cortex: thesis/cortex.org comparison

comparison thesis/cortex.org @ 479:a5480a06d5fe

first draft of proprioception complete.

author	Robert McIntyre <rlm@mit.edu>
date	Fri, 28 Mar 2014 23:16:32 -0400
parents	ba54df21fc7c
children	ad76b8b05517

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 #+caption:
 #+caption:
 #+caption:
 #+name: name
 #+begin_listing clojure
+#+BEGIN_SRC clojure
+#+END_SRC
 #+end_listing
 #+caption:
 #+caption:
 #+caption:
 #+ATTR_LaTeX: :width 15cm
 [[./images/touch-cube.png]]
 ** Proprioception is the sense that makes everything ``real''
+Close your eyes, and touch your nose with your right index finger.
+How did you do it? You could not see your hand, and neither your
+hand nor your nose could use the sense of touch to guide the path
+of your hand. There are no sound cues, and Taste and Smell
+certainly don't provide any help. You know where your hand is
+without your other senses because of Proprioception.
+Humans can sometimes loose this sense through viral infections or
+damage to the spinal cord or brain, and when they do, they loose
+the ability to control their own bodies without looking directly at
+the parts they want to move. In [[http://en.wikipedia.org/wiki/The_Man_Who_Mistook_His_Wife_for_a_Hat][The Man Who Mistook His Wife for a
+Hat]], a woman named Christina looses this sense and has to learn how
+to move by carefully watching her arms and legs. She describes
+proprioception as the "eyes of the body, the way the body sees
+itself".
+Proprioception in humans is mediated by [[http://en.wikipedia.org/wiki/Articular_capsule][joint capsules]], [[http://en.wikipedia.org/wiki/Muscle_spindle][muscle
+spindles]], and the [[http://en.wikipedia.org/wiki/Golgi_tendon_organ][Golgi tendon organs]]. These measure the relative
+positions of each body part by monitoring muscle strain and length.
+It's clear that this is a vital sense for fluid, graceful movement.
+It's also particularly easy to implement in jMonkeyEngine.
+My simulated proprioception calculates the relative angles of each
+joint from the rest position defined in the blender file. This
+simulates the muscle-spindles and joint capsules. I will deal with
+Golgi tendon organs, which calculate muscle strain, in the next
+section.
+*** Helper functions
+=absolute-angle= calculates the angle between two vectors,
+relative to a third axis vector. This angle is the number of
+radians you have to move counterclockwise around the axis vector
+to get from the first to the second vector. It is not commutative
+like a normal dot-product angle is.
+The purpose of these functions is to build a system of angle
+measurement that is biologically plausable.
+#+caption: Program to measure angles along a vector
+#+name: helpers
+#+begin_listing clojure
+#+BEGIN_SRC clojure
+(defn right-handed?
+"true iff the three vectors form a right handed coordinate
+system. The three vectors do not have to be normalized or
+orthogonal."
+[vec1 vec2 vec3]
+(pos? (.dot (.cross vec1 vec2) vec3)))
+(defn absolute-angle
+"The angle between 'vec1 and 'vec2 around 'axis. In the range
+[0 (* 2 Math/PI)]."
+[vec1 vec2 axis]
+(let [angle (.angleBetween vec1 vec2)]
+(if (right-handed? vec1 vec2 axis)
+angle (- (* 2 Math/PI) angle))))
+#+END_SRC
+#+end_listing
+#+caption:
+#+caption:
+#+caption:
+#+caption:
+#+name: name
+#+begin_listing clojure
+#+BEGIN_SRC clojure
+#+END_SRC
+#+end_listing
+*** Proprioception Kernel
+Given a joint, =proprioception-kernel= produces a function that
+calculates the Euler angles between the the objects the joint
+connects. The only tricky part here is making the angles relative
+to the joint's initial ``straightness''.
+#+caption: Program to return biologially reasonable proprioceptive
+#+caption: data for each joint.
+#+name: proprioception
+#+begin_listing clojure
+#+BEGIN_SRC clojure
+(defn proprioception-kernel
+"Returns a function which returns proprioceptive sensory data when
+called inside a running simulation."
+[#^Node parts #^Node joint]
+(let [[obj-a obj-b] (joint-targets parts joint)
+joint-rot (.getWorldRotation joint)
+x0 (.mult joint-rot Vector3f/UNIT_X)
+y0 (.mult joint-rot Vector3f/UNIT_Y)
+z0 (.mult joint-rot Vector3f/UNIT_Z)]
+(fn []
+(let [rot-a (.clone (.getWorldRotation obj-a))
+rot-b (.clone (.getWorldRotation obj-b))
+x (.mult rot-a x0)
+y (.mult rot-a y0)
+z (.mult rot-a z0)
+X (.mult rot-b x0)
+Y (.mult rot-b y0)
+Z (.mult rot-b z0)
+heading  (Math/atan2 (.dot X z) (.dot X x))
+pitch  (Math/atan2 (.dot X y) (.dot X x))
+;; rotate x-vector back to origin
+reverse
+(doto (Quaternion.)
+(.fromAngleAxis
+(.angleBetween X x)
+(let [cross (.normalize (.cross X x))]
+(if (= 0 (.length cross)) y cross))))
+roll (absolute-angle (.mult reverse Y) y x)]
+[heading pitch roll]))))
+(defn proprioception!
+"Endow the creature with the sense of proprioception. Returns a
+sequence of functions, one for each child of the \"joints\" node in
+the creature, which each report proprioceptive information about
+that joint."
+[#^Node creature]
+;; extract the body's joints
+(let [senses (map (partial proprioception-kernel creature)
+(joints creature))]
+(fn []
+(map #(%) senses))))
+#+END_SRC
+#+end_listing
+=proprioception!= maps =proprioception-kernel= across all the
+joints of the creature. It uses the same list of joints that
+=joints= uses. Proprioception is the easiest sense to implement in
+=CORTEX=, and it will play a crucial role when efficiently
+implementing empathy.
+#+caption: In the upper right corner, the three proprioceptive
+#+caption: angle measurements are displayed. Red is yaw, Green is
+#+caption: pitch, and White is roll.
+#+name: proprio
+#+ATTR_LaTeX: :width 11cm
+[[./images/proprio.png]]
 ** Muscles are both effectors and sensors
 ** =CORTEX= brings complex creatures to life!
 ** =CORTEX= enables many possiblities for further research

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comparison thesis/cortex.org @ 479:a5480a06d5fe