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0 pointsmoron4hire5y ago0 comments

They aren't doing the particle sim in WebGL. That's the WASM part.

As an aside: there are new standards in the works for getting even the CanvasContext2D rendering off of the main thread. On an HTMLCanvasElement, you can call transferControlToOffscreen(), which will retrun an OffscreenCanvas object. That object can then be transfered to a Worker. From there, you can create the 2D rendering context (make sure you don't create any 2D contexts on that canvas in the main thread) and draw to the canvas in the worker (you can do this for WebGL contexts, as well).

All the drawing ops performed on the OffscreenCanvas will appear in the HTMLCanvasElement immediately, without having to perform a callback message from the Worker back to the main thread.

https://developer.mozilla.org/en-US/docs/Web/API/OffscreenCa...

Unfortunately, OffscreenCanvas is still in development in Firefox, only accessible behind a flag. In my testing with the feature enabled, it also seems that Mozilla hasn't implemented 2D contexts in Workers, only having the WebGL context available, which is quite annoying.

I don't know the status in Safari, but Apple has historically been very slow about implementing new features.

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stevenpetryk5y ago· 1 in thread

Yeah, I didn't know the specifics of this sim, I just wanted to clarify the advantages of WebGL for even 2D stuff.

The OffscreenCanvas thing sounds awesome! I still think it might be slower because you can't utilize shaders... but I'm sure we'll get there.

moron4hireOP5y ago

Yes, that is definitely true.

I use it for text rendering, myself. Getting text rendering working in shader code is pretty difficult and gives pretty low quality results. You have to create a glyph map for all the characters you plan to render--which also means you have to plan ahead of time what text you're going to render--and you are stuck with only one color for all of the text (there are some multicolor SDF-based systems, but they aren't very common).

So I render the text in a 2D rendering context, with all the fancy bells and whistles and support for changing fonts on the fly and colors and transformations and a sane API, in a Worker, save off an ImageBitmap object from it, transfer that ImageBitmap back to the main thread, and use it as a texture on 3D geometry.

I also use 3D contexts in Workers to do some pre-processing on textures, like converting equirectangular skymaps into rectalinear cubemaps. The worker is setup to be able to preload these images while the user is doing other things, then transfer the results when they are needed during a scene transition, so the scene transition is nearly instanteous.

j / k navigate · click thread line to collapse