The tilemap is just a FlxTilemapExt. Nothing fancy there.
I could grab tiles nearby entities. What I wonder is how the stamp would work. Not sure if there's a way to get the sprite of any given tilemap ? Plus, as you correctly pointed out, I'm afraid that the stamping would go outside the boundaries of said tiles. And yes, this is the purpose of the rectangles, to mask the stamps.
I might place all those rectangles manually, but sounds like a brute forced solution. I was wondering how other people might solve this, but sounds like isn't a easy task. Many thanks @jcox171 for your replies so far :)
On plain Openfl, using 2D on Canvas and not webGL I'm getting great performances (60+ fps) even on a pretty old PC. WebGL performances varied a lot in time, and on different browsers too: Chrome with webGL was terrible a few months ago, but now it seems to be more or less aligned to the other browsers like Firefox, at least with our projects.
2D on webGL is good too, but the "feeling" is different, you have to try yourself, maybe it depends on the hardware and the different antialiasing.
I don't know how much worse can be the performances using Flixel above Openfl, I still have to start using it ;)
Ah! Don't forget that Canvas supports a lot more blendmodes than WebGL currently!