iOS: noticeable stutter & frame drop with complex models when touching screen

[jonklein]

Describe the bug
When rendering a somewhat complex scene, touch start and end events trigger a noticeable stutter or frame drop, even if there is no touch handler configured.

To Reproduce
Steps to reproduce the behavior:

1. With the Playground app in this repo, load a more complex model than the default (https://raw.githubusercontent.com/KhronosGroup/glTF-Sample-Models/master/2.0/2CylinderEngine/glTF/2CylinderEngine.gltf"
2. Disabled the included touch handing just to ensure it's not related (comment out the call to deviceSourceManager.onDevice)
3. Run the sample, touch the screen rapidly.
4. Framerate drops from 60 fps down to 10 fps or below depending on how quickly you tap.

Expected behavior
The rendering should not stutter or drop frame when touches start and end, particularly if there is no user processing.
Other

• Platform: iOS

edited to add Most noticeable on device, as opposed to simulator.

[CedricGuillemet]

Related : BabylonJS/BabylonNative#1047

[CedricGuillemet]

Some picking is done when a touch occurs. To avoid it, add this to your JS code:

scene.pointerUpPredicate = ()=> false;
scene.pointerDownPredicate = ()=> false;
scene.pointerMovePredicate = ()=> false;

[jonklein]

Thank you - I can confirm this prevents the stutter. As you mentioned in the other issue, it might be good to not have this enabled by default.

[bghgary]

Keeping open to discuss with Babylon.js team to see if we can somehow disable picking by default.

[PolygonalSun]

@PolygonalSun self-tag