objects-and-simulations/day3/libs/teilchen/examples/LessonX05_AngleConstraints/LessonX05_AngleConstraints.pde

import mathematik.*;

import teilchen.Particle;
import teilchen.Physics;
import teilchen.constraint.AngleConstraintStick;
import teilchen.constraint.Stick;
import teilchen.force.AngleConstraintSpring;
import teilchen.force.Gravity;
import teilchen.force.Spring;
import teilchen.force.ViscousDrag;
import teilchen.integration.RungeKutta;


Physics mPhysics;

Particle mParticleA;

Particle mParticleB;

Particle mParticleC;

Particle mParticleD;

AngleConstraintSpring mAngleConstraintABC;

AngleConstraintStick mAngleConstraintBCD;

void setup() {
  size(640, 480);
  frameRate(30);
  smooth();

  mPhysics = new Physics();
  mPhysics.setInegratorRef(new RungeKutta());

  ViscousDrag myViscousDrag = new ViscousDrag();
  myViscousDrag.coefficient = 1f;
  mPhysics.add(myViscousDrag);

  Gravity myGravity = new Gravity();
  myGravity.force().y = 50;
  mPhysics.add(myGravity);

  /* particles */
  mParticleA = mPhysics.makeParticle();
  mParticleB = mPhysics.makeParticle();
  mParticleC = mPhysics.makeParticle();
  mParticleD = mPhysics.makeParticle();

  mParticleA.position().set(width / 2 + 50, height / 3);
  mParticleB.position().set(width / 2, height - height / 1.75f);
  mParticleC.position().set(width / 2, height - height / 4);
  mParticleD.position().set(width / 2, height - height / 8);

  mParticleA.radius(7);
  mParticleB.radius(3);
  mParticleC.radius(10);
  mParticleD.radius(2);

  mParticleB.fixed(true);

  /* springs */
  Spring mSpringAB = new Spring(mParticleA, mParticleB);
  mSpringAB.strength(250);
  mSpringAB.damping(10);
  mPhysics.add(mSpringAB);

  Spring mSpringBC = new Spring(mParticleB, mParticleC);
  mSpringBC.strength(250);
  mSpringBC.damping(10);
  mPhysics.add(mSpringBC);

  Stick mSpringCD = new Stick(mParticleC, mParticleD);
  mSpringCD.damping(1);
  mPhysics.add(mSpringCD);

  /* angle constraint */
  mAngleConstraintABC = new AngleConstraintSpring(mParticleA, mParticleB, mParticleC);
  mAngleConstraintABC.min_angle(PI * 0.5f);
  mAngleConstraintABC.damping(1);
  mAngleConstraintABC.strength(200);
  mPhysics.add(mAngleConstraintABC);

  mAngleConstraintBCD = new AngleConstraintStick(mParticleB, mParticleC, mParticleD);
  mAngleConstraintBCD.min_angle(PI * 0.8f);
  mAngleConstraintBCD.damping(0.5f);
  mPhysics.add(mAngleConstraintBCD);
}

void draw() {
  /* attach particle to mouse */
  if (mousePressed) {
    mParticleA.position().set(mouseX, mouseY);
  }

  /* apply constraints */
  mAngleConstraintABC.pre_step();
  mAngleConstraintBCD.pre_step();
  draw_physics();

  mPhysics.step(1f / frameRate);

  /* remove contraints */
  mAngleConstraintABC.post_step();
  mAngleConstraintBCD.post_step();
}

void draw_physics() {
  background(255);

  drawSprings();
  drawSticks();
  drawParticles();
}

void drawSprings() {
  for (int i = 0; i < mPhysics.forces().size(); i++) {
    if (mPhysics.forces(i) instanceof Spring) {
      final Spring mSpring = (Spring)mPhysics.forces(i);
      if (mSpring instanceof AngleConstraintSpring) {
        strokeWeight(1);
        if (mSpring.active()) {
          stroke(255, 0, 0, 64);
        } 
        else {
          stroke(255, 0, 0, 16);
        }
      } 
      else {
        strokeWeight(3);
        stroke(0, 128);
      }
      line(mSpring.a(), mSpring.b());
    }
  }
  strokeWeight(1);
}

void drawSticks() {
  for (int i = 0; i < mPhysics.constraints().size(); i++) {
    if (mPhysics.constraints(i) instanceof Stick) {
      final Stick mStick = (Stick)mPhysics.constraints(i);
      if (mStick instanceof AngleConstraintStick) {
        strokeWeight(1);
        if (mStick.active()) {
          stroke(0, 127, 255, 64);
        } 
        else {
          stroke(0, 127, 255, 16);
        }
      } 
      else {
        strokeWeight(3);
        stroke(0, 128);
      }
      line(mStick.a(), mStick.b());
    }
  }
  strokeWeight(1);
}

void drawParticles() {
  stroke(0);
  fill(92);
  drawParticle(mParticleA);
  fill(127);
  drawParticle(mParticleB);
  fill(192);
  drawParticle(mParticleC);
  fill(64);
  drawParticle(mParticleD);
}

void drawParticle(Particle p) {
  ellipse(p.position().x, 
  p.position().y, 
  p.radius() * 2, p.radius() * 2);
}

void line(Particle p1, Particle p2) {
  line(p1.position().x, p1.position().y, 
  p2.position().x, p2.position().y);
}