LineSystem - updating size without creating a new mesh

Questions
1

Hello,

I’m trying to update an existing line system with new data. If the underlying GPU buffer sizes are kept the same, everything works perfectly; but that is not the case when the size is different.

Please refer to the following PG: Babylon.js Playground
I draw a square shape composed of 4 segments, then I try to update it to a 6 segment shape with modified corners.

I have absolutely no clue on how to achieve this without disposing the old line system and replacing it with a newly created instance. I’d highly like to avoid this because in my application a lot of observers/observables are already watching the current instance, such that I’d rather not link everything again on each geometry update.

Thanks a lot for helping me :slight_smile:

PS: I’ve tried this Updating Vertices | Babylon.js Documentation
and the “instance” option in the CreateLineSystem method already, without success.

1 Like
2

Hello! Adding more vertices to instance is indeed not supported BABYLON | Babylon.js Documentation (babylonjs.com). If you don’t want to create a new system, maybe you can create a system with more vertices than initially needed and just update them as you go :slight_smile:

2 Likes
3

Oh it is not supported at all? That explains everything then, thank you for pointing it out :wink:
By the way, do you see a reason why? I mean I’ve done WebGL-based graphics engines, and this has never been a limitation, for instance using buffer orphaning. I’m just curious here :slight_smile:

1 Like
4

I think it’s just to avoid having to pass more vertex data to the GPU and just update what’s there :thinking: @Deltakosh is that correct?

5

Yep the goal is to be as frugal as possible. In this case we would have to rebuild the Vertex Array Object that can cause massive perf hits

1 Like