# How to troubleshoot CreateScreenshot "hanging"?

**URL:** <https://forum.babylonjs.com/t/how-to-troubleshoot-createscreenshot-hanging/58290>\
**Category:** Questions\
**Tags:** screenshot\
**Created:** [May 7, 2025, 7:17am UTC](https://forum.babylonjs.com/t/how-to-troubleshoot-createscreenshot-hanging/58290 "2025-05-07T07:17:15Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![Tom\_Haddon](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/tom_haddon/32/2189_2.png) [@Tom\_Haddon](https://forum.babylonjs.com/u/Tom_Haddon)\
**Post date:** [May 7, 2025, 7:17am UTC](https://forum.babylonjs.com/t/how-to-troubleshoot-createscreenshot-hanging/58290/1 "2025-05-07T07:17:15Z")

</div>

Hi Folks,

I’m trying to create a page that generates a number of screenshots for me. I want to do this by creating a bunch of cameras in an array, and then adding an `onReadyObservable` that iterates through them and generates the screenshots.

I’ve got a playground page [https://playground.babylonjs.com/#1YQBZO#1](https://playground.babylonjs.com/#1YQBZO#1) that does what I want.

The problem I have is that in my local branch `BABYLON.Tools.CreateScreenshotUsingRenderTargetAsync` seems to just hang. I’ve tried wrapping it in a `try`/`catch` but no error seems to be thrown either. Adding `console.log` statements I can see that it’s getting to the line before that and then not getting any further.

Here’s the code snippet I have locally:

```auto
      scene.onReadyObservable.add(async () => {
        for (i = 0; i < POICameraArray.length; i++){
          console.log(i);
          POICameraArray[i].attachControl(canvas, false);
          scene.activeCamera = POICameraArray[i];
          scene.render();
          console.log("Scene rendered");
          try {
            console.log("About to try");
            const data = await BABYLON.Tools.CreateScreenshotUsingRenderTargetAsync(
              engine,
              scene.activeCamera,
              {width: 1000, height: 1000, precision: 2.0, finalWidth: 1000, finalHeight: 1000}
            );
            console.log("Screenshotted");
          } catch (error){
            console.log(error);
          }
          console.log(data);
        }
      });

```

All I see in the console is `0`, `Scene rendered` and then `About to try`. If I replace the CreateScreenshot call with something harmless like an async function that logs “Hello” to a console that seems to work fine. And obviously it works fine in the playground.

Any ideas how I’d troubleshoot this?

Thanks, Tom

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<div class="post-metadata">

**Author:** ![Joe\_Kerr](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/joe_kerr/32/39017_2.png) [@Joe\_Kerr](https://forum.babylonjs.com/u/Joe_Kerr)\
**Post date:** [May 7, 2025, 8:01am UTC](https://forum.babylonjs.com/t/how-to-troubleshoot-createscreenshot-hanging/58290/2 "2025-05-07T08:01:14Z")

</div>

Seems like the promise hangs. Can you put a “debugger” before CreateScreenshotUsingRenderTargetAsync and step through until it stops? Maybe this could give some clues.

Other than that: double check parameters to CreateScreenshotUsingRenderTargetAsync. Double check camera array. Does a camera need to be ready? If you assign an active camera, will this be active immediately or does it need a frame to be set up? Right when the callback to scene.onReadyObservable starts, can you wait 2 or so seconds to ensure the scene is really ready? Try any of the other Screenshot functions?

* * *

[Looking at the source](https://github.com/BabylonJS/Babylon.js/blob/472cd97a1ad2fd2612adb0e3e66b97edc7467dd1/packages/dev/core/src/Misc/screenshotTools.ts#L237)

- Try en-/disabling antialiasing (the parameter)?
- Switch between WebGL and WebGPU?

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<div class="post-metadata">

**Author:** ![Tom\_Haddon](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/tom_haddon/32/2189_2.png) [@Tom\_Haddon](https://forum.babylonjs.com/u/Tom_Haddon)\
**Post date:** [May 7, 2025, 10:02am UTC](https://forum.babylonjs.com/t/how-to-troubleshoot-createscreenshot-hanging/58290/3 "2025-05-07T10:02:48Z")

</div>

I’ve tried adding a debugger and stepping through the code. It seems to get “all the way through” eventually but then just goes back to not doing anything (presumably still waiting for the promise to return?).

I’ve triple checked the parameters and they seem fine, I’ve also tried `CreateScreenshotAsync` but that also has the same effect.

I’ve also tried adding a 2 second wait at various points but that doesn’t seem to help either ☹

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<div class="post-metadata">

**Author:** ![labris](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/labris/32/12576_2.png) [@labris](https://forum.babylonjs.com/u/labris)\
**Post date:** [May 7, 2025, 10:28am UTC](https://forum.babylonjs.com/t/how-to-troubleshoot-createscreenshot-hanging/58290/4 "2025-05-07T10:28:50Z")

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Note that the line `scene.render();` doesn’t have any effect on the result - [https://playground.babylonjs.com/#1YQBZO#2](https://playground.babylonjs.com/#1YQBZO#2)

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<div class="post-metadata">

**Author:** ![Tom\_Haddon](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/tom_haddon/32/2189_2.png) [@Tom\_Haddon](https://forum.babylonjs.com/u/Tom_Haddon)\
**Post date:** [May 7, 2025, 11:38am UTC](https://forum.babylonjs.com/t/how-to-troubleshoot-createscreenshot-hanging/58290/5 "2025-05-07T11:38:46Z")

</div>

I’ve downloaded babylon.max.js from the cdn and am using that locally so I can make modifications to try and pinpoint what’s happening. I can see that the `renderWhenReady` function is firing (see [Babylon.js/packages/dev/core/src/Misc/screenshotTools.ts at 472cd97a1ad2fd2612adb0e3e66b97edc7467dd1 · BabylonJS/Babylon.js · GitHub](https://github.com/BabylonJS/Babylon.js/blob/472cd97a1ad2fd2612adb0e3e66b97edc7467dd1/packages/dev/core/src/Misc/screenshotTools.ts#L329)) at which point `texture.isReadyForRendering()` and `camera.isReady(true)` are both `true`. I can also see that `scene.render()` (see [Babylon.js/packages/dev/core/src/Misc/screenshotTools.ts at 472cd97a1ad2fd2612adb0e3e66b97edc7467dd1 · BabylonJS/Babylon.js · GitHub](https://github.com/BabylonJS/Babylon.js/blob/472cd97a1ad2fd2612adb0e3e66b97edc7467dd1/packages/dev/core/src/Misc/screenshotTools.ts#L381)) is being fired.

I don’t quite understand all the code here, but I think `engine.onEndFrameObservable.addOnce` might not be being fired (if I add a `console.log` statement before `if (finalWidth === width && finalHeight === height) {` I don’t see it). Could that be the problem?

If I add a console.log statement at the end of the `finally` after the scene is rendered, I see that logged (see [Babylon.js/packages/dev/core/src/Misc/screenshotTools.ts at 472cd97a1ad2fd2612adb0e3e66b97edc7467dd1 · BabylonJS/Babylon.js · GitHub](https://github.com/BabylonJS/Babylon.js/blob/472cd97a1ad2fd2612adb0e3e66b97edc7467dd1/packages/dev/core/src/Misc/screenshotTools.ts#L400)) and if I check the list of `engine.onEndFrameObservable` I do see the one added from line 333 of the code, so it looks like the engine is never finishing the current frame per [Babylon.js docs](https://doc.babylonjs.com/typedoc/classes/BABYLON.AbstractEngine#onendframeobservable).

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<div class="post-metadata">

**Author:** ![Evgeni\_Popov](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/evgeni_popov/32/4432_2.png) [@Evgeni\_Popov](https://forum.babylonjs.com/u/Evgeni_Popov)\
**Post date:** [May 7, 2025, 2:22pm UTC](https://forum.babylonjs.com/t/how-to-troubleshoot-createscreenshot-hanging/58290/6 "2025-05-07T14:22:02Z")

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> [@Tom\_Haddon](#):
>
> don’t quite understand all the code here, but I think `engine.onEndFrameObservable.addOnce` might not be being fired

For `onEndFrameObservable` to be fired, you must setup a render loop (`engine.runRenderLoop(...)`). Maybe you don’t have one?

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<div class="post-metadata">

**Author:** ![Tom\_Haddon](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/tom_haddon/32/2189_2.png) [@Tom\_Haddon](https://forum.babylonjs.com/u/Tom_Haddon)\
**Post date:** [May 7, 2025, 2:45pm UTC](https://forum.babylonjs.com/t/how-to-troubleshoot-createscreenshot-hanging/58290/7 "2025-05-07T14:45:27Z")

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Er, yeah, that was it! Thanks!