Altalena (see-saw)

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FKBox seeSaw;

float rotx = -PI / 2 + PI / 20f;

float roty = -PI / 2 - PI / 10f;

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float mouseXwhenNotPressed = width / 2;

float mouseYhenNotPressed = 0;

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void setup() {

  size(600, 600, P3D);

  //smooth();

  rectMode(CORNERS);

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  int W = color(255);

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  seeSaw = new FKBox(this, -50f, -10f, 50f, 10f, 0f, W);      

  addNode(addNode(addNode(addNode(addNode(seeSaw)))));

}

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FKBox addNode(FKBox parent) {

  FKBox aNewNode = new FKBox(this, -2f, 0, 2f, 90f, 0f, color(128));

  parent.attach(aNewNode, 0,  parent.h / 2f);

  return aNewNode;

}

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void draw() {

  background(99);

  stroke(0);

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  // Change height of the camera with mouseY

  float distZ = 575.0f;

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  float xCam = 300 + distZ * sin(rotx) * cos(roty);

  float yCam = 300 + distZ * cos(rotx);

  float zCam = distZ * sin(rotx) * sin(roty);

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  camera(xCam, yCam, zCam, // eyeX, eyeY, eyeZ

  300f, 300f, 0.0f, // centerX, centerY, centerZ

  0.0f, 1.0f, 0.0f); // upX, upY, upZ

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  // Orange point light on the right

  pointLight(150, 100, 0, // Color

  300, -150, 0); // Position

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  // Blue directional light from the left

  directionalLight(0, 102, 255, // Color

  -1, 0, 0); // The x-, y-, z-axis direction

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  // Yellow spotlight from the front

  spotLight(255, 255, 109, // Color

  400, 250, 375, // Position

  0f, -0.5f, -0.5f, // Direction

  PI, 0.1f); // Angle, concentration

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  ellipseMode(CENTER);

  ellipse(width / 2, height / 2, 80, 80);

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  translate(width / 2, height / 2);

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  strokeWeight(2);

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  if (mousePressed == false) {

    mouseXwhenNotPressed = mouseX;

    mouseYhenNotPressed = mouseY;

  }

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  if (mousePressed == false || mouseButton == LEFT) {

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    float force = (float) (mouseXwhenNotPressed) / (float) (width)

      * 0.4f - 0.2f;

    float decay = (float) (mouseYhenNotPressed) / (float) (height)

      * 0.02f + 0.01f;

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    seeSaw.impulse(force, decay);

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    float friction = 0.92f;

    seeSaw.move(friction);

  }

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  seeSaw.draw();

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}

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void mouseDragged() {

  float dy = mouseX - pmouseX;

  float dx = mouseY - pmouseY;

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  float rate = 0.008f;

  if (abs(dx) > abs(dy)) {

    rotx -= (dx) * rate;

    rotx = java.lang.Math.min(rotx, 0 - 0.01f);

    rotx = java.lang.Math.max(rotx, -PI + 0.01f);

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  } 

  else {

    roty += (dy) * rate;

  }

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}

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