BASIC TRACK – Pattern Grids with Loops + Random()

Goal: Use nested for loops to draw a grid and add variation with random() for color, size, or shape.

Learn to see how repetition and chance interact to create visual rhythm.

Starter Code

// Session 3 — Grid + Random
// Goal: Use for loops and random() to make a colorful grid

let rows;
let columns;
let h;
let size;
let seed;

function setup() {
  createCanvas(400, 400);
  colorMode(HSB);
  noStroke();

  // setup variables
  rows = 10;
  columns = 10;
  size = 40;
  seed = 10;   // change this number for a new pattern
  
  background(0, 0, 95);

  randomSeed(seed);  // same pattern every draw

  // nested loops = repetition across rows and columns
  for (let x = 0; x < columns; x = x + 1) {
    for (let y = 0; y < rows; y = y + 1) {

      // choose a random hue and shape size
      h = random(0, 360);
      size = random(20, 40);

      // set fill color using HSB
      fill(h, 100, 100);

      // alternate shapes using even/odd logic
      if (x % 2 == 0) {
        ellipse(x * 40 + 20, y * 40 + 20, size);
      } else {
        rect(x * 40 + 20, y * 40 + 20, size);
      }
    }
  }
}

Requirements

• Use two for loops to create a grid pattern.
• Incorporate random() for color and either size or shape.
• Include two different shapes (e.g., circle, rect, triangle).
• Keep code organized and comment your choices.

Extensions

• Add randomSeed() to lock the pattern or remove it for fresh output each run.
• Create checkerboard logic (if ((i + j) % 2 === 0)) to switch shapes.
• Try fill(random(360), 80, 90) for full spectrum variation.
• Replace circle() with triangle() or arc() to explore new geometry.

Reflection Questions

1. How did you use for loops to structure your pattern?
2. What variables control color and size variation?
3. How does changing the random seed affect your composition?
4. What happens if you swap random() for a fixed value?