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1 #+title: The Sense of Proprioception
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2 #+author: Robert McIntyre
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3 #+email: rlm@mit.edu
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4 #+description: proprioception for simulated creatures
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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 * Proprioception
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10
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11 Close your eyes, and touch your nose with your right index finger. How
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12 did you do it? You could not see your hand, and neither your hand nor
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13 your nose could use the sense of touch to guide the path of your hand.
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14 There are no sound cues, and Taste and Smell certainly don't provide
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15 any help. You know where your hand is without your other senses
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16 because of Proprioception.
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17
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18 Humans can sometimes loose this sense through viral infections or
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19 damage to the spinal cord or brain, and when they do, they loose the
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20 ability to control their own bodies without looking directly at the
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21 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]],
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22 a woman named Christina looses this sense and has to learn how to move
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23 by carefully watching her arms and legs. She describes proprioception
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24 as the "eyes of the body, the way the body sees itself".
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25
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26 Proprioception in humans is mediated by [[http://en.wikipedia.org/wiki/Articular_capsule][joint capsules]], [[http://en.wikipedia.org/wiki/Muscle_spindle][muscle
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27 spindles]], and the [[http://en.wikipedia.org/wiki/Golgi_tendon_organ][Golgi tendon organs]]. These measure the relative
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28 positions of each pody part by monitoring muscle strain and length.
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29
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30 It's clear that this is a vital sense for fulid, graceful
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31 movement. It's also particurally easy to implement in jMonkeyEngine.
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32
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33 My simulated proprioception calculates the relative angles of each
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34 joint from the rest position defined in the blender file. This
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35 simulates the muscle-spindles and joint capsules. I will deal with
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36 Golgi tendon organs, which calculate muscle strain, in the [[./movement.org][next post]].
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37
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38 * Helper Functions
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39
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40 =(absolute-angle)= calculates the angle between two vectors, relative to a
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41 third axis vector. This angle is the number of radians you have to
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42 move counterclockwise around the axis vector to get from the first to
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43 the second vector. It is not commutative like a normal dot-product
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44 angle is.
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45
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46 #+name: helpers
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47 #+begin_src clojure
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48 (in-ns 'cortex.proprioception)
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49
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50 (defn right-handed?
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51 "true iff the three vectors form a right handed coordinate
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52 system. The three vectors do not have to be normalized or
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53 orthogonal."
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54 [vec1 vec2 vec3]
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55 (< 0 (.dot (.cross vec1 vec2) vec3)))
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56
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57 (defn absolute-angle
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58 "The angle between 'vec1 and 'vec2 around 'axis. In the range
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59 [0 (* 2 Math/PI)]."
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60 [vec1 vec2 axis]
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61 (let [angle (.angleBetween vec1 vec2)]
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62 (if (right-handed? vec1 vec2 axis)
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63 angle (- (* 2 Math/PI) angle))))
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64 #+end_src
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65
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66 #+begin_src clojure :exports both
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67 (in-ns 'cortex.proprioception)
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68 (absolute-angle Vector3f/UNIT_X Vector3f/UNIT_Y Vector3f/UNIT_Z)
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69 #+end_src
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70
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71 #+results:
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72 : 1.5707964
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73
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74 #+begin_src clojure :exports both
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75 (in-ns 'cortex.proprioception)
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76 (absolute-angle
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77 Vector3f/UNIT_X (.mult Vector3f/UNIT_Y (float -1)) Vector3f/UNIT_Z)
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78 #+end_src
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79
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80 #+results:
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81 : 4.7123889366733
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82
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83 * Proprioception Kernel
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84
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85 Given a joint, =(proprioception-kernel)= produces a function that
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86 calculates the euler angles between the the objects the joint
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87 connects.
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88
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89 #+name: proprioception
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90 #+begin_src clojure
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91 (defn proprioception-kernel
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92 "Returns a function which returns proprioceptive sensory data when
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93 called inside a running simulation."
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94 [#^Node parts #^Node joint]
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95 (let [[obj-a obj-b] (joint-targets parts joint)
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96 joint-rot (.getWorldRotation joint)
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97 x0 (.mult joint-rot Vector3f/UNIT_X)
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98 y0 (.mult joint-rot Vector3f/UNIT_Y)
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99 z0 (.mult joint-rot Vector3f/UNIT_Z)]
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100 (fn []
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101 (let [rot-a (.clone (.getWorldRotation obj-a))
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102 rot-b (.clone (.getWorldRotation obj-b))
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103 x (.mult rot-a x0)
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104 y (.mult rot-a y0)
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105 z (.mult rot-a z0)
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106
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107 X (.mult rot-b x0)
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108 Y (.mult rot-b y0)
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109 Z (.mult rot-b z0)
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110 heading (Math/atan2 (.dot X z) (.dot X x))
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111 pitch (Math/atan2 (.dot X y) (.dot X x))
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112
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113 ;; rotate x-vector back to origin
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114 reverse
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115 (doto (Quaternion.)
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116 (.fromAngleAxis
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117 (.angleBetween X x)
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118 (let [cross (.normalize (.cross X x))]
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119 (if (= 0 (.length cross)) y cross))))
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120 roll (absolute-angle (.mult reverse Y) y x)]
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121 [heading pitch roll]))))
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122
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123 (defn proprioception!
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124 "Endow the creature with the sense of proprioception. Returns a
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125 sequence of functions, one for each child of the \"joints\" node in
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126 the creature, which each report proprioceptive information about
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127 that joint."
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128 [#^Node creature]
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129 ;; extract the body's joints
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130 (let [senses (map (partial proprioception-kernel creature)
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131 (joints creature))]
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132 (fn []
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133 (map #(%) senses))))
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134 #+end_src
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135
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136
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137 =(proprioception!)= maps =(proprioception-kernel)= across all the
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138 joints of the creature. It uses the same list of joints that
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139 =(cortex.body/joints)= uses.
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140
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141 * Visualizing Proprioception
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142
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143 Proprioception has the lowest bandwidth of all the senses so far, and
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144 it doesn't lend itself as readily to visual representation like
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145 vision, hearing, or touch. This visualization code creates a "guage"
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146 to view each of the three relative angles along a circle.
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147
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148 #+name: visualize
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149 #+begin_src clojure
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150 (in-ns 'cortex.proprioception)
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151
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152 (defn draw-sprite [image sprite x y color ]
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153 (dorun
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154 (for [[u v] sprite]
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155 (.setRGB image (+ u x) (+ v y) color))))
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156
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157 (defn view-angle
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158 "create a debug view of an angle"
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159 [color]
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160 (let [image (BufferedImage. 50 50 BufferedImage/TYPE_INT_RGB)
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161 previous (atom [25 25])
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162 sprite [[0 0] [0 1]
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163 [0 -1] [-1 0] [1 0]]]
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164 (fn [angle]
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165 (let [angle (float angle)]
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166 (let [position
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167 [(+ 25 (int (* 20 (Math/cos angle))))
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168 (+ 25 (int (* -20 (Math/sin angle))))]]
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169 (draw-sprite image sprite (@previous 0) (@previous 1) 0x000000)
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170 (draw-sprite image sprite (position 0) (position 1) color)
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171 (reset! previous position))
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172 image))))
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173
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174 (defn proprioception-display-kernel
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175 "Display proprioception angles in a BufferedImage"
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176 [[h p r]]
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177 (let [image (BufferedImage. 50 50 BufferedImage/TYPE_INT_RGB)
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178 previous-heading (atom [25 25])
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179 previous-pitch (atom [25 25])
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180 previous-roll (atom [25 25])
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181
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182 heading-sprite [[0 0] [0 1] [0 -1] [-1 0] [1 0]]
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183 pitch-sprite [[0 0] [0 1] [0 -1] [-1 0] [1 0]]
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184 roll-sprite [[0 0] [0 1] [0 -1] [-1 0] [1 0]]
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185 draw-angle
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186 (fn [angle sprite previous color]
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187 (let [angle (float angle)]
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188 (let [position
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189 [(+ 25 (int (* 20 (Math/cos angle))))
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190 (+ 25 (int (* -20 (Math/sin angle))))]]
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191 (draw-sprite image sprite (@previous 0) (@previous 1) 0x000000)
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192 (draw-sprite image sprite (position 0) (position 1) color)
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193 (reset! previous position))
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194 image))]
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195 (dorun (map draw-angle
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196 [h p r]
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197 [heading-sprite pitch-sprite roll-sprite]
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198 [previous-heading previous-pitch previous-roll]
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199 [0xFF0000 0x00FF00 0xFFFFFF]))
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200 image))
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201
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202 (defn view-proprioception
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203 "Creates a function which accepts a list of proprioceptive data and
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204 display each element of the list to the screen as an image."
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205 []
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206 (view-sense proprioception-display-kernel))
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207 #+end_src
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208
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209 * Proprioception Test
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210 This test does not use the worm, but instead uses two bars, bound
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211 together by a point2point joint. One bar is fixed, and I control the
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212 other bar from the keyboard.
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213
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214 #+name: test-proprioception
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215 #+begin_src clojure
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216 (in-ns 'cortex.test.proprioception)
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217
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218 (defn test-proprioception
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219 "Testing proprioception:
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220 You should see two foating bars, and a printout of pitch, yaw, and
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221 roll. Pressing key-r/key-t should move the blue bar up and down and
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222 change only the value of pitch. key-f/key-g moves it side to side
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223 and changes yaw. key-v/key-b will spin the blue segment clockwise
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224 and counterclockwise, and only affect roll."
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225 ([] (test-proprioception false))
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226 ([record?]
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227 (let [hand (box 0.2 1 0.2 :position (Vector3f. 0 0 0)
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228 :mass 0 :color ColorRGBA/Gray :name "hand")
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229 finger (box 0.2 1 0.2 :position (Vector3f. 0 2.4 0)
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230 :mass 1
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231 :color
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232 (ColorRGBA. (/ 184 255) (/ 127 255) (/ 201 255) 1)
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233 :name "finger")
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234 joint-node (box 0.1 0.05 0.05 :color ColorRGBA/Yellow
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235 :position (Vector3f. 0 1.2 0)
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236 :rotation (doto (Quaternion.)
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237 (.fromAngleAxis
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238 (/ Math/PI 2)
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239 (Vector3f. 0 0 1)))
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240 :physical? false)
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241 creature (nodify [hand finger joint-node])
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242 finger-control (.getControl finger RigidBodyControl)
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243 hand-control (.getControl hand RigidBodyControl)
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244 joint (joint-dispatch {:type :point} hand-control finger-control
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245 (Vector3f. 0 1.2 0)
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246 (Vector3f. 0 -1.2 0) nil)
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247
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248 root (nodify [creature])
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249 prop (proprioception-kernel creature joint-node)
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250 prop-view (view-proprioception)]
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251 (.setCollisionGroup
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252 (.getControl hand RigidBodyControl)
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253 PhysicsCollisionObject/COLLISION_GROUP_NONE)
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254 (apply
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255 world
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256 (with-movement
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257 finger
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258 ["key-r" "key-t" "key-f" "key-g" "key-v" "key-b"]
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259 [1 1 10 10 10 10]
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260 [root
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261 standard-debug-controls
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262 (fn [world]
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263 (if record?
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264 (Capture/captureVideo
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265 world
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266 (File. "/home/r/proj/cortex/render/proprio/main-view")))
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267 (.setTimer world (com.aurellem.capture.RatchetTimer. 60))
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268 (set-gravity world (Vector3f. 0 0 0))
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269 (enable-debug world)
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270 (light-up-everything world))
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271 (fn [_ _]
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272 (prop-view
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273 (list (prop))
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274 (if record?
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275 (File. "/home/r/proj/cortex/render/proprio/proprio"))))])))))
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276 #+end_src
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277
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278 #+results: test-proprioception
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279 : #'cortex.test.proprioception/test-proprioception
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280
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281 * Video of Proprioception
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282
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283 #+begin_html
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284 <div class="figure">
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285 <center>
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286 <video controls="controls" width="550">
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287 <source src="../video/test-proprioception.ogg" type="video/ogg"
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288 preload="none" poster="../images/aurellem-1280x480.png" />
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289 </video>
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290 </center>
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291 <p>Proprioception in a simple creature. The proprioceptive readout is
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292 in the upper left corner of the screen.</p>
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293 </div>
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294 #+end_html
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295
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296 ** Generating the Proprioception Video
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297 #+name: magick6
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298 #+begin_src clojure
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299 (ns cortex.video.magick6
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300 (:import java.io.File)
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301 (:use clojure.contrib.shell-out))
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302
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303 (defn images [path]
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304 (sort (rest (file-seq (File. path)))))
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305
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306 (def base "/home/r/proj/cortex/render/proprio/")
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307
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308 (defn pics [file]
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309 (images (str base file)))
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310
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311 (defn combine-images []
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312 (let [main-view (pics "main-view")
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313 proprioception (pics "proprio/0")
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314 targets (map
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315 #(File. (str base "out/" (format "%07d.png" %)))
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316 (range 0 (count main-view)))]
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317 (dorun
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318 (pmap
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319 (comp
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320 (fn [[ main-view proprioception target]]
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321 (println target)
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322 (sh "convert"
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323 main-view
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324 proprioception "-geometry" "+20+20" "-composite"
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325 target))
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326 (fn [& args] (map #(.getCanonicalPath %) args)))
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327 main-view proprioception targets))))
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328 #+end_src
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329
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330 #+begin_src sh :results silent
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331 cd ~/proj/cortex/render/proprio
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332 ffmpeg -r 60 -i out/%07d.png -b:v 9000k -c:v libtheora \
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333 test-proprioception.ogg
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334 #+end_src
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335
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336 * Headers
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337 #+name: proprioception-header
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338 #+begin_src clojure
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339 (ns cortex.proprioception
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340 "Simulate the sense of proprioception (ability to detect the
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341 relative positions of body parts with repsect to other body parts)
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342 in jMonkeyEngine3. Reads specially prepared blender files to
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343 automatically generate proprioceptive senses."
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344 (:use (cortex world util sense body))
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345 (:use clojure.contrib.def)
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346 (:import com.jme3.scene.Node)
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347 (:import java.awt.image.BufferedImage)
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348 (:import (com.jme3.math Vector3f Quaternion)))
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349 #+end_src
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350
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351 #+name: test-proprioception-header
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352 #+begin_src clojure
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353 (ns cortex.test.proprioception
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354 (:import (com.aurellem.capture Capture RatchetTimer))
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355 (:use (cortex util world proprioception body))
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356 (:import java.io.File))
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357 (cortex.import/mega-import-jme3)
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358 #+end_src
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359
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360 * Source Listing
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361 - [[../src/cortex/proprioception.clj][cortex.proprioception]]
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362 - [[../src/cortex/test/touch.clj][cortex.test.proprioception]]
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363 - [[../src/cortex/video/magick6.clj][cortex.video.magick6]]
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364 #+html: <ul> <li> <a href="../org/proprioception.org">This org file</a> </li> </ul>
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365 - [[http://hg.bortreb.com ][source-repository]]
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366
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367 * Next
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368
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369 Next time, I'll give the Worm the power to [[./movement.org][move on it's own]].
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370
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371
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372 * COMMENT generate source
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373 #+begin_src clojure :tangle ../src/cortex/proprioception.clj
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374 <<proprioception-header>>
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375 <<helpers>>
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376 <<proprioception>>
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377 <<visualize>>
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378 #+end_src
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379
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380 #+begin_src clojure :tangle ../src/cortex/test/proprioception.clj
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381 <<test-proprioception-header>>
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382 <<test-proprioception>>
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383 #+end_src
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384
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385 #+begin_src clojure :tangle ../src/cortex/video/magick6.clj
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386 <<magick6>>
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387 #+end_src
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