My technical notes ...

Segment 3D model in blender to get a separate OBJ goup

2011-01-06T16:02:00.000-08:00



Procedure:
  
1) Laso select desired faces in edit mode - CTL+LMS drag (use vertex/edge/face selection as needed - buttons at the right end). First select roughly and unlselect (CTR+Shift+LMS drag) to refine the selection. Edge mode helps here.

2) Split by pressing 'p' (split P mesh/vertex/split)

3) Select the part in object mode (tab) and give object and data block name in Link and Materials window.

4) Select all and export as obj (Say export blender objects as OBJ groups using the buttons at the bottom)


Refs:

http://wiki.blender.org/index.php/Doc:Manual/Modeling/Objects/Groups_and_Parenting
http://wiki.blender.org/index.php/Doc:Manual/Modeling/Meshes/Selection

Emacs as an IDE

2010-11-30T02:53:00.001-08:00

http://deep.syminet.com/emacside.html

Fast rendering 2D projections of 3D model data

2010-04-07T00:32:00.000-07:00

The renderer performs a high speed rendering of a Autodesk 3DS model, using OpenGL offscreen rendering. The rendered image could be pixel intensities, surface normal values or other attributes.

Given a 3DS model like this:

For a given rotation, shift and scale, a 2D projection like this is rendered. Intensity values are returned/stored in memory for further processing.

Alternatively, other attributes like surface normal components could also be rendered instead of the color intensities.

For example x, y, z components of the model surface normals have been rendered in the 3 images below.

Misaligned 3ds model rendered with model3d

2010-03-22T21:26:00.001-07:00

shell script to rename all UPPERCASE files to lowercase

2010-03-16T17:39:00.000-07:00

for f in *; do
g=`expr "xxx$f" : 'xxx$.*$' | tr '[A-Z]' '[a-z]'`
mv "$f" "$g"
done

Notes on compiling mex file without gcc version warning

2010-03-09T15:27:00.001-08:00

http://www.mathworks.com/access/helpdesk_r13/help/techdoc/matlab_prog/ch7_pe30.html#784594

Changed mexopts.sh as (Matlab2009b/bim/mexopts.sh is changed use mex -setup to select that conf as the default after the changes)

glnx86)
#----------------------------------------------------------------------------
RPATH="-Wl,-rpath-link,$TMW_ROOT/bin/$Arch"
# StorageVersion: 1.0
# CkeyName: GNU C
# CkeyManufacturer: GNU
# CkeyLanguage: C
# CkeyVersion:

#CC='gcc'
CC='gcc-4.1'

#CFLAGS='-ansi -D_GNU_SOURCE'
#Srimal: we allow // style comments due to opencv .h files
CFLAGS='-D_GNU_SOURCE'

Run mex functions using opencv 2.0 code with MATLAB R2009b

2010-03-05T00:55:00.001-08:00

We get this error:

??? Invalid MEX-file '/home/srimal/svnworking/renderer/mexLossC/mexLossC.mexglx':
/home/srimal/MatlabR2009b/bin/glnx86/../../sys/os/glnx86/libstdc++.so.6: version `GLIBCXX_3.4.11' not found (required by
/usr/local/lib/libcvaux.so.4).

Solution:

~/MatlabR2009b/sys/os/glnx86
ln -s /usr/lib/libstdc++.so.6.0.13 ~/MatlabR2009b/sys/os/glnx86/libstdc++.so.6

Allow C // style comments in MATLAB mex functions

2010-03-05T00:38:00.000-08:00

Remove the -ansi CFLAG

Change

CFLAGS='-ansi -D_GNU_SOURCE'

to

CFLAGS='-D_GNU_SOURCE'

in MatlabR2009b/bin/mexopts.sh

and use

mex -setup to select this conf.

OpenCV 2.00 with eclipse

2010-03-04T23:44:00.000-08:00

To get the compile options,

$ pkg-config opencv --cflags --libs
-I/usr/local/include/opencv -L/usr/local/lib -lcv -lhighgui -lcvaux -lml -lcxcore

Include the above in eclipse project properties.

Compiling programs that use GSL

2010-03-02T22:43:00.001-08:00

GCC:
$ gcc myprogram.c `pkg-config --cflags --libs gsl` -o myprogram

Eclipse:
add compiler / linker settings (alt+enter) to match (individually -I -L -l ...fileds)
$ pkg-config --cflags --libs gsl
-I/usr/local/include -L/usr/local/lib -lgsl -lgslcblas -lm

Eclipse and SVN (dont use eclipse tools - use cmdline svn)

2010-03-02T19:56:00.001-08:00

1 All eclipse svn methods failed and/or too messy
2 manually svn ci into some dir (~/svnworking)
3 create new eclipse workspace ~/eclipse_workspace_svnworking
4 switch to that
5 in eclipse Import> General > Existing project into workspace (select dir from ~/svnworking which was previously checked out manually using svn)
6 this will change the code in ~/eclipse_workspace_svnworking directly
7 svn ci as usual from a terminal

Eclipse C / OpenGL tips

2009-12-09T20:14:00.000-08:00

Importing existing C Makefile projects
Create New Project > C Project > Makefile project

To Debug using eclipse add to CFLAGS in Makefile
-g -O0

OpenGL and Eclipse Debug(gdb?) works
http://www.eclipse.org/downloads/download.php?file=/technology/epp/downloads/release/galileo/SR1/eclipse-cpp-galileo-SR1-linux-gtk.tar.gz&url=http://download.eclipse.org/technology/epp/downloads/release/galileo/SR1/eclipse-cpp-galileo-SR1-linux-gtk.tar.gz&mirror_id=1

OpenGL Superbible (3edn) and code
http://proquest.safaribooksonline.com/0672326019/ch01?reader=html#X2ludGVybmFsX0ZsYXNoUmVhZGVyP3htbGlkPTA2NzIzMjYwMTkvY2gxNWxldjJzZWMxMiZpbWFnZXBhZ2U9

Blender Aim the Cam

2009-10-21T23:37:00.001-07:00

To make one or more objects track another object (the target) select at least two objects and press CtrlT. The active object becomes the target and the others objects the trackers. The (Make Track Menu) provides several options for creating the initial tracking:

http://wiki.blender.org/index.php/Doc:Manual/Modelling/Objects/Tracking

Read vertex cordinates in Blender3D

2009-10-06T00:36:00.000-07:00

Blender can be used to read the coordinates of a desired vertex off a 3D model (Ex: 3ds)

1) Zoom in to the desired area (scroll button = zoom, middle drag = rotate, shift+middle = pan)
2) 'Tab' to enter 'edit' mode
3) Right click desired vertex
4) 'n' to see vertex coordinates

3D to 2D Rendering, OpenGL and MATLAB

2009-09-06T23:03:00.000-07:00

Short notes on OpenGL rendering and attempted integration with MATLAB.

Vertex Buffer Objects (VBO)

Allows you to give vertex, vertexnoms, face array locations directly for openGL to render (as opposed to drawing triangles one by one)

Frame Buffer Objects (FBO)

Allows you to draw to a buffer/texture (without directly to the screen)

Ref: http://hacksoflife.blogspot.com/2006/10/vbos-pbos-and-fbos.html

MEX and OpenGL

Use mex -v -lGL -lglut -lGLU cfile.c
Problems with glutinit() when calling mex file (MATLAB crashes when mex file is caleld again - cant do repeated rendering/calculations)
Probably not possible?
http://www.mathworks.com/matlabcentral/newsreader/view_thread/166039
http://mathforum.org/kb/message.jspa?messageID=6145127&tstart=15

Multi hop ssh tunnelling

2009-08-27T03:44:00.001-07:00

localhost ----linkA----> gatewayhost ----linkB-----> remotehost

localport <========ssh============>remoteport

Requirement:

Need to access remote service in remotehost (on remoteport) from localport in localhost (this quite be a database service to anhttp proxy service -- not much difference here)
Both links A and B allow only SSH traffic (other ports are blocked)

Solution 1:

A simple

$ ssh -L localport:remotehost:remortport -N -f remoteuser@remotehost

would create an ssh tunnel on link A but not on link B . As both links allow only ssh traffic this will not work.

One solution is to use the ssh proxycommand option like this:

$ ssh -oproxycommand="ssh -qaxT gwuser@gatewayhost nc %h %p" -L 3128:localhost:9998 -p9999 remoteuser@remotehost -N -f

Publickey (no password) ssh/scp in Ubuntu (9.04 and maybe other)

2009-08-17T21:08:00.000-07:00

As per launchpad

https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/201786

There is a bug that prevents public key ssh/scp from working when configured according to 'man ssh'. (Due to the way ssh-agent / seahorse is setup )

The trick is to run 'ssh-add' after the normal procedure as per 'man ssh'.

So the entire procedure would be something like this.

Generate keys on the local machine ($ ssh-keygen -t rsa -b 4096 #press enter twice, I'm using 4096 instead of the usual 2048 bit key)
Copy the public key using ssh-copy ($ ssh-copy-id -i ~/.ssh/id_rsa.pub remoteuser@remotehost #assuming keys are in the standard location)
Now make sure we run ssh-add ($ ssh-add )

That should do the trick!

Skype on Ubuntu 9.04 with mic and headset problems

2009-07-17T01:03:00.000-07:00

This was tested on Ubuntu 9.04 running on a Dell OptiPlex 960.

A simple handset was used with the mic and earphone jacks connected to the sockets in the front (above the USB slots).

A picture speaks a thousand words.. so its all in the screenshots.

Step 1: Change volumes settings as follows.

Step 2: Change skype options as follows

This might also help:
http://funwithlinux.wordpress.com/2009/04/20/fixing-skype-audio-problem-on-ubuntu-904/#comment-50

NoixACL

2009-03-31T22:53:00.001-07:00

My Screenshot 1

Web services for ISO8583 Messaging using MultiXTpm ISO 8583 Server

2009-03-06T01:09:00.000-08:00

MultiXTpm ISO 8583 Server exposes a web service to receive ISO8583 messages.

ISO 8583 Messages are used for financial transaction messaging including Credit Card / POS transaction messages.

MultiXTpm ISO 8583 Server comes bundled with the MultiXTpm Application Server developed by Moshe Shitrit, who is also extremely helpful by the way :).

This document explains how to deploy MultiXTpm ISO 8583 Server (and in effect MultiXTpmApplicationServer-4.0.8a) on a Ubuntu 8.04. It is intended to be quick guide for newbies as well as a reference for me as I may not remember these steps next week !

1) First Install MultiXTpmApplicationServer

The basic installation was done by following Igor Custodio's excellent posting on A How-to compile MultiXTpm in Ubuntu 8.04.

However, the following modifications had to be done in addition to the instructions given in A How-to compile MultiXTpm in Ubuntu 8.04.

The LD_LIBRARY_PATH and PATH variables needed to include the current directory (.) to run the mentioned .sh scripts. Therefore the export statements in Step 6, were modified as follows.

export MultiXTpm="/home/srimal/MXTPM/MultiXTpmApplicationServer"
export PATH=.:$PATH:"${MultiXTpm}"/runtime
export TMAKEPATH="/usr/share/tmake/linux-g++/"
export LD_LIBRARY_PATH=.:"${LD_LIBRARY_PATH}":"${MultiXTpm}"/runtime
export CPATH="/home/srimalj/MXTPM/gsoap-2.7/gsoap:/home/srimalj/MXTPM/gsoap-2.7/gsoap/extras"
export CPLUS_INCLUDE_PATH=/usr/include/mysql++/:/usr/include/mysql/

These exports were added to the end of my /etc/bash.bashrc for convenience.
(I have installed in my home directory /home/srimal -- change as appropriate)

Also install the following packages if you already don't have them.

$ sudo apt-get install libmysql++-dev

Plus any other libraries that you do not have already but are mentioned in the above export statements. (Hint: Missing header files are usually in xxx-dev package for package xxx)

2) Next Install MultiXTpm ISO 8583 Server

To do this, change in to the ISO8583Server directory .

$ cd ${MultiXTpm}/ISO8583Server

The next few steps require the environment variables exported before. (Its a good idea to add it to /etc/bash.bashrc and start with a new terminal -- or do a . /etc/bash.bashrc if you prefer to use the same terminal window)

Next we Build everything.

$ ./LinuxBuildAll.sh

Then Make the runtime environment.

$./MakeRuntime.sh
(Don't worry if it says the runtime exists)

Now change to the runtime directory

$ cd runtime

and run MultiXTpm

$ MultiXTpm

This should start up the MultiXTpm process which will in turn spawn the four processes needed for ISO 8583 Server:

MultiXTpm – Application Server, Router, load balancer.
ISO 8583 Issuer Gateway FE – Listener and communications handler, receivng requests from Remote Acquirer Gateways or POS terminal.
ISO 8583 Issuer Gateway WS FE – Listener and communications handler, receivng requests from Remote Acquirer Gateways or POS terminal that use SOAP/XML Web Services client software.
ISO 8583 Back End and/or ISO 8583 Authorizer – The Business Logic handler. Acts locally on POS terminals requests or forwards requests to the next Issuer Gateway in the chain.
ISO 8583 Acquirer Gateway FE – Connection initiator and communications handler. Handles all data transfers to remote Issuer Gateways.

This is what my console looks like.

Based on the default TpmConfig.xml the Web Service will be accepting connections on port 38583. So my connection end point looks like "http://localhost:38583/" .

GUI Database Designer for MySQL

2009-02-19T00:12:00.000-08:00

MySQL Workbench

http://dev.mysql.com/downloads/gui-tools/5.0.html

has Linux support

and generates lovely ERD's off MySQL schemas :)

Blue Tooth Remote Presenter on Ubuntu 8.04

2009-02-18T23:33:00.001-08:00

Install these

sudo apt-get install bluez-utils

Scan for the phone,

hcitool scan

We see something like

00:11:22:AA:BB:CC  w810-Srimal

Connect like this,

sudo hidd --connect 00:11:22:AA:BB:CC

Use the phone ;)

Grails - Acegi -- Set After Logout page

2008-11-10T02:10:00.000-08:00

Crate a new action with the following code:

import javax.servlet.http.HttpSession

class LogoutController {

...

action {
HttpSession s = request.getSession()
s.invalidate()
redirect(controller:"itemPrice", action:"listDOA") // this is the new after
}
}

How to restore Grub from a live Ubuntu cd.

2008-11-05T00:44:00.000-08:00

How to restore Grub from a live Ubuntu cd.

This will restore grub if you already had grub installed but lost it to a windows install or some other occurence that erased/changed your MBR so that grub no longer appears at start up or it returns an error.

(This how to is written for Ubuntu but should work on other systems. The only thing to take note of, when you see "sudo" that will mean to you that the following command should be entered at a root terminal.)

Boot into the live Ubuntu cd. This can be the live installer cd or the older live session Ubuntu cds.

When you get to the desktop open a terminal and enter. (I am going to give you the commands and then I will explain them later)

Code:

sudo grub

This will get you a "grub>" prompt (i.e. the grub shell). At grub>. enter these commands

Code:

find /boot/grub/stage1

This will return a location. If you have more than one, select the installation that you want to provide the grub files.
Next, THIS IS IMPORTANT, whatever was returned for the find command use it in the next line (you are still at grub>. when you enter the next 3 commands)

Code:

root (hd?,?)

Again use the value from the find command i.e. if find returned (hd0,1) then you would enter root (hd0,1)

Next enter the command to install grub to the mbr

Code:

setup (hd0)

Finally exit the grub shell

Code:

quit

That is it. Grub will be installed to the mbr.
When you reboot, you will have the grub menu at startup.

Reference
http://ubuntuforums.org/showthread.php?t=224351

Grails/Groovy refs:

2008-10-07T22:46:00.000-07:00

http://groovy.codehaus.org
http://codehaus.org

Using the Mic with Skype 2 on Ubuntu 8

2008-05-23T10:18:00.000-07:00

1. Open volume control (dbl click on the icon or type gnome-volume-control in a terminal)

2. Go to 'Preferences' and enable the 'Capture' device.

3. Adjust the volume for the 'capture' device and make sure its not in mute.

4. That worked for me :)

How to change resolution in Gnome without the panel icons jumping around

2008-05-13T03:48:00.001-07:00

The gnome panel has this annoying habit of letting loose of your panel icons when you change the screen resolution. (This happens when I step down the screen resolution to suite the projector, for example).

To prevent this, a nifty little application called 'pessulus' can be used to lock down the panels.

It can be installed in ubuntu as follows.


$ sudo apt-get install 'pessulus'

$ pessulus

Lock down the panel as shown in the screenshot below.

No more messing up the panel icons when changing the screen resolution :)

Encrypted chats with Pidgin / Gaim

2008-05-06T00:36:00.000-07:00

Doing encrypted (RSA) chats using pidgin is as simple as:

$ sudo apt-get install pidgin-encryption

This installs the encryption plugin.

Encrypted chats are possible once you enable this plugin from preferences in pidgin.

Note the 'padlock sign' in the chat window below.

Check the packet data for yourself using a packet analyser like 'wireshark'.

Its encrypted !

:)

Installing Epson Perfection 660 USB Scanner in Ubuntu 7.10/8.04

2008-04-20T09:22:00.000-07:00

Unfortunately Ubuntu did not autodetect my scanner but the installation was trivial.

Obtained the driver file from http://www.epson.com.sg/epson/drivers/driver_download.htm?dc=1&mode=3&m=false&catid=5&pid=46
Unzip the file. The file we need is TAIL_061.BIN (which is inside /DATA/BIN inside the zip file). Put this file in /usr/share/sane (or anywhere you please) and give read permission to all (chmod a+r /usr/share/sane/TAIL_061.BIN as root)

Edit /etc/sane.d/snapscan.conf and change following line. (do as root)

 firmware /usr/share/sane/snapscan/your-firmwarefilefirmware

  to

firmware /usr/share/sane/TAIL_061.BIN.bin

Plug the USB cable
Start xsane (type xsane in a terminal or find the program from the menu)
Thats it!

Local DNS cache to speed up Ubuntu/Debian

2008-04-04T10:58:00.001-07:00

This article explains how to setup dnsmasq to speed up dns requests.

http://ubuntu.wordpress.com/2006/08/02/local-dns-cache-for-faster-browsing/