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j public void movedouble dt public void draw jx

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Unformatted text preview: ouble dvdv = dvx*dvx + dvy*dvy; double drdr = dx*dx + dy*dy; double sigma = this.radius + that.radius; double d = (dvdr*dvdr) - dvdv * (drdr - sigma*sigma); if (d < 0) return INFINITY; return -(dvdr + Math.sqrt(d)) / dvdv; } 50 Collision system: event-driven simulation main loop two particles on a collision course Initialization. ・Fill PQ with all potential particle-wall collisions. ・Fill PQ with all potential particle-particle collisions. no collision third particle interferes: no collision “potential” since collision may not happen if some other collision intervenes An invalidated event public void bounceOff(Particle that) { double dx = that.rx - this.rx, dy = that.ry - this.ry; double dvx = that.vx - this.vx, dvy = that.vy - this.vy; double dvdr = dx*dvx + dy*dvy; double dist = this.radius + that.radius; double J = 2 * this.mass * that.mass * dvdr / ((this.mass + that.mass) * dist); double Jx = J * dx / dist; double Jy = J * dy / dist; this.vx += Jx / this.mass; this.vy += Jy / this.mass; that.vx -= Jx / that.mass; that.vy -= Jy / that.mass; this.count++; Important note: This is high-school physics, so we won’t be testing you on it! that.count++; } Main loop. ・Delete the impending event from PQ (min priority = t). ・If the event has been invalidated, ignore it. ・Advance all particles to time t, on a straight-line trajectory. ・Update the velocities of the colliding particle(s). ・Predict future particle-wall and particle-particle collisions involving the colliding particle(s) and insert events onto PQ. 51 52 Event data type Collision system implementation: skeleton Conventions. ・ ・One particle null ・Both particles null public class CollisionSystem { private MinPQ<Event> pq; private double t = 0.0; private Particle particles; Neither particle null ⇒ particle-particle collision. ⇒ particle-wall collision. ⇒ redraw event. // the priority queue // simulation clock time // the array of particles public CollisionSystem(Particle particles) {...
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