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Diffstat (limited to 'src/main/scala/sims/dynamics/Body.scala')
| -rw-r--r-- | src/main/scala/sims/dynamics/Body.scala | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/src/main/scala/sims/dynamics/Body.scala b/src/main/scala/sims/dynamics/Body.scala new file mode 100644 index 0000000..8c0e2ee --- /dev/null +++ b/src/main/scala/sims/dynamics/Body.scala @@ -0,0 +1,141 @@ + +/* + * Simple Mechanics Simulator (SiMS) + * copyright (c) 2009 Jakob Odersky + * made available under the MIT License +*/ + +package sims.dynamics + +import sims.geometry._ +import sims.dynamics.joints._ + +/**A two dimensional rigid body is made out of shapes. + * @param shps shapes that belong to this body.*/ +class Body(shps: Shape*){ + + /**Unique identification number.*/ + val uid = Body.nextUid + + /**Shapes that belong to this body.*/ + val shapes: List[Shape] = shps.toList + + //Shapes are added during initialisation. + for (s <- shapes) { + s.body = this + s.refLocalPos = s.pos - pos + s.rotation0 = s.rotation + } + + private var isFixed: Boolean = false + + /**Returns whether this body is fixed or not.*/ + def fixed = isFixed + + /**Fixes or frees this body. By fixing, linear and angular velocities are set to zero.*/ + def fixed_=(value: Boolean) = { + if (value) {linearVelocity = Vector2D.Null; angularVelocity = 0.0} + isFixed = value + } + + /**Flag for a world to monitor the properties of this body. + * @see World#monitors*/ + var monitor: Boolean = false + + /**Returns the position of this body. The position is equivalent to the center of mass. + * @return position of this body*/ + def pos: Vector2D = // COM = sum(pos*mass)/M + (Vector2D.Null /: shapes)((v: Vector2D, s: Shape) => v + s.pos * s.mass) / + (0.0 /: shapes)((i: Double, s: Shape) => i + s.mass) + + /**Sets the position of this body. By doing so all its shapes are translated. + * @param newPos new position*/ + def pos_=(newPos: Vector2D) = { + val stepPos = pos + shapes.foreach((s: Shape) => s.pos = s.pos - stepPos + newPos) + } + + /**Contains the current rotation of this body.*/ + private var _rotation: Double = 0.0 + + /**Returns the current rotation of this body.*/ + def rotation: Double = _rotation + + /**Sets the rotation of this body. Position and rotation of shapes are modified accordingly. + * @param r new rotation*/ + def rotation_=(newRotation: Double) = { + _rotation = newRotation + val stepPos = pos + for (s <- shapes) { + s.rotation = newRotation + s.rotation0 + s.pos = stepPos + (s.refLocalPos rotate (newRotation)) + } + } + + /**Linear velocity of this body.*/ + var linearVelocity: Vector2D = Vector2D.Null + + /**Angular velocity of this body.*/ + var angularVelocity: Double = 0 + + /**Linear velocity of the given point on this body (in world coordinates).*/ + def velocityOfPoint(point: Vector2D) = linearVelocity + ((point - pos).leftNormal * angularVelocity) + + /**Resulting force on the COM of this body.*/ + var force: Vector2D = Vector2D.Null + + /**Resulting torque on this body.*/ + var torque: Double = 0 + + /**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 (<code>Double.PositiveInfinity</code>). + * @return this body's mass*/ + def mass: Double = if (fixed) Double.PositiveInfinity else (0.0 /: shapes)((i: Double, s: Shape) => i + s.mass) + + /**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 (<code>Double.PositiveInfinity</code>). + * @return moment of inertia for rotations about the COM of this body*/ + def I: Double = if (fixed) Double.PositiveInfinity else + (0.0 /: (for (s <- shapes) yield (s.I + s.mass * ((s.pos - pos) dot (s.pos - pos)))))(_+_) + + /**Applies a force to the COM 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. Warning: 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 - pos) cross force} + + /**Applies an impulse to the COM 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. Warning: 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 - pos) cross impulse) / I} + + /**Checks if the point <code>point</code> is contained in this body.*/ + def contains(point: Vector2D) = shapes.exists(_.contains(point)) + + override def toString: String = { + "Body" + uid + " " + shapes + " fixed=" + fixed + " m=" + mass + " I=" + I + " pos=" + pos + " rot=" + rotation + " v=" + linearVelocity + " w=" + angularVelocity + " F=" + force + " tau=" + torque + } + + /**Creates a new body containing this body's shapes and the shape <code>s</code>. + * @param s new shape + * @return new body*/ + def ~(s: Shape) = new Body((s :: shapes): _*) + + /**Creates a new body containing this body's shapes and the shapes of another body <code>b</code>. + * @param b body with extra shapes + * @return new body*/ + def ~(b: Body) = new Body((this.shapes ::: b.shapes): _*) +} + +object Body { + private var uidCounter = -1 + private def nextUid = {uidCounter += 1; uidCounter} +}
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