p5.js Web Editor | Verlet-physics-playground

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let objects = [];
let sticks = [];
const sim_steps = 8;
var gravity = null;
const friction = 0.999;
let mouseMode = "add_objects";
let paused = false;
const addStickState = {
  o: null,
};
const moveState = {
  o: null,
}
​
function setup() {
  createCanvas(600, 600);
  gravity = createVector(0, 0.001);
  noStroke();
  
  createButton("Pause/unpause")
    .mousePressed(() => {
      paused = !paused;
    });
  createButton("Add objects")
    .mousePressed(() => mouseMode = "add_objects");
  createButton("Add sticks")
    .mousePressed(() => mouseMode = "add_sticks");
  createButton("Pin/unpin object")
    .mousePressed(() => mouseMode = "pin_object");
  createButton("Move object")
    .mousePressed(() => mouseMode = "move_object");
  createButton("Delete object")
    .mousePressed(() => mouseMode = "delete_object");
  createButton("Clear all")
    .mousePressed(() => mouseMode = "clear");
}
​
function draw() {
  background(32);
  stroke(0);
  fill(192);
  circle(width / 2, height / 2, width);
  
  if (!paused) {
  const dt = 25 / sim_steps;
    for (i = 0; i < sim_steps; i++) {
      applyGravity(objects);
      updatePositions(objects, dt);
      applyConstraints(objects);
      handleCollisions(objects);
      updateSticks(sticks, dt);
    }
  }
  
  drawSticks(sticks);
  drawObjects(objects);
  
  if (addStickState.o) {
    fill("white");
    stroke("orange");
    strokeWeight(2);
    circle(addStickState.o.pos.x, addStickState.o.pos.y, addStickState.o.radius * 2);
    strokeWeight(1);
  }
  
  if (moveState.o) {
    fill("white");
    stroke("magenta");
    strokeWeight(2);
    circle(moveState.o.pos.x, moveState.o.pos.y, moveState.o.radius * 2);
    strokeWeight(1);
  }
  
  let strMode = "";
  switch (mouseMode) {
    case "add_objects":
      strMode = "Click to add new objects";
      break;
    case "add_sticks":
      strMode = "Click an object, then another to add a stick between them";
      break;
    case "pin_object":
      strMode = "Click an object to pin/unpin it";
      break;
    case "move_object":
      strMode = "Click an object to start moving it, click again to stop";
      break;
    case "delete_object":
      strMode = "Click an object to delete it";
      break;
  }
  noStroke();
  fill(192, 192, 64);
  text(`${objects.length} objects, ${sticks.length} sticks`, 5, 15);
  fill(64, 192, 64);
  text(strMode, 5, 30);
  
  if (paused) {
    fill(192, 64, 64);
    text("--- PAUSED ---", 5, 45);
  }
}
​
function mouseInCanvas() {
  return mouseX >= 0 && mouseX <= width && mouseY >= 0 && mouseY <= height;
}
​
function mouseClicked() {
  switch (mouseMode) {
    case "add_objects":
      if (mouseInCanvas()) {
        objects.push(
          new VerletObject(
            createVector(mouseX, mouseY),
            10,
            random(["red", "green", "blue", "cyan", "magenta", "yellow", "pink", "purple", "orange"]),
            false
          )
        );  
      }
      break;
    case "add_sticks":
      if (mouseInCanvas()) {
        const o = objectFromPoint(mouseX, mouseY);
        if (addStickState.o && o) {
          sticks.push(
            new Stick(
              addStickState.o,
              o,
              p5.Vector.sub(o.pos, addStickState.o.pos).mag()
            )
          );
          addStickState.o = null;
        } else {
          addStickState.o = o;
        }
      }
      break;
    case "pin_object":
      if (mouseInCanvas()) {
        const o = objectFromPoint(mouseX, mouseY);
        if (o) {
          o.pinned = !o.pinned;
          if (!o.pinned) {
            o.prev_pos.x = o.pos.x;
            o.prev_pos.y = o.pos.y;
            o.accel.x = 0;
            o.accel.y = 0;
          }
        }
      }
      break;
    case "move_object":
      if (mouseInCanvas()) {
        if (moveState.o) {
          moveState.o = null;
        } else {
          const o = objectFromPoint(mouseX, mouseY);
          if (o) {
            moveState.o = o;
          }
        }
      }
      break;
    case "delete_object":
      if (mouseInCanvas()) {
        const o = objectFromPoint(mouseX, mouseY);
        if (o) {
          objects = objects.filter((object) =>
            object !== o
          );
          sticks = sticks.filter((stick) =>
            stick.o1 !== o && stick.o2 !== o
          );
        }
      }
      break;
    case "clear":
      if (confirm("Are you sure you want to delete all objects?")) {
        objects = [];
        sticks = [];
      }
  }
}
​
function mouseMoved() {
  if (moveState.o) {
    moveState.o.pos.x = mouseX;
    moveState.o.pos.y = mouseY;
    moveState.o.prev_pos.x = mouseX;
    moveState.o.prev_pos.y = mouseY;
  }
}
​
function objectFromPoint(x, y) {
  for (let idx in objects) {
    const o = objects[idx];
    if (
      x >= o.pos.x - o.radius
      && x <= o.pos.x + o.radius
      && y >= o.pos.y - o.radius
      && y <= o.pos.y + o.radius
    ) {
      return o;
    }
  }
  return null;
}
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