Sean Harding - Marching Squares

 -------------------------------------

  A contribution to Daniel Shiffman's

     "Coding in the Cabana" series

  This implementation of the Marching

   Squares  algorithm  uses  inverse

    interpolation  to  help  smooth

         out   the   contours.

   The  simulation  is  interactive!

   Use  the  left  mouse  button  to

  remove material and the right mouse

   button to add material, and watch

   the contours update in real time!

 *************************************/

​

var field = [];

const cellWidth = 24;

const cellHeight = 24;

var rows, columns, marchingSquares;

​

function setup() {

  createCanvas(768, 768);

  fill(255, 204, 153);

  rows = floor(width / cellWidth);

  columns = floor(height / cellHeight);

  // initialize the array

  for (var i = 0; i <= columns; i++) {

    field.push([]);

    for (var j = 0; j <= rows; j++) {

      field[i].push(random(-1, 1));

    }

  }

  marchingSquares = new MarchingSquares(field, cellWidth, cellHeight);

}

​

function draw() {

  background(0, 51, 102);

  const mouseCellX = round(mouseX / cellWidth);

  const mouseCellY = round(mouseY / cellHeight);

  if (mouseIsPressed && mouseCellX > 0 && mouseCellX < columns && mouseCellY > 0 && mouseCellY < rows) {

    switch (mouseButton) {

      case LEFT: {

        field[mouseCellX - 1][mouseCellY - 1] -= 0.001 * deltaTime;

        field[mouseCellX + 0][mouseCellY - 1] -= 0.002 * deltaTime;

        field[mouseCellX + 1][mouseCellY - 1] -= 0.001 * deltaTime;

        field[mouseCellX - 1][mouseCellY + 0] -= 0.002 * deltaTime;

        field[mouseCellX + 0][mouseCellY + 0] -= 0.004 * deltaTime;

        field[mouseCellX + 1][mouseCellY + 0] -= 0.002 * deltaTime;

        field[mouseCellX - 1][mouseCellY + 1] -= 0.001 * deltaTime;

        field[mouseCellX + 0][mouseCellY + 1] -= 0.002 * deltaTime;

        field[mouseCellX + 1][mouseCellY + 1] -= 0.001 * deltaTime;

        break;

      }

      case RIGHT: {

        field[mouseCellX - 1][mouseCellY - 1] += 0.001 * deltaTime;

        field[mouseCellX + 0][mouseCellY - 1] += 0.002 * deltaTime;

        field[mouseCellX + 1][mouseCellY - 1] += 0.001 * deltaTime;

        field[mouseCellX - 1][mouseCellY + 0] += 0.002 * deltaTime;

        field[mouseCellX + 0][mouseCellY + 0] += 0.004 * deltaTime;

        field[mouseCellX + 1][mouseCellY + 0] += 0.002 * deltaTime;

        field[mouseCellX - 1][mouseCellY + 1] += 0.001 * deltaTime;

        field[mouseCellX + 0][mouseCellY + 1] += 0.002 * deltaTime;

        field[mouseCellX + 1][mouseCellY + 1] += 0.001 * deltaTime;

        break;

      }

    }

  }

  noStroke();

  ellipse(mouseX, mouseY, cellWidth * 3, cellHeight * 3)

  // draw the points

  strokeWeight(8);

  for (var i = 0; i <= columns; i++) {

    for (var j = 0; j <= rows; j++) {

      stroke(map(field[i][j], -1, 1, 0, 256));

      point(i * cellWidth, j * cellHeight);

    }

  }

  stroke(255);

  strokeWeight(1);

  // Go!

  marchingSquares.march(0);

}