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/* _____ _ __ ________ ___ *\
** / ___/(_) |/ / ___/ |__ \ Simple Mechanics Simulator 2 **
** \__ \/ / /|_/ /\__ \ __/ / copyright (c) 2011 Jakob Odersky **
** ___/ / / / / /___/ / / __/ **
** /____/_/_/ /_//____/ /____/ **
\* */
package sims.dynamics
import sims.math._
class Body(shapes0: Shape*) {
val shapes: List[Shape] = shapes0.toList
var force: Vector2D = Vector2D.Null
var torque: Double = 0.0
var linearVelocity: Vector2D = Vector2D.Null
var angularVelocity: Double = 0.0
private var _position: Vector2D =
(Vector2D.Null /: shapes)((v: Vector2D, s: Shape) => v + s.position * s.mass) / shapes.map(_.mass).sum
def position = _position
def position_=(pos: Vector2D) = {
val delta = pos - _position
_position = pos
for (s <- shapes) s.position += delta
}
private var _rotation: Double = 0.0
def rotation = _rotation
def rotation_=(r: Double) = {
val delta = _rotation - r
_rotation = r
for (s <- shapes) {
s.rotation += delta
s.position = position + (s.local.get rotate r)
}
}
var fixed = false
/**Returns the mass of this body. If the body is free, its mass is the sum of the masses of its shapes.
* If the body is fixed, its mass is infinite (`Double.PositiveInfinity`).
* @return this body's mass*/
lazy val mass: Double = if (!fixed) shapes.map(_.mass).sum else Double.PositiveInfinity
/**Returns the moment of inertia for rotations about the COM of this body.
* It is calculated using the moments of inertia of this body's shapes and the parallel axis theorem.
* If the body is fixed, its moment of inertia is infinite (`Double.PositiveInfinity`).
* @return moment of inertia for rotations about the center of mass of this body*/
lazy val inertia: Double = if (!fixed) shapes.map((s: Shape) => s.inertia + s.mass * (s.local.get dot s.local.get)).sum else Double.PositiveInfinity
/**Applies a force to the center of mass of this body.
* @param force applied force*/
def applyForce(force: Vector2D) = if (!fixed) this.force += force
/**Applies a force to a point on this body. The point is considered to be contained within this body.
* @param force applied force
* @param point position vector of the point (in world coordinates)*/
def applyForce(force: Vector2D, point: Vector2D) = if (!fixed) {this.force += force; torque += (point - position) cross force}
/**Applies a torque to the center of mass.*/
def applyTorque(torque: Double) = if (!fixed) this.torque += torque
/**Applies an impulse to the center of mass of this body.
* @param impulse applied impulse*/
def applyImpulse(impulse: Vector2D) = if (!fixed) linearVelocity += impulse / mass
/**Applies an impulse to a point on this body. The point is considered to be contained within this body.
* @param impulse applied impulse
* @param point position vector of the point (in world coordinates)*/
def applyImpulse(impulse: Vector2D, point: Vector2D) = if (!fixed) {linearVelocity += impulse / mass; angularVelocity += ((point - position) cross impulse) / inertia}
/**Applies an angular impulse to the center of mass.*/
def applyAngularImpulse(impulse: Double) = if (!fixed) angularVelocity += impulse / inertia
/**Linear velocity of the given point on this body (in world coordinates).*/
def velocityOfPoint(point: Vector2D) = linearVelocity + (angularVelocity cross (point - position))
/**Linear momentum.*/
def linearMomentum = linearVelocity * mass
for (s0 <- shapes0) {
s0.local = Some(s0.position - _position)
s0.body = this
}
def contains(point: Vector2D) = shapes.exists(_.contains(point))
def info = {
"Body@" + hashCode + "(" + this.getClass() + ")\n" +
"\tPosition: " + position + "\n" +
"\tRotation: " + rotation + "\n" +
"\tLinear velocity: " + linearVelocity + "\n" +
"\tAngular velocity: " + angularVelocity + "\n" +
"\tForce: " + force + "\n" +
"\tTorque: " + torque + "\n" +
"\tMass: " + mass + "\n" +
"\tInertia: " + inertia + "\n" +
"\tFixed: " + fixed + "\n" +
"\tShape count" + shapes.length
}
}
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