p5.j​​s 使用变量改变大小

Question

I want to know how to change the size/location of an object in p5 using an infinite loop. for some reason, this doesn't work

function setup() {
  createCanvas(400, 400);
}
var size=80

function draw() {
  noFill();
    ellipseMode(CENTER);
    rectMode(CENTER);
  background(220);
  ellipse(40,40,size);
rect(40, 40, size, size);
  
}
test()
function test()
{
  size=size+1
  draw()
  setTimeout(test, 200)
}

How do i do it?

Also, here's the error message:

p5.js says: There's an error due to "noFill" not being defined in the current scope (on line 77 in about:srcdoc [about:srcdoc:77:3]).

If you have defined it in your code, you should check its scope, spelling, and letter-casing (JavaScript is case-sensitive). For more: https://p5js.org/examples/data-variable-scope.html https://developer.mozilla.org/docs/Web/JavaScript/Reference/Errors/Not_Defined#What_went_wrong Did you just try to use p5.js's noFill() function? If so, you may want to move it into your sketch's setup() function.

For more details, see: https://github.com/processing/p5.js/wiki/p5.js-overview#why-cant-i-assign-variables-using-p5-functions-and-variables-before-setup

Answer 1

The reason why you're getting the error is because the you're calling draw() before noFill , ellipse , rectMode ... etc are defined, which seems to happen after your javascript. You can verify this by replacing test() with setTimeout(test) , which shouldn't have that error because it should run the code after the p5 functions are defined.

In any case, as Samathingamajig says, you generally shouldn't call draw by yourself-- p5 automatically does it, defaulting to aiming to call it 60 times a second. You can just fix your code by deleting the draw() line.

Here's a working snippet:

 function setup() { createCanvas(400, 400); } var size=80 function draw() { noFill(); ellipseMode(CENTER); rectMode(CENTER); background(220); ellipse(40,40,size); rect(40, 40, size, size); } test() function test() { size=size+1 setTimeout(test, 200) }

 <script src="https://unpkg.com/p5@1.1.9/lib/p5.min.js"></script>

Answer 2

Generally functions like rectMode and ellipseMode are called in the setup function. Here is what your code should look like:

function setup() {
  createCanvas(400, 400);
  ellipseMode(CENTER);
  rectMode(CENTER);
}
var size = 80

function draw() {
  background(220);
  rect(40, 40, size, size);
  ellipse(40, 40, size);
  noFill();
}