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1 #+title: Movement!
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2 #+author: Robert McIntyre
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3 #+email: rlm@mit.edu
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4 #+description: muscles for a simulated creature
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5 #+keywords: simulation, jMonkeyEngine3, clojure
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6 #+SETUPFILE: ../../aurellem/org/setup.org
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7 #+INCLUDE: ../../aurellem/org/level-0.org
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8
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9
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10 Surprisingly enough, terristerial creatures only move by using torque
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11 applied about their joints. There's not a single straight line of
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12 force in the human body at all! (A straight line of force would
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13 correspond to some sort of jet or rocket propulseion.)
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14
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15
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16 Here's how motor-control/ proprioception will work: Each muscle is
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17 defined by a 1-D array of numbers (the "motor pool") each of which
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18 represent muscle fibers. A muscle also has a scalar :strength factor
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19 which determines how strong the muscle as a whole is. The effector
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20 function for a muscle takes a number < (count motor-pool) and that
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21 number is said to "activate" all the muscle fibers whose index is
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22 lower than the number. Each fiber will apply force in proportion to
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23 its value in the array. Lower values cause less force. The lower
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24 values can be put at the "beginning" of the 1-D array to simulate the
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25 layout of actual human muscles, which are capable of more percise
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26 movements when exerting less force.
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27
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28 #+name: movement
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29 #+begin_src clojure
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30 (ns cortex.movement
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31 "Give simulated creatures defined in special blender files the power
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32 to move around in a simulated environment."
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33 {:author "Robert McIntyre"}
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34 (:use (cortex world util sense body))
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35 (:use clojure.contrib.def)
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36 (:import java.awt.image.BufferedImage)
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37 (:import com.jme3.scene.Node)
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38 (:import com.jme3.math.Vector3f)
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39 (:import com.jme3.bullet.control.RigidBodyControl))
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40
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41 (defn muscle-profile
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42 "Return a vector where each entry is the strength of the \"motor
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43 pool\" at that part in the muscle."
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44 [#^BufferedImage profile]
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45 (vec
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46 (let [width (.getWidth profile)]
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47 (for [x (range width)]
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48 (- 255
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49 (bit-and
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50 0x0000FF
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51 (.getRGB profile x 0)))))))
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52
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53 (defvar
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54 ^{:arglists '([creature])}
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55 muscles
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56 (sense-nodes "muscles")
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57 "Return the children of the creature's \"muscles\" node.")
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58
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59 (defn movement-fn
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60 "Returns a function which when called with a integer value inside a
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61 running simulation, will cause movement in the creature according
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62 to the muscle's position and strength profile"
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63 [#^Node parts #^Node muscle]
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64 (let [target (closest-node parts muscle)
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65 axis
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66 (.mult (.getWorldRotation muscle) Vector3f/UNIT_Y)
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67 strength (meta-data muscle "strength")
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68 image-name (read-string (meta-data muscle "muscle"))
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69 image (load-image image-name)
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70 fibers (muscle-profile image)
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71 fiber-integral (reductions + fibers)
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72 force-index (vec
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73 (map
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74 #(float (* strength (/ % (last
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75 fiber-integral))))
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76 fiber-integral))
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77 control (.getControl target RigidBodyControl)]
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78 (fn [n]
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79 (let [pool-index (min n (count fibers))]
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80 (.applyTorque control (.mult axis (force-index n)))))))
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81
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82 (defn movement!
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83 "Endow the creature with the power of movement. Returns a sequence
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84 of functions, each of which accept an integer value and will
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85 activate their corresponding muscle."
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86 [#^Node creature]
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87 (for [muscle (muscles creature)]
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88 (movement-fn creature muscle)))
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89
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90
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91 #+end_src
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92
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93
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94
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95
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96
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97 * COMMENT code generation
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98 #+begin_src clojure :tangle ../src/cortex/movement.clj
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99 <<movement>>
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100 #+end_src
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