Dramatic increase in WebGPU startup time (whenReady)

Tutorials and tips
1

Hi everyone,

Thought I’d share this to potentially save you some headaches. :face_with_head_bandage:

I have been migrating from WebGL to WebGPU and encountered a massive increase :collision: in my game startup time. From a default timing report I already got the culprit: scene.executeWhenReady

But why? I had just ported all shaders to wgsl and there should not have been any glsl-to-wgsl transpiling stuff going on (which is slow).

What nailed was this debug code :

export default function Override(BABYLON, win) {
  BABYLON.Scene.prototype.isReady = function(checkRenderTargets = true) { ... }
  BABYLON.Engine.prototype.areAllEffectsReady = function() { ... }
  
  //e.g.
  BABYLON.WebGPUEngine.prototype.areAllEffectsReady = function() {
    for (const key in this._compiledEffects) {
      const effect = this._compiledEffects[key];

      if (!effect.isReady()) {
        if(typeof effect.name === "string") report("effects:"+effect.name)
        else report("effects:"+effect.name.fragment+"/"+effect.name.vertex);
        return false;
      }
    }

    return true;   
  }
}

This way you know what is taking so long in executeWhenReady.You log a debug message (or whatever) whenever any of the function is about to return false / set return var to false. I do this per call, so that I will get a sorted history. And there I got the perpetrator: weaponSwingTrail nodeMaterial :open_mouth:

Since it is a node material it does not live in the shaders directory and so I missed to port it. The moment I set material.shaderLanguage = Engine.ShaderLanguage.WGSL, startup time was on par with WebGL.

Phew, I was about to rage quite a ditch WebGPU :grin:

Best wishes
Joe

**Don’t forget to turn off the debug code :face_with_crossed_out_eyes:

4 Likes
2

cc @Evgeni_Popov (please be patient he is on vacation:))

3

Uhm, wait. The post was meant to be a tip. Did not want to complain about Babylon or anything :face_with_peeking_eye: I guess the tl;dr is: look for leftover GLSL shaders if your WebGPU startup time is comparably higher.

Yay Evgeni :beach_with_umbrella: :tropical_drink: :smiley:

1 Like
4

Good catch. The slow startup was caused by one missed node material (weaponswingTrail) still using the wrong shader setup. Setting it to WGSL fixed the issue and restored normal performance.