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1 // ----------------------------------------------------------------------------
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2 //
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3 //
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4 // OpenSteer -- Steering Behaviors for Autonomous Characters
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5 //
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6 // Copyright (c) 2002-2003, Sony Computer Entertainment America
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7 // Original author: Craig Reynolds <craig_reynolds@playstation.sony.com>
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8 //
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9 // Permission is hereby granted, free of charge, to any person obtaining a
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10 // copy of this software and associated documentation files (the "Software"),
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11 // to deal in the Software without restriction, including without limitation
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12 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
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13 // and/or sell copies of the Software, and to permit persons to whom the
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14 // Software is furnished to do so, subject to the following conditions:
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15 //
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16 // The above copyright notice and this permission notice shall be included in
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17 // all copies or substantial portions of the Software.
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18 //
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19 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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20 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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21 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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22 // THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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23 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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24 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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25 // DEALINGS IN THE SOFTWARE.
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26 //
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27 //
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28 // ----------------------------------------------------------------------------
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29 //
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30 //
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31 // SteerLibraryMixin
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32 //
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33 // This mixin (class with templated superclass) adds the "steering library"
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34 // functionality to a given base class. SteerLibraryMixin assumes its base
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35 // class supports the Ship interface.
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36 //
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37 // 10-04-04 bk: put everything into the OpenSteer namespace
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38 // 02-06-03 cwr: create mixin (from "SteerMass")
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39 // 06-03-02 cwr: removed TS dependencies
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40 // 11-21-01 cwr: created
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41 //
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42 //
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43 // ----------------------------------------------------------------------------
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44 module openmelee.steer;
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45
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46 class Steer
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47 {
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48 // Constructor: initializes state
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49 this ()
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50 {
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51 // set inital state
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52 reset ();
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53 }
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54
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55 // reset state
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56 void reset (void)
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57 {
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58 // initial state of wander behavior
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59 wanderSide = 0;
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60 wanderUp = 0;
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61
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62 // default to non-gaudyPursuitAnnotation
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63 gaudyPursuitAnnotation = false;
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64 }
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65
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66 // -------------------------------------------------- steering behaviors
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67
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68 // Wander behavior
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69 float wanderSide;
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70 float wanderUp;
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71
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72 bzVec2 steerForWander (float dt) {
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73 // random walk wanderSide and wanderUp between -1 and +1
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74 float speed = 12 * dt; // maybe this (12) should be an argument?
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75 wanderSide = scalarRandomWalk (wanderSide, speed, -1, +1);
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76 wanderUp = scalarRandomWalk (wanderUp, speed, -1, +1);
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77
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78 // return a pure lateral steering vector: (+/-Side) + (+/-Up)
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79 return (side() * wanderSide) + (up() * wanderUp);
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80 }
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81
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82 // Seek behavior
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83 bzVec2 steerForSeek (bzVec2 target) {
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84 bzVec2 desiredVelocity = target - position;
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85 return desiredVelocity - velocity;
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86 }
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87
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88 // Flee behavior
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89 bzVec2 steerForFlee (bzVec2 target) {
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90 bzVec2 desiredVelocity = position - target;
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91 return desiredVelocity - velocity();
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92 }
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93
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94 // xxx proposed, experimental new seek/flee [cwr 9-16-02]
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95 bzVec2 xxxsteerForFlee (bzVec2 target) {
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96 bzVec2 offset = position - target;
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97 bzVec2 desiredVelocity = offset.truncateLength (maxSpeed ());
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98 return desiredVelocity - velocity();
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99 }
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100
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101 bzVec2 xxxsteerForSeek (bzVec2 target) {
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102 // bzVec2 offset = target - position;
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103 bzVec2 offset = target - position;
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104 bzVec2 desiredVelocity = offset.truncateLength (maxSpeed ()); //xxxnew
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105 return desiredVelocity - velocity();
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106 }
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107
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108 // ------------------------------------------------------------------------
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109 // Obstacle Avoidance behavior
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110 //
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111 // Returns a steering force to avoid a given obstacle. The purely
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112 // lateral steering force will turn our vehicle towards a silhouette edge
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113 // of the obstacle. Avoidance is required when (1) the obstacle
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114 // intersects the vehicle's current path, (2) it is in front of the
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115 // vehicle, and (3) is within minTimeToCollision seconds of travel at the
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116 // vehicle's current velocity. Returns a zero vector value (bzVec2::zero)
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117 // when no avoidance is required.
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118 bzVec2 steerToAvoidObstacle (float minTimeToCollision, Obstacle obstacle) {
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119
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120 bzVec2 avoidance = obstacle.steerToAvoid (this, minTimeToCollision);
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121 // XXX more annotation modularity problems (assumes spherical obstacle)
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122 if (avoidance != bzVec2::zero)
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123 annotateAvoidObstacle (minTimeToCollision * speed());
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124
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125 return avoidance;
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126 }
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127
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128 // avoids all obstacles in an ObstacleGroup
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129
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130 bzVec2 steerToAvoidObstacles (float minTimeToCollision,
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131 ObstacleGroup obstacles) {
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132
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133 bzVec2 avoidance;
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134 PathIntersection nearest, next;
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135 float minDistanceToCollision = minTimeToCollision * speed();
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136
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137 next.intersect = false;
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138 nearest.intersect = false;
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139
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140 // test all obstacles for intersection with my forward axis,
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141 // select the one whose point of intersection is nearest
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142 for (ObstacleIterator o = obstacles.begin(); o != obstacles.end(); o++)
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143 {
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144 // xxx this should be a generic call on Obstacle, rather than
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145 // xxx this code which presumes the obstacle is spherical
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146 findNextIntersectionWithSphere ((SphericalObstacle)**o, next);
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147
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148 if ((nearest.intersect == false) ||
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149 ((next.intersect != false)
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150 (next.distance < nearest.distance)))
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151 nearest = next;
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152 }
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153
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154 // when a nearest intersection was found
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155 if ((nearest.intersect != false)
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156 (nearest.distance < minDistanceToCollision))
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157 {
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158 // show the corridor that was checked for collisions
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159 annotateAvoidObstacle (minDistanceToCollision);
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160
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161 // compute avoidance steering force: take offset from obstacle to me,
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162 // take the component of that which is lateral (perpendicular to my
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163 // forward direction), set length to maxForce, add a bit of forward
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164 // component (in capture the flag, we never want to slow down)
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165 bzVec2 offset = position - nearest.obstacle.center;
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166 avoidance = offset.perpendicularComponent (forward());
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167 avoidance = avoidance.normalize ();
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168 avoidance *= maxForce ();
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169 avoidance += forward() * maxForce () * 0.75;
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170 }
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171
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172 return avoidance;
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173 }
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174
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175 // ------------------------------------------------------------------------
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176 // Unaligned collision avoidance behavior: avoid colliding with other
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177 // nearby vehicles moving in unconstrained directions. Determine which
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178 // (if any) other other vehicle we would collide with first, then steers
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179 // to avoid the site of that potential collision. Returns a steering
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180 // force vector, which is zero length if there is no impending collision.
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181
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182 bzVec2 steerToAvoidNeighbors (float minTimeToCollision, AVGroup others) {
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183
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184 // first priority is to prevent immediate interpenetration
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185 bzVec2 separation = steerToAvoidCloseNeighbors (0, others);
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186 if (separation != bzVec2::zero) return separation;
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187
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188 // otherwise, go on to consider potential future collisions
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189 float steer = 0;
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190 Ship* threat = NULL;
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191
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192 // Time (in seconds) until the most immediate collision threat found
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193 // so far. Initial value is a threshold: don't look more than this
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194 // many frames into the future.
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195 float minTime = minTimeToCollision;
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196
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197 // xxx solely for annotation
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198 bzVec2 xxxThreatPositionAtNearestApproach;
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199 bzVec2 xxxOurPositionAtNearestApproach;
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200
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201 // for each of the other vehicles, determine which (if any)
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202 // pose the most immediate threat of collision.
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203 for (AVIterator i = others.begin(); i != others.end(); i++)
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204 {
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205 Ship other = **i;
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206 if (other != this)
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207 {
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208 // avoid when future positions are this close (or less)
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209 float collisionDangerThreshold = radius() * 2;
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210
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211 // predicted time until nearest approach of "this" and "other"
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212 float time = predictNearestApproachTime (other);
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213
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214 // If the time is in the future, sooner than any other
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215 // threatened collision...
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216 if ((time >= 0) (time < minTime))
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217 {
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218 // if the two will be close enough to collide,
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219 // make a note of it
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220 if (computeNearestApproachPositions (other, time)
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221 < collisionDangerThreshold)
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222 {
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223 minTime = time;
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224 threat = other;
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225 xxxThreatPositionAtNearestApproach
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226 = hisPositionAtNearestApproach;
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227 xxxOurPositionAtNearestApproach
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228 = ourPositionAtNearestApproach;
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229 }
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230 }
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231 }
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232 }
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233
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234 // if a potential collision was found, compute steering to avoid
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235 if (threat)
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236 {
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237 // parallel: +1, perpendicular: 0, anti-parallel: -1
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238 float parallelness = forward.dot(threat.forward);
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239 float angle = 0.707f;
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240
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241 if (parallelness < -angle)
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242 {
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243 // anti-parallel "head on" paths:
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244 // steer away from future threat position
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245 bzVec2 offset = xxxThreatPositionAtNearestApproach - position;
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246 float sideDot = offset.dot(side());
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247 steer = (sideDot > 0) ? -1.0f : 1.0f;
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248 }
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249 else
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250 {
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251 if (parallelness > angle)
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252 {
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253 // parallel paths: steer away from threat
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254 bzVec2 offset = threat.position - position;
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255 float sideDot = offset.dot(side());
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256 steer = (sideDot > 0) ? -1.0f : 1.0f;
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257 }
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258 else
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259 {
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260 // perpendicular paths: steer behind threat
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261 // (only the slower of the two does this)
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262 if (threat.speed() <= speed())
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263 {
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264 float sideDot = side().dot(threat.velocity);
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265 steer = (sideDot > 0) ? -1.0f : 1.0f;
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266 }
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267 }
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268 }
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269 }
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270
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271 return side() * steer;
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272 }
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273
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274 // Given two vehicles, based on their current positions and velocities,
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275 // determine the time until nearest approach
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276 float predictNearestApproachTime (Ship other) {
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277
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278 // imagine we are at the origin with no velocity,
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279 // compute the relative velocity of the other vehicle
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280 bzVec2 myVelocity = velocity;
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281 bzVec2 otherVelocity = other.velocity;
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282 bzVec2 relVelocity = otherVelocity - myVelocity;
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283 float relSpeed = relVelocity.length;
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284
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285 // for parallel paths, the vehicles will always be at the same distance,
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286 // so return 0 (aka "now") since "there is no time like the present"
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287 if (relSpeed == 0) return 0;
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288
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289 // Now consider the path of the other vehicle in this relative
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290 // space, a line defined by the relative position and velocity.
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291 // The distance from the origin (our vehicle) to that line is
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292 // the nearest approach.
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293
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294 // Take the unit tangent along the other vehicle's path
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295 bzVec2 relTangent = relVelocity / relSpeed;
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296
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297 // find distance from its path to origin (compute offset from
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298 // other to us, find length of projection onto path)
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299 bzVec2 relPosition = position - other.position;
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300 float projection = relTangent.dot(relPosition);
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301
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302 return projection / relSpeed;
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303 }
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304
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305 // Given the time until nearest approach (predictNearestApproachTime)
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306 // determine position of each vehicle at that time, and the distance
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307 // between them
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308 float computeNearestApproachPositions (Ship other, float time) {
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309
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310 bzVec2 myTravel = forward * speed * time;
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311 bzVec2 otherTravel = other.forward * other.speed * time;
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312
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313 bzVec2 myFinal = position + myTravel;
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314 bzVec2 otherFinal = other.position + otherTravel;
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315
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316 // xxx for annotation
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317 ourPositionAtNearestApproach = myFinal;
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318 hisPositionAtNearestApproach = otherFinal;
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319
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320 return bzVec2::distance (myFinal, otherFinal);
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321 }
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322
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323 // otherwise return zero
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324 return bzVec2::zero;
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325 }
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326
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327 // ------------------------------------------------------------------------
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328 // pursuit of another vehicle ( version with ceiling on prediction time)
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329
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330 bzVec2 steerForPursuit (Ship quarry) {
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331 return steerForPursuit (quarry, FLT_MAX);
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332 }
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333
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334 bzVec2 steerForPursuit (Ship quarry, float maxPredictionTime) {
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335
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336 // offset from this to quarry, that distance, unit vector toward quarry
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337 bzVec2 offset = quarry.position - position;
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338 float distance = offset.length ();
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339 bzVec2 unitOffset = offset / distance;
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340
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341 // how parallel are the paths of "this" and the quarry
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342 // (1 means parallel, 0 is pependicular, -1 is anti-parallel)
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343 float parallelness = forward.dot(quarry.forward());
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344
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345 // how "forward" is the direction to the quarry
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346 // (1 means dead ahead, 0 is directly to the side, -1 is straight back)
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347 float forwardness = forward.dot(unitOffset);
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348
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349 float directTravelTime = distance / speed;
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350 int f = intervalComparison (forwardness, -0.707f, 0.707f);
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351 int p = intervalComparison (parallelness, -0.707f, 0.707f);
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352
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353 float timeFactor = 0; // to be filled in below
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354 bzVec2 color; // to be filled in below (xxx just for debugging)
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355
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356 // Break the pursuit into nine cases, the cross product of the
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357 // quarry being [ahead, aside, or behind] us and heading
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358 // [parallel, perpendicular, or anti-parallel] to us.
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359 switch (f)
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360 {
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361 case +1:
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362 switch (p)
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363 {
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364 case +1: // ahead, parallel
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365 timeFactor = 4;
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366 color = gBlack;
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367 break;
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368 case 0: // ahead, perpendicular
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369 timeFactor = 1.8f;
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370 color = gGray50;
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371 break;
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372 case -1: // ahead, anti-parallel
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373 timeFactor = 0.85f;
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374 color = gWhite;
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375 break;
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376 }
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377 break;
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378 case 0:
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379 switch (p)
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380 {
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381 case +1: // aside, parallel
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382 timeFactor = 1;
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383 color = gRed;
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384 break;
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385 case 0: // aside, perpendicular
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386 timeFactor = 0.8f;
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387 color = gYellow;
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388 break;
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389 case -1: // aside, anti-parallel
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390 timeFactor = 4;
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391 color = gGreen;
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392 break;
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393 }
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394 break;
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395 case -1:
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396 switch (p)
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397 {
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398 case +1: // behind, parallel
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399 timeFactor = 0.5f;
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400 color= gCyan;
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401 break;
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402 case 0: // behind, perpendicular
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403 timeFactor = 2;
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404 color= gBlue;
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405 break;
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406 case -1: // behind, anti-parallel
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407 timeFactor = 2;
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408 color = gMagenta;
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409 break;
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410 }
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411 break;
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412 }
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413
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414 // estimated time until intercept of quarry
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415 float et = directTravelTime * timeFactor;
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416
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417 // xxx experiment, if kept, this limit should be an argument
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418 float etl = (et > maxPredictionTime) ? maxPredictionTime : et;
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419
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420 // estimated position of quarry at intercept
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421 bzVec2 target = quarry.predictFuturePosition (etl);
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422
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423 // annotation
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424 annotationLine (position,
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425 target,
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426 gaudyPursuitAnnotation ? color : gGray40);
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427
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428 return steerForSeek (target);
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429 }
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430
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431 // ------------------------------------------------------------------------
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432 // evasion of another vehicle
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433 bzVec2 steerForEvasion (Ship menace, float maxPredictionTime) {
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434
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435 // offset from this to menace, that distance, unit vector toward menace
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436 bzVec2 offset = menace.position - position;
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437 float distance = offset.length;
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438
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439 float roughTime = distance / menace.speed;
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440 float predictionTime = ((roughTime > maxPredictionTime) ? maxPredictionTime : roughTime);
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441 bzVec2 target = menace.predictFuturePosition (predictionTime);
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442
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443 return steerForFlee (target);
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444 }
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445
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446
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447 // ------------------------------------------------------------------------
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448 // tries to maintain a given speed, returns a maxForce-clipped steering
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449 // force along the forward/backward axis
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450 bzVec2 steerForTargetSpeed (float targetSpeed) {
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451 float mf = maxForce();
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452 float speedError = targetSpeed - speed ();
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453 return forward () * clip (speedError, -mf, +mf);
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454 }
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455
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456
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457 // ----------------------------------------------------------- utilities
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458 bool isAhead (bzVec2 target) {return isAhead (target, 0.707f);};
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459 bool isAside (bzVec2 target) {return isAside (target, 0.707f);};
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460 bool isBehind (bzVec2 target) {return isBehind (target, -0.707f);};
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461
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462 bool isAhead (bzVec2 target, float cosThreshold)
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463 {
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464 bzVec2 targetDirection = (target - position ()).normalize ();
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465 return forward().dot(targetDirection) > cosThreshold;
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466 }
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467
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468 bool isAside (bzVec2 target, float cosThreshold)
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469 {
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470 bzVec2 targetDirection = (target - position ()).normalize ();
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471 float dp = forward().dot(targetDirection);
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472 return (dp < cosThreshold) (dp > -cosThreshold);
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473 }
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474
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475 bool isBehind (bzVec2 target, float cosThreshold)
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476 {
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477 bzVec2 targetDirection = (target - position).normalize ();
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478 return forward().dot(targetDirection) < cosThreshold;
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479 }
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480 }
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