decay_power> <output_file>

At the moment it is set up to generate a grid of 128x128 and render the image as seen from above, making basically a contour map.

For example, the image I attached I generated with:

 ./start.py 8991 20 1 surface.png

The central frequency can be somewhere between 0 and 64 (since the grid is 128^2), and the decay power between 1 (for a rough image) and 3 (for a smooth image).  Feel free to experiment with these values. 8991 is just some value I used as seed for the random number generator.

I will write a more detailed description of what each tool does.

[krilain]

Thank you.

I will try this. It could be very useful for me for landscape purpose. I've to get rid off the first difficulty as I'm on windows and not on linux.

I'll give you feedback.

[fhstoica]

Thanks, I'll wait for your feedback.
You may know this already, but just to make sure, the stock installation of Cygwin comes with GSL included.

[krilain]

  Omg, I've been in trouble with cygwin. That sys is revenging for I've usually neglected it for 2 reasons, the first is I don't like a soft that tries to write in C:/ directly, I find this strange under the feeble Windows that in my opinion may get troubled for less than that. Second thing is I've always found unsafe to make a downloading bridge for hours (hours taken just for downloading very tiny packages...). In fact I've always thought that cygwin was made for schools where administrators can use a dedicated computer just for download purpose.

Ok, so as I said I've been in trouble, for I had to retrieve GCC I made the same time a "massive" download to the local disk (that was taking days so I had to abort). Then, I tried to install what I've got, but some of the packages were corrupted !... From this point, I've encountered badly encoded directory names (such as 04 ü˜vK箬Nû]ç§ÆÛ§„®è‡Ö­fjý…%«N¦2¦oZ+µ1ë=‰]ɱI —œ fµò¯«î¨U¿›.[W]× ...) that I try to remove right now. And I dont know if I mistake but I'm looking for about 4 Go gone in smoke in 20 minutes when I've let cygwin trying to abort the install....

That's a pity because I wanted really to test your stuff. I plan something that may ask for textured tiles.

Big recursive rm -r -R is waiting instead ....

ps: anyway a search on the web throwed me there : http://gforge.enseeiht.fr/scm/viewvc.php/SPa1/main.pdf?pathrev=106&sortby=author&root=spacify-dsml&view=diff&r1=73&r2=74 ... does that show some try to write files names in Tex???

[fhstoica]

Drat, I am really sorry to hear that you cannot install Cygwin.

One possibility is for me to try and port the 2D FFT program to FFTW instead of GSL.
That is because FFTW comes with pre-compiled Windows binaries and can be used from MinGW.
You can also install Python and POV-RAY for Windows, and then there will be no need for Cygwin anymore.

In the meantime, please let me know what kind of textures you would like. Please look at the Python script Generate_Texture.py at the self.color_map definition in line 15 of the script. This will tell you which colors will be used in generating the image. You can then tell me which colors to use and I will generate some samples.

It's not ideal, but it is a way I can help, and you can tell me what changes to make, until I get a painless way for you to use the tools directly.

[krilain]

Don't worry, in fact the problems come from the fact that I'm using the computer to test some modeling so that it was not a very good news to get this cygwin bug.

Anyway I think I've found the reason of this. Here for information : as far as I remember, I aborted a big part of a Tex package in download. When I asked cygwin after that to install all the packages I'd finally downloaded, cygwin possibly has met this uncomplete Tex package and unfortunately was unable to handle it. So it created a lot of directories named in Tex format which is properly undeletable with Windows - but , good point, removable in the cygwin console with rm. For my 4 Go, it is that I'd downloaded too much packages, moreover unuseful because I had most of them (like Perl) in spare parts somewhere else.
Ok, for the textures, what I would need it is quite simple. I'm looking for landscapes tiles that could in any maneer imitate (when melted properly) a top view over the earth.
Unless you're interested on training on this concrete case, I wouldn't ask you to make a sample because I still want to try another approach to compile your C file with the help of visual studio and the GSL library. I want this to work

[krilain]

I just post a feedback here. Don't worry about the previous post, it's outdated.

So I've finally compiled the c++ part with gsl inside. Let me tell you that I've again encountered some strange problems. I tried first with QT4, which has a so nice editor, but linking was impossible (using visual C in fact). Then jumped to Visual studio directly, and again encountered some weird issue. The good new, is that, I have been following the first steps provided in the UFOAI wiki for compiling the game and downloaded the great Code Block. This one compiled the file almost immediatly. It uses directly some gcc, that apparently helps. 

Ok, I have now to run it with your python script even if I wonder what new surprises are pending

I would like to add some information here about the UFOAI wiki pages dealing with textures. I've read some part, some days ago, so I'm not sure about the links but this one is an example : Wiki..

I discovered there, that there could be a "pick effect" when tiling a texture, just like in tiling sounds. That requires to remove the low frequencies from there, and a gimp plugin helps for that. Anyway if you are fluent in gsl as you seem to be, you may remove those frequencies by advance in your tool when you get the time for that.

ps : compiled version of GSL here : Geldreich compiled gsl

[fhstoica]

Hi,

I'm glad that you managed to compile the code, after a bit of digging I found that Python supports 2-dimensional FFTs directly via the numpy package:

http://docs.scipy.org/doc/numpy/reference/generated/numpy.fft.fft2.html

http://sourceforge.net/projects/numpy/files/NumPy/1.6.2/

I may be able to put everything inside a single Python script that you can run from the Command Prompt in Windows.
Anyway, I tested the executable you posted, and it works perfectly.

The roughness you are mentioning can be controlled via the last parameter, the "power". The higher the value, (2 to 5) the smoother the image. A value between 1 and 2 will result in a rough image.

I have to read a bit more about the "pick effect" you mentioned, but the low frequencies can be removed by choosing a central_freq different than zero (for example 10, to 20).

Please let me know if you encounter any problems running the Python script, it should work with Python 2.7.

[krilain]

I may be able to put everything inside a single Python script that you can run from the Command Prompt in Windows.

That's would be easier indeed. But why don't you use some more dedicated engine, like Scilab (powerful matlab clone) dedicated to matrix and including all FFT you could dream of

I have to read a bit more about the "pick effect" you mentioned, but the low frequencies can be removed by choosing a central_freq different than zero (for example 10, to 20).

Sorry that's more a "peak" effect. I'm not an english first language guy
As far as I've understood, it is the same effect that you meet when you melt 2 or more identical sounds, the low frequencies make blank sound...

Edit : I've finally obtained my first texture generated by your process, attached below. I removed the part with sys.argv entry at start.py, and I'm entering them manually. I removed also the "make" part, and I let start.py use the exe directly. I don't use povray inside the .py, I just let it generate the surface.pov and open the povray editor. That's fine
   

[fhstoica]

Well, done! You got it working now. The two diagrams you posted explain the flow of the texture generation process very well. You basically wrote the documentation for it.

Time to go a bit more into the details:

First, in the povray.ini file the line:
+W1024 +H1024
controls the width and height of the rendered image, in pixels. As it stands it is set to 1024x1024.

You will notice in the Generate_Texture.py script in line 128:

outstring += 'object{surfface scale<1.33, 1, 1>}\n'

This scales the surface horizontally (the x-z plane is the horizontal, y is the vertical) so that the final texture has the same numbers of pixels horizontally and vertically. I found the 1.33 value by trial and error.
Feel free to modify the parameters in this line if you want to get a different shape, but it is a good idea to keep the value for the y-direction to 1:

scale<x_scale, 1, z_scale>

At the moment the surface is shifted and scaled vertically so that it takes values between 0 and 1 along the y-direction. This way it appears flat when seen from a narrow-angle camera located high above the surface (line 88 in Generate_Texture.py). Changing the y_scale can make perspective effects visible, so it is better to leave that value unchanged.

As for the color_map, at the moment it is defined as:

        self.color_map       = \
"""[0.0  color Green]
[0.125  color Blue]
[0.25  color Red]
[0.375  color Orange]
[0.5  color Sienna]
[0.625  color SteelBlue]
[0.75  color Cyan]
[0.875  color Yellow]
[1.0  color Magenta]"""

It specifies at each contour level (between 0 and 1) which color to use. POV-RAY will interpolate the RGB values between these levels. The predefined colors are specified in the colors.inc file of the POV-RAY installation. They can also be found here:
http://www.buckosoft.com/~dick/pov/colors.php

You can specify the colors in rgb format, for example "color rgb<1, 0, 0>" or rgbf format, for example:

        color_map {
          [0.00, 0.33 color rgb <0, 0, 1>
                      color rgb <0, 0, 1>]
          [0.33, 0.66 color rgbf <1, 1, 1, 1>
                      color rgbf <1, 1, 1, 1>]
          [0.66, 1.00 color rgb <0, 0, 1>
                      color rgb <0, 0, 1>]

Again, very good documentation (for pigments, in general) can be found here:

http://www.povray.org/documentation/view/3.6.1/77/

I still have to rewrite Generate_Texture.py to include the FFT as well.