Performance - draw vs redraw

Processing Coding Questions
1

when would it be good to use draw() and when would it be good to use redraw()

and could a program ran via a main draw() loop be made faster by only using a redraw-when-needed approach?

if so, is redraw, in a while(true) { redraw(); } faster than just letting the draw loop run?

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2

is redraw, in a while(true) { redraw(); } faster than just letting the draw loop run?

In one sense, since while(true) { redraw(); } run at an unbounded rate, whereas draw() runs at a rate targeting frameRate. On the other hand, will it run the contents of draw() any faster? I don’t think so.

Generally, go for the noLoop() + redraw() approach if you’re generating a still image.

If you need to redraw sometimes, drawing into a separate PGraphics cache is probably the best approach – draw it with image() every frame but only update (draw into) it when you need to.

3

i intend to draw every frame but only if i actually need to draw, for example, a 2 FPS (eg 500 MS draw delay) spinning cube vs a 60FPS spinning cube

4

Ok, something like this then:

if (frameCount % 30 == 0) {
    updatePGraphics();
}
drawPGraphics();
5

i meant like…

if one graphics object is updating at 60FPS and another at 2 FPS then would draw() always be called every frame due to the 60 FPS updating graphics object?

6

No, it isn’t faster, because it doesn’t run at all. redraw() doesn’t do what you think it does. It doesn’t call draw() – it sets a flag so that handleDraw will later fire draw once – even if noLoop is set – and clear the flag.

So, if you endlessly call redraw(), all you are doing is setting the same flag over and over, freezing the sketch. Try it.

void draw() {
  background(128);
  text(frameRate, width/2,height/2);
}

void mouseReleased() {
  while(true) { redraw(); }
}
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