New blog – Old blog…

This blog has moved to my personal site: http://blog.nielshorn.net. Please update your bookmarks!

All existing posts have been imported into the new blog and the old copies will stay here to guarantee that older links continue to function.

Since the update of all DNS servers on the internet may take up to 24 hours, please try again later if the link does not work yet.

2010...

2009 is gone, 2010 has started.

Lots of sad news here in Rio, after all the rain that has fallen here over the last few days, but life goes on :(

In just a few days I will officially be on vacation, so I might not have too much time to write here, but I still have some raw material I want to publish, like some experiences with nagios (working very fine here), ntop, cacti, zabbix, etc.

And I'm working on some lay-out changes for my blog, so be prepared to see some novelties here :)

Happy New Year!

Using a 32-bits program in a 64-bits Linux environment

When Slackware released its first test version of Slackware64, I installed it on a separate partition to try it out. I was immediately impressed by the performance boost of some programs, especially some graphic programs I use.

Since I compile most programs that are not available on a standard Slackware installation from source, I didn't have too much trouble switching completely from 32-bits to 64-bits when the official release came out.
But for some programs the source code is not available. The original author / site may have disappeared, or it might simply be "closed" software.
I had this problem with some older programs I still used and they simply would not run on Slackware64. The error they normally return is:

<program_name>: No such file or directory

This error actually means that the binary file is looking for some (32-bits) library it cannot find, simply because they do not exist on pure 64-bits Linux installations.

One option was to go "multi-lib" - install the 32-bits libraries on my Slackware64 box. But I did not want to go that way, as I preferred to keep my installation as "pure" as possible.

So I started looking for another solution, and on the LinuxQuestions.org forum someone pointed me to statifier.

Statifier simply combines the binary executable with all the libraries it needs into one (big!) executable "semi-static" file. I won't go into the details how it does that (because I also do not understand all the details...), so if you want to know more, check out the site of the author.

The only problem is that you will need a 32-bits machine where your binary works fine, to "statify" it. I still had my 32-bits Slackware partition, so no problem for me here.

Statifier is open source software, so you can build it yourself, or get my package for Slackware on my site.

After installing or building Statifier on your 32-bits machine, you can use it to "statify" your 32-bits binary like this:

$ statifier <binary> <new_binary>

Remember that the result will be a lot bigger than the original, as it includes all the libraries that are normally loaded dynamically. As an example, I used it on "l3p", a small program to convert LDraw files to POV-Ray files, only available in a 32-bits version.
The original file was 140K, the statified version is 2.7M :)
But it solved my problem and I can use l3p on my 64-bits Slackware64 installation!

If you want to use l3p on Slackware64 as well but this is all too technical for you, you can get the statified version of l3p as a Slackware package from my site.

"lgeo" Slackware package available

After some requests, I created a Slackware package with the lgeo parts library. It can be downloaded from my site.

If you prefer, you can download the library from the author's website and use the SlackBuild to create your own package.

Updated LDraw_data package available

I created an updated package with the LDRAW Library of Lego pieces that includes all parts up to September, 16th, 2009.

The "unix-complete" file from ldraw.org has not been updated for years, so this package was based on the Windows file "complete.zip" but can be used without any problems under Slackware.

As always, the package can be downloaded from my site.

Lego & POV-Ray on Linux

Some time ago I promised to give some basic instructions on how to create nice images of Lego constructions with POV-Ray on Linux. Now that Christmas is arriving, I finally found some time to convert my own instructions into something that can almost be called a "tutorial" :)

What will you need:

1. LeoCAD - to "build" your constrution


2. (optional) a viewer program, like LDView or ldglite


3. l3p - to convert the .ldr (LDRaw) file to .pov (POV-Ray)


4. (optional) The "lgeo" parts collection


5. POV-Ray - the "Ray-Tracer program"

If you use Slackware, you can find packages for all of these on my site and SlackBuilds for all except 3 on www.slackbuilds.org. For many other Linux distributions packages are available in their repositories.

First step - Build something!

If you do not have any LDraw file yet with a Lego creation, then now is the time to make one.
As an example for this tutorial, I built a little penguin, based on the instructions here, with LeoCAD:


Save your creation with LeoCAD as a ".ldr" file ("File" - "Save as" from the menu). The resulting file in my case was:

0 Model exported from LeoCAD
0 Original name: Penguin.lcd

 1 14 -50.00 -0.00 -60.00 -0.00 0.00 1.00 -0.00 1.00 -0.00 -1.00 -0.00 -0.00 3002.DAT
 1 15 -50.00 -24.00 -60.00 -1.00 0.00 -0.00 0.00 1.00 -0.00 0.00 -0.00 -1.00 3004.DAT
 1 15 -50.00 -48.00 -60.00 -1.00 0.00 -0.00 0.00 1.00 -0.00 0.00 -0.00 -1.00 3004.DAT
 1 0 -50.00 -24.00 -40.00 -1.00 0.00 -0.00 0.00 1.00 -0.00 0.00 -0.00 -1.00 3004.DAT
 1 0 -70.00 -48.00 -40.00 -1.00 0.00 -0.00 0.00 1.00 -0.00 0.00 -0.00 -1.00 3004.DAT
 1 0 -30.00 -48.00 -40.00 -1.00 0.00 -0.00 0.00 1.00 -0.00 0.00 -0.00 -1.00 3004.DAT
 1 0 -50.00 -72.00 -40.00 -1.00 0.00 -0.00 0.00 1.00 -0.00 0.00 -0.00 -1.00 3004.DAT
 1 14 -50.00 -72.00 -70.00 -1.00 0.00 -0.00 0.00 1.00 -0.00 0.00 -0.00 -1.00 3003.DAT
 1 0 -50.00 -96.00 -50.00 -1.00 0.00 -0.00 0.00 1.00 -0.00 0.00 -0.00 -1.00 3003.DAT
0

Second step - View your model with ldglite or LDView

This step can be skipped, but it is a nice test to check if the programs can find all the LDRAW parts on your computer. LeoCAD uses its own parts library, so being able to view it there does not necessarily mean that the LDRAW library is accessible.

This is how the penguin looks like in ldglite, a simple but very fast program to visualize your creations:


A second option is to use LDView, a very nice and very complete program to visualize your creations. It creates a more realistic view of the model, with some shading effects:



Third step - Ray-Tracing

So the images created by LDView are nice. But we want something even better! Enter POV-Ray, a very professional Ray-Tracing program that is completely free.
It "traces" light-rays, by tracing paths of "light particles" from one or more light sources, bouncing off surfaces and reflecting into the lens of a camera.

So we define the position and colors of the light sources, the position and angle of the camera, the types of surfaces (smooth, reflective, rough, etc.), etc.

Sounds complicated? Well, there is a very nice utility called l3p that tries to do most if it automatically to help us get started. l3p reads an "ldr" file, guesses the best position and angle for the camera so that the whole creation will fit in the image, and sets up three light sources around the model. Then it creates a .pov file that can be read by POV-Ray.

l3p needs to know where the LDRAW library is stored on your computer. This can be set by the LDRAWDIR environment variable like:

$ export LDRAWDIR=/usr/share/LDRAW

Put this in your start-up script like ~/.bash_profile (if you use bash for a shell).

Enough theory, let's create our first .pov file:

$ l3p -o Penguin.ldr

This reads the "Penguin.ldr" file we created and writes a "Penguin.pov" file in the current directory.
I used just one option - "-o" - which instructs l3p to overwrite Penguin.pov if it already exists, since we'll perform various tests before we get the final result.

Now let's run POV-Ray to transform the .pov file into an image:

$ povray +OPenguin.png +FN +P Penguin.pov

The options here mean:

• +OPenguin.png - Output will be Penguin.png


• +FN - Format will be a PNG file


• +P - Pause after creating the image, showing the result on the screen

The result should look like this:


For a first test, it's just about "OK"... But we can do better than this!

Since in most tests we'll run l3p and povray as a sequence, we'll put both commands on one line like this:

$ l3p <options> && povray <options>

The "&&" means that the next command is only executed if the previous terminated without error.

So let's try:

$ l3p -b -o Penguin.ldr && povray +OPenguin.png +FN +W640 +H480 +P Penguin.pov

What did we add:

• -b - add a standard blue background to replace the black void


• +W640 - Create the image with a width of 640 pixels instead of the standard 320


• +H480 - and a height of 480 pixels instead of 240

The result should look like this:


Let's improve the image a bit more:

$ l3p -b -q4 -bu -o Penguin.ldr && povray +OPenguin.png +FN +W640 +H480 +A +P Penguin.pov

The new options are:

• -q4 - Quality level 4, this includes the "Lego" name on the studs


• -bu - Create "bumps", this makes the surfaces more "uneven", or more realistic


• +A - Anti-aliasing, this prevents those "jagged edges"

This should be the result:



Advanced options

As I wrote in the beginning, l3p automatically guesses the best position and angle for the camera and light sources. But we can change them as we please.
Let's try something:

$ l3p -b -q4 -bu -cg40,45 -cpct10 -f -o Penguin.ldr && povray +OPenguin.png +FN +W640 +H480 +A +P Penguin.pov

I included two new options:

• -cg40,45 - Put the camera at "globe" positions 40° latitude and 45° longitude (the default is 30,45 so we put it a bit "higher")


• -cpct10 - move the camera back 10%, so that the object is not so close to the edges of the image


• -f - put a "floor" under the penguin instead of letting it float in the sky, so that we can see the shadows of the light sources

Here is the result:


You can play around with the position of the light sources using the "-lg" option. I'll leave this as an exercise! :)

There are many more advanced options to try. Type "l3p" without any options to see the complete list! If you have a good tip, feel free to post a comment so that I can learn something new.

Using the lgeo library

The images we created with the standard l3p + povray combination look quite good, but when we enlarge the images, the pieces look a bit unrealistic, with edges that are too sharp, etc.

Enter the "lgeo" library of pieces...

The lgeo pieces are specially designed for use with POV-Ray, with more realistic edges, surfaces, etc. l3p can automatically replace all LDRAW pieces with lgeo pieces if a substitute is available (any many are available, at least for the more "standard" pieces).

We just need to include the "-lgeo" parameter (and have the lgeo library installed and "readable" by povray - this needs some configuration...).
This created a nice image of our Penguin at a larger size:

$ l3p -b -q4 -bu -cg40,45 -cpct10 -f -lgeo -o Penguin.ldr && povray +OPenguin.png +FN +W1280 +H960 +A +P Penguin.pov

And this is the result (click on the image to see the full-scale picture):


As you can see, the studs and the edges look more realistic in this picture.

Have fun!

LDView error "libboost_thread-mt.so"

For those who use LDView on Slackware-current and noticed that it suddenly stopped working: the problem is in the latest update of the "boost" library:

+--------------------------+
Thu Dec 17 20:51:37 UTC 2009
...
l/boost-1.41.0-x86_64-1.txz: Upgraded.

This latest update does not include the *-mt (=multi-thread) libraries, as the "normal" version is already multi-threaded.

The solution to get LDView working again is simply rebuild it from the SlackBuild:
- Download the SlackBuild script & untar it
- Download the source for LDView
- run the SlackBuild as:
   # BUILD=2 ./LDView.SlackBuild
- use upgradepkg to upgrade your LDView