Failed Shadertoy “Dust” Game – Browsers Need To Compile Shaders Off the Main Thread!

I was working on a Dust Game on shadertoy for a few weeks and got a decent amount of the way through it. Unfortunately I hit a snag.

There’s a sad fact that browsers compile WebGL shaders on the main thread. If ever WebGL blocks for too long, browsers consider WebGL hung and reports to the user that WebGL crashed.

The shaders for my game got complex enough that they were hitting the timeout while compiling, even though I wasn’t even close to being finished. So, I simplified a bit and published it unfinished, thinking that perhaps when WebGL 2.0 comes out this summer, I can revisit it.

Unfortunately, but totally understandably, different people have different machines in the wild, and some people have computers that take longer to compile shaders than my computer does, which means that plenty of people were still “crashing”. Because of this, the shadertoy people moved my shader back to draft/private until I simplified it more since crashes are no good, even if they are not realy real crashes in the normal sense. You can still see it by direct link here if you are interested: Shadertoy: Dust Sim Sandbox (Incomplete)

I’ve spent enough time on this thing so I’m going to leave it private for now, but I really think this shows a fundamental problem with WebGL.

Since the shaders compile on the main thread (apparently in many browsers if not all!), and detect a crash/hang by timing out, it means that when you write WebGL code, you really have to either keep things super simple in your shaders, or you have to be ok with having some amount of users experiencing “crashes” when the shader compiles time out on their machine.

In other words, you have to choose between innovation and stability.

That doesn’t really bode well for a platform like WebGL that basically is all about innovation! I’m sure this same problem plagues WebVR, which means that if you want to make a WebVR experience that works well on all machines, you better not do anything very complex 😛

Despite this failure, I did succeed in making a minesweeper game though, check it out here: Shadertoy: Minesweeper

Anyways, onto the next next shadertoy! I think I’m going to try to make one of those side view physics based car/motorcycle/bicycle hill climbing games.


It turns out my understanding of the shader compiling process was a bit simplified. Read the link below for the full scoop, but in the end, the problem remains, because there doesn’t seem to be any way to query the status of the async work, so you seem to have to guess and hope you have enough work to do. In the case of shadertoy, there is no geometry to load, or things of that nature, so that makes it especially difficult to deal with.

Asynchronous Shader Compilation

Thanks to @tuan_kuranes for the better information (:



About Demofox

I'm a game and engine programmer at Blizzard Entertainment and have been making games since 1990 (starting out with QBasic and TI-85 games) My shipped titles include: * Heroes of the Storm * StarCraft II: Heart of the Swarm & Legacy of the void * Insanely Twisted Shadow Planet (PC) * Gotham City Impostors (PC, 360, PS3) * Line Rider (PC, Wii, DS) I also like hiking, making music, learning cool new stuff and attempting the impossible.