This one work but only with triangles:

var allcorners = [], allcornersAvailable = []; var secondBlocked = false; var lastSecond = 0; var minuteBlocked = false; var p1, p2, p3; var triangleobj; var r, g, b; var newPoint;

function setup() { createCanvas(windowWidth, windowHeight); allcorners.push(createVector(0, 0)); allcorners.push(createVector(width, 0)); allcorners.push(createVector(width, height)); allcorners.push(createVector(0, height));

noStroke(); }

function draw() { background(255);

if(second() == 0 && minuteBlocked == false) { minuteBlocked = true; allcorners.push(createVector(random(width), random(height))); }

if(second() != 0 && minuteBlocked == true) { minuteBlocked = false; }

if(second() != lastSecond && secondBlocked == false) { allcornersAvailable = allcorners.slice();

var rand1 = floor(random(allcornersAvailable.length));
p1 = allcornersAvailable[rand1];
allcornersAvailable.splice(rand1, 1);

var rand2 = floor(random(allcornersAvailable.length));
p2 = allcornersAvailable[rand2];
allcornersAvailable.splice(rand2, 1);

var rand3 = floor(random(allcornersAvailable.length));
p3 = allcornersAvailable[rand3];
allcornersAvailable.splice(rand3, 1);

secondBlocked = true;
lastSecond = second();

r = random(255);
g = random(255);
b = random(255);

console.log("H:" + hour() + ", M:" + minute() + ", S:" + second());

}

if(second() != lastSecond && secondBlocked == true) { secondBlocked = false; }

fill(r, g, b); triangle(p1.x, p1.y, p2.x, p2.y, p3.x, p3.y);

}