//creator wisehackermonkey

//20240725

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//found a cool recusive algrotim that speeds up drawing 100x*

//also looks cool to boot!

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//CONTROLS

// + = make bigger  (key is actually "=")

// - = make smaller 

// SPACE = reset

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//inspired by amazing video 

//Another Falling Sand Game

//by 

// TimidAutomaton 

//https://www.youtube.com/watch?v=ArcHpsTXhb0

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//*idk real numbers are hard.

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let grid_current;

let grid_buffer;

const N = 100;

const SCALE = 1;

const EMPTY = 0;

const SAND = 1;

let radius = 20 ;

let MAX_CALL_DEPTH = 20;

function setup() {

  createCanvas(N, N);

  grid_current = create2DArray(N, N, EMPTY);

  grid_buffer = create2DArray(N, N, EMPTY);

  // Initialize some sand particles for demonstration

  grid_current[0][N/2] = SAND;

  grid_current[1][N/2] = SAND;

//   frameRate(15);

  background(GRAY)

  noSmooth()

  // noStroke()

}

​

function draw() {

    background(GRAY)

  grid_current = updateGridState(grid_buffer, grid_current);

  draw_pixels(SCALE, grid_current);

  fill(255, 0, 0, 0.40 * 255);

//   fill(255, 0, 0);

if( radius > 0){

  circle(mouseX, mouseY, radius * SCALE*2);

}

}

​

function create2DArray(rows, cols, initialValue) {

  let arr = [];

  for (let i = 0; i < rows; i++) {

    arr[i] = [];

    for (let j = 0; j < cols; j++) {

      arr[i][j] = initialValue;

    }

  }

  return arr;

}

​

​

function updateGridState(grid_buffer, grid_current) {

          for (let row = N - 2; row >= 0; row--) {  

    for (let col = 0; col < N; col++) {

        if (grid_current[row][col] === SAND) {

          if (grid_current[row + 1][col] === EMPTY) {

            grid_buffer[row][col] = EMPTY;

            grid_buffer[row + 1][col] = SAND;

          } else if (col > 0 && grid_current[row + 1][col] === SAND && grid_current[row + 1][col - 1] === EMPTY) {

            grid_buffer[row][col] = EMPTY;

            grid_buffer[row + 1][col - 1] = SAND;

          } else if (col > 0 && grid_current[row - 1][col] === SAND && grid_current[row - 1][col + 1] === EMPTY) {

            grid_buffer[row][col] = EMPTY;

            grid_buffer[row - 1][col + 1] = SAND;

          } else {

            grid_buffer[row][col] = grid_current[row][col];

          }

        } else {

          grid_buffer[row][col] = grid_current[row][col];

        }

      }

    }

    return grid_buffer;

  }

​

​

function keyPressed() {

    if (key === ' ') {

      grid_current = create2DArray(N, N, EMPTY);

    }

    if (key === '-') {

​

      radius--;

​

    } 

    if (key === '=') {

      radius++;

    }

  }

function mousePressed() {

    let col = floor(mouseX / SCALE);

    let row = floor(mouseY / SCALE);

    if (col >= 0 && col < N && row >= 0 && row < N) {

        grid_current[row][col] = SAND;

      setSandAtPosition(row, col);

    }

  }

  function mouseDragged() {

    let col = floor(mouseX / SCALE);

    let row = floor(mouseY / SCALE);

    if (col >= 0 && col < N && row >= 0 && row < N) {

      grid_current[row][col] = SAND;

      setSandAtPosition(row, col);

    }

  }

function setSandAtPosition(row, col) {

    // radius = 3;

    for (let i = -radius; i <= radius; i++) {

      for (let j = -radius; j <= radius; j++) {

        let newRow = row + i;

        let newCol = col + j;

        let distance = floor(sqrt(i * i + j * j)+.5)

        if (distance <= radius && newRow >= 0 && newRow < N && newCol >= 0 && newCol < N) {

          grid_current[newRow][newCol] = SAND;

        }

      }

    }

} 

​

​

let noiseScale = 0.02;

let noiseStrength = 0.5;

let noiseVal = 0;

let call_depth = 0

function draw_pixels(scale, grid) {

    let tested = Array.from({ length: grid.length }, () => Array(grid[0].length).fill(false));

    //the box test to only check the top bottom left right corners of the box

    // function box_test(rowStart, rowEnd, colStart, colEnd) {

    //  if (grid[rowStart][colStart] === 0 || grid[rowStart][colEnd - 1] === 0) {

    //      return false;

    //  }

    //  if (grid[rowEnd - 1][colStart] === 0 || grid[rowEnd - 1][colEnd - 1] === 0) {

    //      return false;

    //  }

    //  return true;

    // }

    //rewrite the tested box to test all its pixels and return false if any of them is empty

    function box_test(rowStart, rowEnd, colStart, colEnd) {

        for (let row = rowStart; row < rowEnd; row++) {

          for (let col = colStart; col < colEnd; col++) {

            if (grid[row][col] === 0) {

              return false;

            }

          }

        }

        return true;

      }

​

    function mark_tested(rowStart, rowEnd, colStart, colEnd) {

      for (let row = rowStart; row < rowEnd; row++) {

        for (let col = colStart; col < colEnd; col++) {

          tested[row][col] = true;

        }

      }

    }

    function draw_shape(rowStart, rowEnd, colStart, colEnd) {

        beginShape();

        //fill random  color

        // c = random(255)

        fill(call_depth*40,0,0)//+100, c*1.5, c/2);

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      vertex(colStart * scale, rowStart * scale);

      vertex(colEnd * scale, rowStart * scale);

      vertex(colEnd * scale, rowEnd * scale);

      vertex(colStart * scale, rowEnd * scale);

      endShape(CLOSE);

​

    }

    function recursive_draw(rowStart, rowEnd, colStart, colEnd, depth) {

      if (depth > MAX_CALL_DEPTH || rowStart >= rowEnd || colStart >= colEnd) return;

      call_depth = depth

      if (box_test(rowStart, rowEnd, colStart, colEnd)) {

        mark_tested(rowStart, rowEnd, colStart, colEnd);

        draw_shape(rowStart, rowEnd, colStart, colEnd);

      } else if (rowEnd - rowStart > 1 || colEnd - colStart > 1) {

        let midRow = Math.floor((rowStart + rowEnd) / 2);

        let midCol = Math.floor((colStart + colEnd) / 2);

        recursive_draw(rowStart, midRow, colStart, midCol, depth + 1);

        recursive_draw(rowStart, midRow, midCol, colEnd, depth + 1);

        recursive_draw(midRow, rowEnd, colStart, midCol, depth + 1);

        recursive_draw(midRow, rowEnd, midCol, colEnd, depth + 1);

      }

    }

​

    recursive_draw(0, grid.length, 0, grid[0].length, 0);

  }

​