[Evolveproject-design] I'm back!

[Robert S. <ro...@pr...>]

Hey guys,

I'm back from Taiwan.  I will be at our friday meeting this week.  So 
here's a short update.  Over the past two weeks I've been playing around 
with a physics engine called ODE, which stands for Open Dynamics 
Engine(http://www.ode.org/).  This project was written in C, but some 
smart folks created a JNI (Java Native Interface) called odejava 
(http://odejava.org).  The concept here is similar to that of using JOGL 
to access OpenGL libraries.  Just like JOGL, there are odejava binaries 
for windows, linux and mac.  Anyway, I actually got a running simulation 
(just physical stuff) of a bunch of 4 wheeled robots just like what 
we're modeling.  ODE is fast and stable and it will allow us to do some 
great stuff.  Right now I'm just working on the final piece of the 
puzzle, the Evolve to ODE interface and meanwhile I'm cleaning up a 
bunch of other stuff.  I created a new project called Evolve3.  I am 
confident this will become our mainline codebase within a week or two, 
I've already made significant progress.

This is the feature set I expect as a part of phase 1:

   1. Mostly continuous world.  No more rounds!!!
   2. Realistic physics.  The bugs have 4 wheels (each motor controls
      two wheels, kinda like a tank). 
   3. Movement impedance will be replaced by the concept of friction
      (I'm not 100% sure about this one, more of a try it out and see if
      it makes sense type feature.  Ridiculously simple to implement
      however.)

This is planned feature set for phase 2, subject to change depending how 
phase 1 works out:

   1. Have a concept of "Sensor Space" where sensors are represented as
      physical objects that are located somewhere on the bug chassis. 
      However instead of belonging to the same collision space that the
      bugs belong to, they will have their own sensor space.  Stimuli
      objects (like aroma clouds) will also exist in this "Sensor
      Space", so all we look for is the collision between a sensor and
      its stimuli after each step of the simulation (btw, "looking for
      collisions" just involves asking ODE to find them for you =) ). 
      These kind of operations are actually cheap in ODE, since it
      treats collisions in each space completely separately.  The real
      motivation here is not so much for the benefit of using ODE to do
      our sensing for us, but more for letting ODE transform the sensors
      physical position and orientation for us.
   2. Three Dimensions.  Technically phase 1 will be in 3 dimensions but
      the environment will still be 2D (no cliffs or peaks, just flat
      area).  I have some ideas on this might be done but i want to save
      it for after we have something working.
   3. We can replace our bresenham line calculations with a ray that
      goes from the bug to the light and collides with objects and cubes
      of impedance representing environment cells.  Then we just add up
      all the impedances from all of the collisions.

Phase 3 and Beyond

   1. Create a whole new concept of actuators.  How about giving the
      bugs actual arms, and letting the bugs control joint rotations. 
      This will give us a mechanism to allow bugs to grab on to each
      other.  We are only limited here by our own imagination. 


Okay here's some of the bad news about this change, and we can discuss 
how important or unimportant these issues are:

   1. The world won't wrap anymore. 
   2. Audio stimuli needs to be rethought, since it won't quite work as
      well anymore.  I'm thinking to just represent audio and a sphere
      which radius grows, and we can use the "Sensor Space" of phase 2
      to determine when a bug senses audio.  We can use the ray method
      to calculate audio impedances

Tell me what you guys think =)
Rob