Electro, Blender, twaka, cavevars

(more detail will be added to this page or the course wiki as the course continues)

Current Issues ...

- there is an electro users group at google: http://groups.google.com/group/electro-users

Working with Electro

The main information resource for electro is http://www.evl.uic.edu/rlk/electro/ You should grab the current version of electro for your platform of choice. Most likely you will want to recompile from the latest subversion source. Note that if you want to build electro yourself you will need to grab a bunch of libraries it depends on. This is pretty straight-forward but with ODE you need to build with enable-release so it doesn't keep giving warnings.

I have created a small program in electro to give you a starting point for your work. It lives in sample.tar.gz

This code sets up a simple world that shows off various things you can do with electro.



The application runs in with stereo visuals on the C-Wall. You can navigate around the scene with the wand and change your perspective by walking or moving your head.

You can see a representation of your hand where the wand is located. The left wand button causes a new crate to drop. When touching the fountain you can use the middle wand button to turn the fountain on and off.  That same middle button can be used to pick up and throw a crate. The right wand button shoots out a ball. You can also use the wand to push the crates over.

The fountain gives off directional sound when its on and there are sounds when a new crate or ball is created with the wand.

To run the simple world on a linux / OS-X laptop/desktop computer:
1. go to the twaka/linux-mac directory in simple.tar.gz, edit the makefile, and make to create the twaka executable
2. start twaka. You should see a window pop up with the twaka keyboard commands. There is more info on twaka below.
3. copy your electro executable into the simple directory (not necessary but convenient)
4. in another terminal window go to the simple directory and electro simulator.lua simple.lua
5. give the twaka window focus and use the keyboard to interact with the electro window
6. escape quits electro, and q quits twaka


To run the simple world on a windows laptop/desktop computer:
0. you should be able to double-click the twaka.exe executable in the twaka/windows directory of sample.tar.gz otherwise there is a visual studio 6 workspace to build it. You will likely need to tweak some things to get it to work in .net. When twaka runs you should see a window pop up with the twaka keyboard commands. There is more info on twaka below.
1. copy simulator.lua from the simple directory to electro-10XX/config
2. edit electro.bat file so that it looks like this:
  rem -----------------------------------------------------------------------
  rem This batch file acts as a drag-and-drop target for Electro Lua scripts.

  %~d1
  cd "%~dp1"
  rem"%~dp0electro.exe" -f %1

  rem -----------------------------------------------------------------------
  rem Configure with a default display config as follows:
  rem
 "%~dp0electro.exe" -f "%~dp0\config\simulator.lua" -f %1

3. drag and drop simple.lua onto the electro.bat file
4. give the twaka window focus and use the keyboard to interact with the electro window
5. escape quits electro, and q quits twaka

To run the simple world on the C-Wall computer:
1. make sure the tracker is working with /usr/local/CAVE/bin/cavevars - if not see the cavevars section at the bottom if this pate
2. in one terminal window ~aej/GOTRACKER will take tracking data and place it into shared memory on the C-Wall machine. You should see the numbers changing slightly
3. by default the simple code is set up for monoscopic viewing so for stereo you need to uncomment the line
  E.set_camera_stereo(camera, E.stereo_mode_tile, -EYESEP, 0, 0, EYESEP, 0, 0)
4. in another terminal window go to your simple directory ~aej/electro/electro cwall.lua simple.lua
5. escape quits electro
Blender

You can use any modelling package you prefer as long as it can produce a .obj file for Electro to read in. Blender has been popular lately. Personally I like ac3d, which is less powerful but has a more 'normal' interface than blender. One thing to note is that Electro can not deal with scaled textures.

http://www.blender.org/

There is a good tutorial here: http://www.idevgames.com/index.php/news/comments/blender_basics_free_classroom_tutorial_book/

twaka

VR programming can be tricky because interaction in a VR environment is very different from interaction on a typical computer, and VR environements need to be experienced at 1:1 scale, so its best to test the application in the VR environment where it will be deployed. Unfortunately that's not very convenient, so most development will likely take place on a laptop or desktop pc, but at regular intervals you should test on the actual C-Wall hardware.

To make development a bit easier I have written some tracker simulation code called twaka that allows you to use the keyboard to simulate moving around, turning, using the wand. This application runs separately from your electro application on the same computer and feeds appropriate values into shared memory for the electro application to read. twaka runs in OS-X (10.4.10 for sure) , linux (SUSE 10.2 for sure), and windows (XP sp2 for sure)

cavevars

An important program on the C-Wall is /usr/local/CAVE/bin/cavevars

It is a simple application that displays the current state of the C-Wall so you can check that the tracker is working, the wand is working, and that the projectors are showing the correct eye view. Before doing any work on the C-Wall its worth taking a couple minutes to run cavevars and make sure everything is OK.

If things are not OK, for example if you move the glasses or the wand and the tracker values do not update, then you may need to restart the tracker. You should shut down the laptop running the tracker, then turn off the tracking system, wait a few seconds, turn on the tracker, then turn on the laptop.

Note that if you are only seeing scenery in your left eye and the sky in the right eye then you need to set your electro code to run in stereo. In simple.lua you would uncomment the line:
  E.set_camera_stereo(camera, E.stereo_mode_tile, -EYESEP, 0, 0, EYESEP, 0, 0)

last revision 8/20/07