#+title: Simulated Senses

 #+author: Robert McIntyre

 #+email: rlm@mit.edu

 #+description: Simulating senses for AI research using JMonkeyEngine3

 #+SETUPFILE: ../../aurellem/org/setup.org

 #+INCLUDE: ../../aurellem/org/level-0.org

 #+babel: :mkdirp yes :noweb yes

 

 * Background

 Artificial Intelligence has tried and failed for more than half a

 century to produce programs as flexible, creative, and "intelligent"

 as the human mind itself. Clearly, we are still missing some important

 ideas concerning intelligent programs or we would have strong AI

 already. What idea could be missing?

 

 When Turing first proposed his famous "Turing Test" in the

 groundbreaking paper [[./sources/turing.pdf][/Computing Machines and Intelligence/]], he gave

 little importance to how a computer program might interact with the

 world:

 

 #+BEGIN_QUOTE

 \ldquo{}We need not be too concerned about the legs, eyes, etc. The example of

 Miss Helen Keller shows that education can take place provided that

 communication in both directions between teacher and pupil can take

 place by some means or other.\rdquo{}

 #+END_QUOTE

 

 And from the example of Hellen Keller he went on to assume that the

 only thing a fledgling AI program could need by way of communication

 is a teletypewriter. But Hellen Keller did possess vision and hearing

 for the first few months of her life, and her tactile sense was far

 more rich than any text-stream could hope to achieve. She possessed a

 body she could move freely, and had continual access to the real world

 to learn from her actions.

 

 I believe that our programs are suffering from too little sensory

 input to become really intelligent. Imagine for a moment that you

 lived in a world completely cut off form all sensory stimulation. You

 have no eyes to see, no ears to hear, no mouth to speak. No body, no

 taste, no feeling whatsoever. The only sense you get at all is a

 single point of light, flickering on and off in the void. If this was

 your life from birth, you would never learn anything, and could never

 become intelligent. Actual humans placed in sensory deprivation

 chambers experience hallucinations and can begin to loose their sense

 of reality in as little as 15 minutes[sensory-deprivation]. Most of

 the time, the programs we write are in exactly this situation. They do

 not interface with cameras and microphones, and they do not control a

 real or simulated body or interact with any sort of world.

 

 

 * Simulation vs. Reality

 I want demonstrate that multiple senses are what enable

 intelligence. There are two ways of playing around with senses and

 computer programs:

 

 The first is to go entirely with simulation: virtual world, virtual

 character, virtual senses. The advantages are that when everything is

 a simulation, experiments in that simulation are absolutely

 reproducible. It's also easier to change the character and world to

 explore new situations and different sensory combinations.

 

 

 ** Issues with Simulation

 

 If the world is to be simulated on a computer, then not only do you

 have to worry about whether the character's senses are rich enough to

 learn from the world, but whether the world itself is rendered with

 enough detail and realism to give enough working material to the

 character's senses. To name just a few difficulties facing modern

 physics simulators: destructibility of the environment, simulation of

 water/other fluids, large areas, nonrigid bodies, lots of objects,

 smoke. I don't know of any computer simulation that would allow a

 character to take a rock and grind it into fine dust, then use that

 dust to make a clay sculpture, at least not without spending years

 calculating the interactions of every single small grain of

 dust. Maybe a simulated world with today's limitations doesn't provide

 enough richness for real intelligence to evolve.

 

 ** Issues with Reality

 

 The other approach for playing with senses is to hook your software up

 to real cameras, microphones, robots, etc., and let it loose in the

 real world. This has the advantage of eliminating concerns about

 simulating the world at the expense of increasing the complexity of

 implementing the senses. Instead of just grabbing the current rendered

 frame for processing, you have to use an actual camera with real

 lenses and interact with photons to get an image. It is much harder to

 change the character, which is now partly a physical robot of some

 sort, since doing so involves changing things around in the real world

 instead of modifying lines of code. While the real world is very rich

 and definitely provides enough stimulation for intelligence to develop

 as evidenced by our own existence, it is also uncontrollable in the

 sense that a particular situation cannot be recreated perfectly or

 saved for later use. It is harder to conduct science because it is

 harder to repeat an experiment. The worst thing about using the real

 world instead of a simulation is the matter of time. Instead of

 simulated time you get the constant and unstoppable flow of real

 time. This severely limits the sorts of software you can use to

 program the AI because all sense inputs must be handled in real

 time. Complicated ideas may have to be implemented in hardware or may

 simply be impossible given the current speed of our

 processors. Contrast this with a simulation, in which the flow of time

 in the simulated world can be slowed down to accommodate the

 limitations of the character's programming. In terms of cost, doing

 everything in software is far cheaper than building custom real-time

 hardware. All you need is a laptop and some patience.

 

 * Choose a Simulation Engine

 

 Mainly because of issues with controlling the flow of time, I chose to

 simulate both the world and the character. I set out to make a minimal

 world in which I could embed a character with multiple senses. My main

 goal is to make an environment where I can perform further experiments

 in simulated senses.

 

 As Carl Sagan once said, "If you wish to make an apple pie from

 scratch, you must first invent the universe." I examined many

 different 3D environments to try and find something I would use as the

 base for my simulation; eventually the choice came down to three

 engines: the Quake II engine, the Source Engine, and jMonkeyEngine.

 

 ** Quake II/Jake2

 

 I spent a bit more than a month working with the Quake II Engine from

 ID software to see if I could use it for my purposes. All the source

 code was released by ID software into the Public Domain several years

 ago, and as a result it has been ported and modified for many

 different reasons. This engine was famous for its advanced use of

 realistic shading and had decent and fast physics

 simulation. Researchers at Princeton [[http://www.nature.com/nature/journal/v461/n7266/pdf/nature08499.pdf][used this code]] to study spatial

 information encoding in the hippocampal cells of rats. Those

 researchers created a special Quake II level that simulated a maze,

 and added an interface where a mouse could run around inside a ball in

 various directions to move the character in the simulated maze. They

 measured hippocampal activity during this exercise to try and tease

 out the method in which spatial data was stored in that area of the

 brain. I find this promising because if a real living rat can interact

 with a computer simulation of a maze in the same way as it interacts

 with a real-world maze, then maybe that simulation is close enough to

 reality that a simulated sense of vision and motor control interacting

 with that simulation could reveal useful information about the real

 thing. It happens that there is a Java port of the original C source

 code called Jake2. The port demonstrates Java's OpenGL bindings and

 runs anywhere from 90% to 105% as fast as the C version. After

 reviewing much of the source of Jake2, I eventually rejected it

 because the engine is too tied to the concept of a first-person

 shooter game. One of the problems I had was that there does not seem

 to be any easy way to attach multiple cameras to a single

 character. There are also several physics clipping issues that are

 corrected in a way that only applies to the main character and does

 not apply to arbitrary objects. While there is a large community of

 level modders, I couldn't find a community to support using the engine

 to make new things.

 

 ** Source Engine

 

 The Source Engine evolved from the Quake II and Quake I engines and is

 used by Valve in the Half-Life series of games. The physics simulation

 in the Source Engine is quite accurate and probably the best out of

 all the engines I investigated. There is also an extensive community

 actively working with the engine. However, applications that use the

 Source Engine must be written in C++, the code is not open, it only

 runs on Windows, and the tools that come with the SDK to handle models

 and textures are complicated and awkward to use.

 

 ** jMonkeyEngine

 

 jMonkeyEngine is a new library for creating games in Java. It uses

 OpenGL to render to the screen and uses screengraphs to avoid drawing

 things that do not appear on the screen. It has an active community

 and several games in the pipeline. The engine was not built to serve

 any particular game but is instead meant to be used for any 3D

 game. After experimenting with each of these three engines and a few

 others for about 2 months I settled on jMonkeyEngine. I chose it

 because it had the most features out of all the open projects I looked

 at, and because I could then write my code in Clojure, an

 implementation of LISP that runs on the JVM...