Geomorph - FAQ



What is the difference between the subdivision 1 and the subdivision 2?
The subdivision principle is explained in the introduction.

Subdivision 1 uses the "exclusive or" (NOR) instead of add and subtract for moving the altitude of the points on the surface (making "hills" and "holes"). while subdivision 2 uses add and subtract. Subdivision 1 is a lot faster because the "NOR" doesn't involve managing the overflows (over 65535) or the underflows (under 0). Because it's faster, it is the process used by the default height field pen.

Subdivision 1 height fields seem more rough, like if they were stratified with a lot of noise. Sometimes they look more insteresting than subidivision 2 height fields.

Subdivision 1, however, gives less control over the result than subidivision 2. Subdivision 2 provides parameters to control the distribution of the hills and holes, so that they are not too regularly scattered on the ground plane. It is also possible to control the amplitude of wave lengths composing the heightfield. A 0 ampiltude means that the corresponding frequency is removed. For instance, removing high frequencies (wavelength of 2, 4 and 8 pixels) is roughly equivalent to smoothing the image with a radius of 8 pixels by using the toolbox.

What is the use of the "seed"?

The "seed" is a number used as a starting point for the pseudo-random number generator of the system.

Geomorph frequently requires random values, for instance when it displaces the height of a point in the subdivision generation processes, when it displaces a bump on the ground in the surface sum generation process, or for creating noise.

Without these random displacements, it wouldn't be possible to create realistic height fields. If you want an example, set the "XY displacement" parameter to 0 in the progressive sum of surfaces options subdialog

Giving a random seed, written in the "geomorphrc" configuration file, allows to reproduce the results at will (this is why it's pseudo-random, not truly random). When you start Geomorph, or when you type a given number as seed, you should always get the same results.


Why did you choose the PNG format for Geomorph?
A high quality height field requires values stored on 16 bits for each pixel, which means 65536 shades or altitude levels. Most images have 8 bits for each color (or channel), which means 256 shades.

Height fields are monochrome, so using a 8 bits image format for storing them means a reduced scale of 256 altitude levels. This can give a stair effect on rendered landscapes.

PNG is one of the few format managing 16 bits per channel. It is recognized by many programs, including Povray, naturally. It offers a lossless compression. It allows to store comments and arbitrary parameters beside the image. For instance, Geomorph write in its PNG images if they are "tileable" (if they wrap) or not, and the cameras parameters used in the preview dialog. And last but not least, it was created as a royalty-free open standard, which should avoid situations like the one which happened with the GIF format a few years ago.

How can I import external images into Geomorph?
You should use a software which recognizes the file format of the external image, can scale it to a suitable size and can save PNG files.

Geomorph reads 128, 256, 512, 1024, 2048 or 4096 pixels wide square images. It doesn't scale or crop images. However, it converts RGB to greyscale images, and 8 bits (256 shades) greyscale images to 16 bits images (65536 shades).

The Gimp is a good choice to scale or crop most 8 bits / channel images, RGB or greyscale, and save it in the PNG 8 bits / channel format that Geomorph can read.

Using the "smooth"  tool with a small radius in Geomorph would blur the apparent stratification of a newly converted 256 shades image to a 65536-shade image. Use the "noise" tool to add high frequencies, for a more natural look.

How can I edit 65536-shade images created by Geomorph without losing the shades?

Geomorph does probably not fulfil all the requirements of height field editing. Maybe you'll want to use another editing tool.

The Gimp v. 1.x and 2.x reads Geomorph images, but reduces their tonal range from 65536 shades to 256 shades (16 bits to 8 bits).

You can try Filmgimp (now Cinepaint - see, a branch from an older version of The Gimp (1.0.4). It is adapted for film editing, but reads and writes PNG 16 bits file format. I didn't play with it a lot, though.

I don't know any other free program which edits images with 16 bits per channel.


The 3D preview disappears sometimes. What can be done?

This problem seems to be related to KDE. So far, it has not be seen under Gnome. I don't know the source.

The solution for now is to click on the "Refresh" button of the preview.

The preview dialog is not displayed at all when starting Geomorph, and there is a message saying that OpenGL is not available. Is it normal?

This has been observed in 2 situations:

1. Geomorph 0.30 is used with a recent Nvidia card and the proprietary driver. The solution is to update Geomorph to version 0.31 or later. Version 0.31 and later use the libgtkglext library instead of libgtkglarea, which fixes the problem.

2. Maybe the "glx" module (the 3D layer) is not loaded by the X-Windows system. Check if "glx" is specified in the "Module" section of your configuration file /etc/X11/xorg.conf (if you use Xorg) or /etc/X11/XF86Config or /etc/X11/XF86Config-4 (if you use XFree86). This section should look like this:

Section "Module"
    Load "dbe" # Double-Buffering Extension
    Load "type1"
    Load "freetype"
    Load "extmod"
    Load "v4l" # Video for Linux
    Load "glx" # 3D layer
    Load "dri" # direct rendering

If "glx" is specified, check in the log /var/log/Xorg.0.log or /var/log/XFree86.0.log if it is successfully loaded.

The "glxinfo" command executed in a X console, if it is available on your system, would show you if the GLX extensions are available.

It the GLX extensions are available and if the preview is still not displayed, please contact me.

How can I activate or unactivate the direct rendering (hardware acceleration)?

The hardware acceleration of the display system is provided with the DRI module ("direct rendering infrastructure") of the video card driver.

The hardware acceleration could speed up the terrain preview rotation or translation, by accelerating the OpenGL calls. However, it doesn't have any effect on the refresh speed of the height field. The preview mesh is recalculated after any change in the height field. This is the heaviest part of the processing, and it takes place before any call to the OpenGL library.

Futhermore, the activation of the DRI module could produce these problems:
Geomorph allows to specify if direct rendering is activated or not, only for this program, without any effect on the other applications. Because of the low benefits and of these problems, Geomorph is installed with DRI unactivated. However, you can try to activate it by using one of these methods:


In the dialog of the XYZ tool, the list of the available documents does not show the last document I opened or created. How can I refresh it?

Click on the tool icon to refresh the list of the open documents.

This behaviour could be seen in the merge tool or in the "Filter with an open document" option of the shape filter .

I added high frequency noise to the height field, but I cannot see it. How can I see it?

The high frequency noise is not displayed in the 2D image, and is very difficult to view in the OpenGL preview. To see it accurately, it is required to execute a Povray scene.

Why? For instance, suppose that the height is roughly proportionnal to the ground width. On a 512x512 image whose maximum altitude is between 214 and 215, a wave length of 2 pixels would vary approximately from 26 to 27. Because the display must be done with 256 values (28) instead of 65536 (216), altitude values must be divided by 256 before displaying them.  High frequencies fall this way to 0 and are not displayable.

I see all the messages and the dialogs text in some annoying pseudo-English, written in capitals. What's happening?
Please download the latest version, this problem has been solved in version 0.21.

I installed Geomorph 0.2x or 0.3x after uninstalling Geomorph 0.1x, and the desktop icon is gone, though the shortcut is still present. What can I do?
The directory of this icon changed between v.0.1x and 0.2x. You can now find it at  /usr/local/share/geomorph/GeoMorph.xpm. Modify the shorcut properties so that the icon field refers to this address.


Geomorph is slow! The pencil and the scale widgets are difficult to move. What can be done?

Geomorph is slow when the edited images are too large for the CPU power.

Generally, there would be a slowdown when the linear size of the image is approximately equal to the CPU speed in Mhz. So, editing a 2048x2048 could be sometimes annoying on a 2Ghz CPU. This is a very rough rule of thumb: a 2048x2048 image is 4 times bigger than a 1024x1024 image, but a 2Ghz CPU is probably more than twice as powerful as a 1Ghz one, because doubling the CPU speed usually represents a one generation step.

Version 0.30 introduces some strategies which make easier the edition of huge images. For instance, when the cursor of some scales is moved, the preview is refreshed only when the mouse button is released. Buttons have also been added beside or under scales for moving the cursor by predefined steps . Surely, some dialogs could still be improved. Please contact if you have requirements or suggestions.

Finally, it is not recommended to use Geomorph on a network, in the sense that the program is executed on computer A when it is displayed on computer B by X Windows.

I get a message telling that there is no more memory to create a new document. What should I do?
First of all, save all your documents!

At least, two reasons can explain this:
  1. Too many documents are open for the physical memory of your computer. Geomorph can work on a 256 Mb machine. However, this could be insufficient if, for instance, you increase the undo/redo stack from 5 to 10 levels or more and create a too many documents. In this case, closing some documents would free memory, but restarting Geomorph is a better solution.

  2. The hardware acceleration (direct rendering) of your video card is activated. On most tested systems a few years ago (~2005-2006), this lead to an abnormal memory usage. From version 0.31, you can unactivate the direct rendering for Geomorph only, without unactivating it for your whole system, before restarting the program. See this question.
With the exception of the memory problem related to hardware acceleration, which does not depend on Geomorph, version 0.31 has a memory leak of roughly 250 k for each open and closed document.

What should be the normal memory usage of Geomorph?

Depending on if the video card hardware acceleration is active or not, and if it is active for Geomorph or for other X-Windows applications only, the menu bar display plus one 512x512 document may require from 20 to 50 MB.

When the hardware acceleration is not active, each new 512x512 document requires some 2 MB, or 10 MB when the 5 levels of the undo / redo history are filled up.

Otherwise, the usage varies depending on the distribution and the video card driver. Each new document can require between 10 MB and 30 MB (history empty), and the memory is only partially freed when closing a document. It is always freed when leaving Geomorph, though.

Geomorph stops with an error when I try to open a new document, after having closed all the documents. What can be done?

Try to unactivate the direct rendering for Geomorph. You need version 0.31 or later for this. See this question.

Why does Geomorph crash when I try to clone a document?

This happened when cloning a new document, still unsaved, before version 0.31. Now Geomorph asks to save the document before cloning it.


When I click on the render icon
, nothing happens. What can I do?

The following explanations work for POV-Ray 3.6.

First of all, start Geomorph from a console, so that you see the POV-Ray messages.

If POV-Ray does not start at all, read the next question. Geomorph would probably freeze.

If POV-Ray starts but displays no image, there should be an error message in the verbose output.

If the message says something about a missing "povray.conf" file, check if your have such a file in your /home/.../.povray/3.6 directory. This file appeared with version 3.6 for controlling some security features. If it is absent, create it:
If the message is not related to povray.conf, maybe you made a mistake when editing the POV-Ray script?

If you feel desperate, copy and paste me the console output in an e-mail, I'll see what I can do.

Why does Geomorph freeze when I click on the render icon ?

Geomorph does not find the POV-Ray program, because POV-Ray is not installed or because the name of the program is not written correctly in the options file ~/geomorph/geomorphrc.

Check the Renderer variable in ~/geomorph/geomorphrc , or check it in the "Renderer" tab of the options dialog in the menu bar . If you want to check if the program exists, type "which <name>" in a console (ex. "which povray36").

When Geomorph is frozen, you must kill the process with xkill or kill -9 <pid> in a console.

The Povray output disappears as soon as it is done. What can I do?

The "Pause" option must be added when launching POV-Ray. This can be done in one of three ways :
  1. Go in the options dialog of the menu bar and add the +P option in the variable "Other command line rendering options" in the "Renderer" tab.
  1. Modify the variable other_render_options directly in the ~/geomorph/geomorphrc file:
other_render_options = +P +D -F +L/home/.../geomorph;

  1. Insert the line Pause_when_Done = on in the ~/.povrayrc file, if you have one. You can copy a template of this file from /usr/lib/povray-3.6/ini/povray.ini.

Why doesn't Geomorph interface with other renderers than POV-Ray, for instance Aqsis or YafRay?

The Aqsis and YafRay renderers are free like in "freedom", covered by the GPL for the first, by the LGPL for the second, unlike the current version of POV-Ray (3.6).

Why didn't I choose a free renderer to interface with Geomorph? At the beginning, POV-Ray was the sole renderer I knew. I don't mind about interfacing Geomorph with other renderers. It's mainly a matter of knowledge, of time to learn how to use the other renderers and of work to develop the interface functions. I think that these renderers don't process height maps natively, the images should be converted to meshes before. This could be resource-intensive, but it is feasible. A matter of contribution for the courageous!

Last revisions November the 25th, 2005, January the 27th, 2007, and August the 1st, 2008

Contact:    Patrice St-Gelais