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/*
* Simple Mechanics Simulator (SiMS)
* copyright (c) 2009 Jakob Odersky
* made available under the MIT License
*/
package sims.dynamics
import sims.geometry._
import sims.collision._
import sims.dynamics.joints._
import scala.collection.mutable._
/**A world contains and simulates a system of rigid bodies and joints.*/
class World {
/**Time intervals in which this world simulates.*/
var timeStep: Double = 1.0 / 60
/**Number of constraint corrections per time step.*/
var iterations: Int = 10
/**Gravity in this world.*/
var gravity = Vector2D(0, -9.81)
/**Bodies contained in this world.*/
val bodies = new ArrayBuffer[Body]
/**Joints contained in this world.*/
val joints = new ArrayBuffer[Joint]
/**Monitoring methods for bodies.
* <p>
* The first element of the tuple is the method's title and the second the method.
* Example usage: monitors += ("Y-Position", _.pos.y.toString)
* This will calculate all bodies - whose <code>monitor</code> field is set to
* <code>true</code> - second position components.*/
val monitors = new ArrayBuffer[(String, Body => String)]
/**Collsion detector who manages collision detection in this world.*/
val detector: Detector = new GridDetector(this)
/**Warning if a body's velocity exceeds the speed of light.*/
var overCWarning = false
/**Flag to enable collision detection.*/
var enableCollisionDetection = true
/**Flag to enable position correction for constraints.*/
var enablePositionCorrection = true
/**Minimal, non-zero linear velocity.*/
var minLinearVelocity: Double = 0.0001
/**Minimal, non-zero angular velocity.*/
var minAngularVelocity: Double = 0.0001
/**Returns all shapes of all bodies in this world.*/
def shapes = for (b <- bodies; s <- b.shapes) yield s
/**Adds the given body to this world.*/
def +=(body: Body) = bodies += body
/**Adds the given joint to this world.*/
def +=(joint: Joint): Unit = joints += joint
/**Adds the given prefabricated system of bodies and joints to this world.*/
def +=(p: prefabs.Prefab): Unit = {
for (b <- p.bodies) this += b
for (j <- p.joints) this += j
}
/**Adds the given sequence of bodies to this world.*/
def ++=(bs: Seq[Body]): Unit = for(b <- bs) this += b
/**Removes the given body from this world.*/
def -=(body: Body): Unit = bodies -= body
/**Removes the given joint from this world.*/
def -=(joint: Joint): Unit = joints -= joint
/**Removes the given prefabricated system of bodies and joints from this world.*/
def -=(p: prefabs.Prefab): Unit = {
for (b <- p.bodies) this -= b
for (j <- p.joints) this -= j
}
/**Removes the given sequence of bodies from this world.*/
def --=(bs: Seq[Body]) = for(b <- bs) this -= b
/**Removes all bodies, joints and monitoring methods from this world.*/
def clear() = {joints.clear(); bodies.clear(); monitors.clear()}
/**Current time in this world.*/
var time: Double = 0.0
/**Simulates a time step of the duration <code>timeStep</code>.
* <p>
* The time step is simulated in the following phases:
* <ol>
* <li>Forces are applied to bodies.</li>
* <li>Accelerations are integrated.</li>
* <li>Velocities are corrected.</li>
* <li>Velocities are integrated.</li>
* <li>Postions are corrected.</li>
* <li>The method <code>postStep()</code> is executed.</li>
* </ol>*/
def step() = {
time += timeStep
//force applying objects
for (j <- joints) j match {case f: ForceJoint => f.applyForce; case _ => ()}
//integration of acclerations, yields velocities
for (b <- bodies) {
val m = b.mass
b.applyForce(gravity * b.mass)
val a = b.force / b.mass
val alpha = b.torque / b.I
b.linearVelocity = b.linearVelocity + a * timeStep
b.angularVelocity = b.angularVelocity + alpha * timeStep
}
//correction of velocities
for (i <- 0 until iterations){
for(c <- joints) c.correctVelocity(timeStep)
if (enableCollisionDetection) for (c <- detector.collisions) c.correctVelocity(timeStep)
}
//integration of velocities, yields positions
for (b <- bodies) {
//warning when body gets faster than speed of light
if (b.linearVelocity.length >= 300000000) overCWarning = true
if (b.linearVelocity.length < minLinearVelocity) b.linearVelocity = Vector2D.Null
if (b.angularVelocity.abs < minAngularVelocity) b.angularVelocity = 0.0
b.pos = b.pos + b.linearVelocity * timeStep
b.rotation = b.rotation + b.angularVelocity * timeStep
b.force = Vector2D.Null
b.torque = 0.0
}
//correction of positions
if (enablePositionCorrection) for (i <- 0 until iterations){
for (c <- joints) c.correctPosition(timeStep)
if (enableCollisionDetection) for (c <- detector.collisions) c.correctPosition(timeStep)
}
postStep()
}
/**Initially empty method that is executed after each time step. This method
* may be overriden to create custom behaviour in a world.*/
def postStep() = {}
/**Returns information about this world.*/
def info = {
"Bodies = " + bodies.length + "\n" +
"Shapes = " + shapes.length + "\n" +
"Joints = " + joints.length + "\n" +
"Collisions = " + detector.collisions.length + "\n" +
"Monitors = " + monitors.length + "\n" +
"Gravity = " + gravity + "m/s^2\n" +
"Timestep = " + timeStep + "s\n" +
"Time = " + time + "s\n" +
"Iterations = " + iterations
}
}
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