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fixed termonology in movement.org
author Robert McIntyre <rlm@mit.edu>
date Thu, 16 Feb 2012 07:25:03 -0700
parents 23aadf376e9d
children 67a4e92d4628
rev   line source
rlm@260 1 #+title: Simulated Muscles
rlm@158 2 #+author: Robert McIntyre
rlm@158 3 #+email: rlm@mit.edu
rlm@158 4 #+description: muscles for a simulated creature
rlm@158 5 #+keywords: simulation, jMonkeyEngine3, clojure
rlm@158 6 #+SETUPFILE: ../../aurellem/org/setup.org
rlm@158 7 #+INCLUDE: ../../aurellem/org/level-0.org
rlm@158 8
rlm@180 9
rlm@260 10 * Muscles
rlm@260 11
rlm@180 12 Surprisingly enough, terristerial creatures only move by using torque
rlm@180 13 applied about their joints. There's not a single straight line of
rlm@180 14 force in the human body at all! (A straight line of force would
rlm@260 15 correspond to some sort of jet or rocket propulsion.)
rlm@180 16
rlm@278 17 In humans, muscles are composed of muscle fibers which can contract to
rlm@278 18 exert force. The muscle fibers which compose a muscle are partitioned
rlm@278 19 into discrete groups which are each controlled by a single alpha motor
rlm@278 20 neuton. A single alpha motor neuron might control as little as three
rlm@278 21 or as many as one thousand muscle fibers. When the alpha motor neuron
rlm@278 22 is engaged by the spinal cord, it activates all of the muscle fibers
rlm@278 23 to which it is attached. The spinal cord generally engages the alpha
rlm@278 24 motor neurons which control few muscle fibers before the motor neurons
rlm@278 25 which control many muscle fibers. This recruitment stragety allows
rlm@278 26 for percise movements at low strength. The collection of all motor
rlm@278 27 neurons that control a muscle is called the motor pool. The brain
rlm@278 28 essentially says "activate 30% of the motor pool" and the spinal cord
rlm@278 29 recruits motor neurons untill 30% are activated. Since the
rlm@278 30 distribution of power among motor neurons is unequal and recruitment
rlm@278 31 goes from weakest to strongest, the first 30% of the motor pool might
rlm@278 32 be 5% of the strength of the muscle.
rlm@260 33
rlm@260 34 My simulated muscles follow a similiar design: Each muscle is defined
rlm@267 35 by a 1-D array of numbers (the "motor pool"). Each entry in the array
rlm@278 36 represents a motor neuron which controlls a number of muscle fibers
rlm@278 37 equal to the value of the entry. Each muscle has a scalar strength
rlm@278 38 factor which determines the total force the muscle can exert when all
rlm@278 39 motor neurons are activated. The effector function for a muscle takes
rlm@278 40 a number to index into the motor pool, and then "activates" all the
rlm@278 41 motor neurons whose index is lower or equal to the number. Each
rlm@267 42 motor-neuron will apply force in proportion to its value in the array.
rlm@267 43 Lower values cause less force. The lower values can be put at the
rlm@267 44 "beginning" of the 1-D array to simulate the layout of actual human
rlm@267 45 muscles, which are capable of more percise movements when exerting
rlm@267 46 less force. Or, the motor pool can simulate more exoitic recruitment
rlm@267 47 strageties which do not correspond to human muscles.
rlm@260 48
rlm@260 49 This 1D array is defined in an image file for ease of
rlm@260 50 creation/visualization. Here is an example muscle profile image.
rlm@260 51
rlm@260 52 #+caption: A muscle profile image that describes the strengths of each motor neuron in a muscle. White is weakest and dark red is strongest. This particular pattern has weaker motor neurons at the beginning, just like human muscle.
rlm@260 53 [[../images/basic-muscle.png]]
rlm@260 54
rlm@260 55 * Blender Meta-data
rlm@260 56
rlm@260 57 In blender, each muscle is an empty node whose top level parent is
rlm@260 58 named "muscles", just like eyes, ears, and joints.
rlm@260 59
rlm@260 60 These functions define the expected meta-data for a muscle node.
rlm@180 61
rlm@261 62 #+name: muscle-meta-data
rlm@158 63 #+begin_src clojure
rlm@260 64 (in-ns 'cortex.movement)
rlm@158 65
rlm@180 66 (defvar
rlm@180 67 ^{:arglists '([creature])}
rlm@180 68 muscles
rlm@180 69 (sense-nodes "muscles")
rlm@180 70 "Return the children of the creature's \"muscles\" node.")
rlm@158 71
rlm@260 72 (defn muscle-profile-image
rlm@260 73 "Get the muscle-profile image from the node's blender meta-data."
rlm@260 74 [#^Node muscle]
rlm@260 75 (if-let [image (meta-data muscle "muscle")]
rlm@260 76 (load-image image)))
rlm@260 77
rlm@260 78 (defn muscle-strength
rlm@260 79 "Return the strength of this muscle, or 1 if it is not defined."
rlm@260 80 [#^Node muscle]
rlm@260 81 (if-let [strength (meta-data muscle "strength")]
rlm@260 82 strength 1))
rlm@260 83
rlm@260 84 (defn motor-pool
rlm@260 85 "Return a vector where each entry is the strength of the \"motor
rlm@260 86 neuron\" at that part in the muscle."
rlm@260 87 [#^Node muscle]
rlm@260 88 (let [profile (muscle-profile-image muscle)]
rlm@260 89 (vec
rlm@260 90 (let [width (.getWidth profile)]
rlm@260 91 (for [x (range width)]
rlm@260 92 (- 255
rlm@260 93 (bit-and
rlm@260 94 0x0000FF
rlm@260 95 (.getRGB profile x 0))))))))
rlm@260 96 #+end_src
rlm@260 97
rlm@273 98 Of note here is =motor-pool= which interprets the muscle-profile
rlm@260 99 image in a way that allows me to use gradients between white and red,
rlm@260 100 instead of shades of gray as I've been using for all the other
rlm@260 101 senses. This is purely an aesthetic touch.
rlm@260 102
rlm@260 103 * Creating Muscles
rlm@261 104 #+name: muscle-kernel
rlm@260 105 #+begin_src clojure
rlm@261 106 (in-ns 'cortex.movement)
rlm@261 107
rlm@260 108 (defn movement-kernel
rlm@180 109 "Returns a function which when called with a integer value inside a
rlm@191 110 running simulation will cause movement in the creature according
rlm@191 111 to the muscle's position and strength profile. Each function
rlm@191 112 returns the amount of force applied / max force."
rlm@260 113 [#^Node creature #^Node muscle]
rlm@260 114 (let [target (closest-node creature muscle)
rlm@158 115 axis
rlm@158 116 (.mult (.getWorldRotation muscle) Vector3f/UNIT_Y)
rlm@260 117 strength (muscle-strength muscle)
rlm@260 118
rlm@260 119 pool (motor-pool muscle)
rlm@260 120 pool-integral (reductions + pool)
rlm@191 121 force-index
rlm@260 122 (vec (map #(float (* strength (/ % (last pool-integral))))
rlm@260 123 pool-integral))
rlm@158 124 control (.getControl target RigidBodyControl)]
rlm@158 125 (fn [n]
rlm@260 126 (let [pool-index (max 0 (min n (dec (count pool))))
rlm@191 127 force (force-index pool-index)]
rlm@191 128 (.applyTorque control (.mult axis force))
rlm@191 129 (float (/ force strength))))))
rlm@158 130
rlm@180 131 (defn movement!
rlm@180 132 "Endow the creature with the power of movement. Returns a sequence
rlm@180 133 of functions, each of which accept an integer value and will
rlm@180 134 activate their corresponding muscle."
rlm@158 135 [#^Node creature]
rlm@180 136 (for [muscle (muscles creature)]
rlm@260 137 (movement-kernel creature muscle)))
rlm@260 138 #+end_src
rlm@158 139
rlm@273 140 =movement-kernel= creates a function that will move the nearest
rlm@260 141 physical object to the muscle node. The muscle exerts a rotational
rlm@260 142 force dependant on it's orientation to the object in the blender
rlm@273 143 file. The function returned by =movement-kernel= is also a sense
rlm@260 144 function: it returns the percent of the total muscle strength that is
rlm@260 145 currently being employed. This is analogous to muscle tension in
rlm@260 146 humans and completes the sense of proprioception begun in the last
rlm@260 147 post.
rlm@260 148
rlm@260 149 * Visualizing Muscle Tension
rlm@260 150 Muscle exertion is a percent of a total, so the visulazation is just a
rlm@260 151 simple percent bar.
rlm@260 152
rlm@261 153 #+name: visualization
rlm@260 154 #+begin_src clojure
rlm@191 155 (defn movement-display-kernel
rlm@191 156 "Display muscle exertion data as a bar filling up with red."
rlm@191 157 [exertion]
rlm@191 158 (let [height 20
rlm@191 159 width 300
rlm@191 160 image (BufferedImage. width height
rlm@191 161 BufferedImage/TYPE_INT_RGB)
rlm@191 162 fill (min (int (* width exertion)) width)]
rlm@191 163 (dorun
rlm@191 164 (for [x (range fill)
rlm@191 165 y (range height)]
rlm@191 166 (.setRGB image x y 0xFF0000)))
rlm@191 167 image))
rlm@191 168
rlm@191 169 (defn view-movement
rlm@191 170 "Creates a function which accepts a list of muscle-exertion data and
rlm@191 171 displays each element of the list to the screen."
rlm@191 172 []
rlm@191 173 (view-sense movement-display-kernel))
rlm@158 174 #+end_src
rlm@158 175
rlm@260 176 * Adding Touch to the Worm
rlm@158 177
rlm@278 178 To the worm, I add two new nodes which describe a single muscle.
rlm@277 179
rlm@277 180 #+attr_html: width=755
rlm@277 181 #+caption: The node highlighted in orange is the parent node of all muscles in the worm. The arrow highlighted in yellow represents the creature's single muscle, which moves the top segment. The other nodes which are not highlighted are joints, eyes, and ears.
rlm@277 182 [[../images/worm-with-muscle.png]]
rlm@277 183
rlm@283 184 #+name: test-movement
rlm@261 185 #+begin_src clojure
rlm@283 186 (defn test-worm-movement
rlm@283 187 ([] (test-worm-movement false))
rlm@261 188 ([record?]
rlm@261 189 (let [creature (doto (worm) (body!))
rlm@261 190
rlm@261 191 muscle-exertion (atom 0)
rlm@261 192 muscles (movement! creature)
rlm@261 193 muscle-display (view-movement)]
rlm@261 194 (.setMass
rlm@261 195 (.getControl (.getChild creature "worm-11") RigidBodyControl)
rlm@261 196 (float 0))
rlm@261 197 (world
rlm@261 198 (nodify [creature (floor)])
rlm@261 199 (merge standard-debug-controls
rlm@261 200 {"key-h"
rlm@261 201 (fn [_ value]
rlm@261 202 (if value
rlm@261 203 (swap! muscle-exertion (partial + 20))))
rlm@261 204 "key-n"
rlm@261 205 (fn [_ value]
rlm@261 206 (if value
rlm@261 207 (swap! muscle-exertion (fn [v] (- v 20)))))})
rlm@261 208 (fn [world]
rlm@261 209 (if record?
rlm@261 210 (Capture/captureVideo
rlm@261 211 world
rlm@261 212 (File. "/home/r/proj/cortex/render/worm-muscles/main-view")))
rlm@261 213 (light-up-everything world)
rlm@261 214 (enable-debug world)
rlm@261 215 (.setTimer world (RatchetTimer. 60))
rlm@261 216 (set-gravity world (Vector3f. 0 0 0))
rlm@261 217 (.setLocation (.getCamera world)
rlm@261 218 (Vector3f. -4.912815, 2.004171, 0.15710819))
rlm@261 219 (.setRotation (.getCamera world)
rlm@261 220 (Quaternion. 0.13828252, 0.65516764,
rlm@278 221 -0.12370994, 0.7323449)))
rlm@261 222 (fn [world tpf]
rlm@261 223 (muscle-display
rlm@261 224 (map #(% @muscle-exertion) muscles)
rlm@261 225 (if record?
rlm@261 226 (File. "/home/r/proj/cortex/render/worm-muscles/muscles"))))))))
rlm@261 227 #+end_src
rlm@261 228
rlm@261 229 * Video Demonstration
rlm@261 230
rlm@261 231 #+begin_html
rlm@261 232 <div class="figure">
rlm@261 233 <center>
rlm@261 234 <video controls="controls" width="550">
rlm@261 235 <source src="../video/worm-muscles.ogg" type="video/ogg"
rlm@261 236 preload="none" poster="../images/aurellem-1280x480.png" />
rlm@261 237 </video>
rlm@261 238 </center>
rlm@261 239 <p>The worm is now able to move. The bar in the lower right displays
rlm@261 240 the power output of the muscle . Each jump causes 20 more motor neurons to
rlm@261 241 be recruited. Notice that the power output increases non-linearly
rlm@261 242 with motror neuron recruitement, similiar to a human muscle.</p>
rlm@261 243 </div>
rlm@261 244 #+end_html
rlm@261 245
rlm@261 246 ** Making the Worm Muscles Video
rlm@261 247 #+name: magick7
rlm@261 248 #+begin_src clojure
rlm@261 249 (ns cortex.video.magick7
rlm@261 250 (:import java.io.File)
rlm@261 251 (:use clojure.contrib.shell-out))
rlm@261 252
rlm@261 253 (defn images [path]
rlm@261 254 (sort (rest (file-seq (File. path)))))
rlm@261 255
rlm@261 256 (def base "/home/r/proj/cortex/render/worm-muscles/")
rlm@261 257
rlm@261 258 (defn pics [file]
rlm@261 259 (images (str base file)))
rlm@261 260
rlm@261 261 (defn combine-images []
rlm@261 262 (let [main-view (pics "main-view")
rlm@261 263 muscles (pics "muscles/0")
rlm@261 264 targets (map
rlm@261 265 #(File. (str base "out/" (format "%07d.png" %)))
rlm@261 266 (range 0 (count main-view)))]
rlm@261 267 (dorun
rlm@261 268 (pmap
rlm@261 269 (comp
rlm@261 270 (fn [[ main-view muscles target]]
rlm@261 271 (println target)
rlm@261 272 (sh "convert"
rlm@261 273 main-view
rlm@261 274 muscles "-geometry" "+320+440" "-composite"
rlm@261 275 target))
rlm@261 276 (fn [& args] (map #(.getCanonicalPath %) args)))
rlm@261 277 main-view muscles targets))))
rlm@261 278 #+end_src
rlm@261 279
rlm@261 280 #+begin_src sh :results silent
rlm@261 281 cd ~/proj/cortex/render/worm-muscles
rlm@261 282 ffmpeg -r 60 -i out/%07d.png -b:v 9000k -c:v libtheora worm-muscles.ogg
rlm@261 283 #+end_src
rlm@158 284
rlm@260 285 * Headers
rlm@260 286 #+name: muscle-header
rlm@260 287 #+begin_src clojure
rlm@260 288 (ns cortex.movement
rlm@260 289 "Give simulated creatures defined in special blender files the power
rlm@260 290 to move around in a simulated environment."
rlm@260 291 {:author "Robert McIntyre"}
rlm@260 292 (:use (cortex world util sense body))
rlm@260 293 (:use clojure.contrib.def)
rlm@260 294 (:import java.awt.image.BufferedImage)
rlm@260 295 (:import com.jme3.scene.Node)
rlm@260 296 (:import com.jme3.math.Vector3f)
rlm@260 297 (:import com.jme3.bullet.control.RigidBodyControl))
rlm@260 298 #+end_src
rlm@260 299
rlm@261 300 #+name: test-header
rlm@261 301 #+begin_src clojure
rlm@261 302 (ns cortex.test.movement
rlm@261 303 (:use (cortex world util sense body movement))
rlm@261 304 (:use cortex.test.body)
rlm@261 305 (:use clojure.contrib.def)
rlm@261 306 (:import java.io.File)
rlm@261 307 (:import java.awt.image.BufferedImage)
rlm@261 308 (:import com.jme3.scene.Node)
rlm@283 309 (:import (com.jme3.math Quaternion Vector3f))
rlm@261 310 (:import (com.aurellem.capture Capture RatchetTimer))
rlm@261 311 (:import com.jme3.bullet.control.RigidBodyControl))
rlm@261 312 #+end_src
rlm@261 313
rlm@261 314 * Source Listing
rlm@261 315 - [[../src/cortex/movement.clj][cortex.movement]]
rlm@261 316 - [[../src/cortex/test/movement.clj][cortex.test.movement]]
rlm@261 317 - [[../src/cortex/video/magick7.clj][cortex.video.magick7]]
rlm@261 318 #+html: <ul> <li> <a href="../org/movement.org">This org file</a> </li> </ul>
rlm@261 319 - [[http://hg.bortreb.com ][source-repository]]
rlm@158 320
rlm@158 321 * COMMENT code generation
rlm@158 322 #+begin_src clojure :tangle ../src/cortex/movement.clj
rlm@261 323 <<muscle-header>>
rlm@261 324 <<muscle-meta-data>>
rlm@261 325 <<muscle-kernel>>
rlm@261 326 <<visualization>>
rlm@158 327 #+end_src
rlm@261 328
rlm@261 329 #+begin_src clojure :tangle ../src/cortex/test/movement.clj
rlm@261 330 <<test-header>>
rlm@261 331 <<test-movement>>
rlm@261 332 #+end_src
rlm@261 333
rlm@261 334 #+begin_src clojure :tangle ../src/cortex/video/magick7.clj
rlm@261 335 <<magick7>>
rlm@261 336 #+end_src