Redrawing only when needed?

[!untrue]

How I usually use Pixi is that the render loop will just keep going. Which is fine for things that are undergoing constant change and interaction, but I'm considering using Pixi for something more static... something that'll display a certain thing.... be interactive and respond when needed, but really be doing nothing most of the time. What I'm concerned about is the idle CPU usage... it uses a relatively small amount of CPU to leave the whole thing running at 60fps doing nothing, but it feels inefficient and wasteful. (As a user of an older mobile device, it really drives me nuts when I encounter a site that's inexplicably a performance pig.)

I'm just curious what other people are doing in these situations, and how you approach this. Does it make sense to exit the render loop when everything is finished updating, then have an event put us back in? Can you stop/pause Pixi itself? Or is this just more trouble than it's worth?

[ivan.popelyshev]

https://github.com/pixijs/pixi.js/wiki/v5-Custom-Application-GameLoop

As for how to detect if something was changed - we can't implement that because we value readability of PixiJS code more than that feature.

Its possible to track changes in transforms, but everything else is difficult. Usually people just set special flag if they app changes something and add "if (flag) { renderer.render(stage); } " in gameloop

[Exca]

I have a method where I have two different changes that can happen in the scene. Tweens and handlers that get run every frame.

For tweens I check if  amount of active tweens creater than 0, then it means that something is changing.

For onrender-handlers I have a custom component that allows for components to register themselves to get onrender -events and their return value will tell if something has updated.

If either tween has updated or any of the components requires rendertime, then that frame is rendered. Otherwise no render will occur.

In some cases this can be improved by splitting the scene into multiple canvases. One that gets updates rarely and one that holds the actual gameplay and is updated frequently. Though using that method is something that should be clearly thought out beforehand or you'll end up with multiple canvases to render each frame.

Having render loop stop completely is something that you shouldn't do. As calling requestanimationframe is really cheap and not worth the trouble to build a mechanic with renderloop cancellation. Easier to just skip rendering on frames that dont need it.

[ivan.popelyshev]

Yeah, I also used double-canvas and triple-canvas on slow devices, browser compositeLayers works better than webgl or 2d in that case. Thought i recommend to have only one of them as webgl..

[!untrue]

Thanks. I think I'll try to incorporate the flag idea, since I'm probably doing too much per frame anyway.