Questions on Recast-detour memory management

Questions
1

Hello,
I have a question about memory management on RecastJS from the BabylonJS/extension.
Maybe @Cedric, you are the best person to answer my questions.

I use your RescastJS on a game I develop without Babylon. The game have multiple scenes. Each scene are load individually, and are build with some procedural part.
Currently at each scene start, I create a Recast object to generate a fresh navmesh. At the end of the scenes, I use dispose() and unlink the recast object to be destroy with the garbage collector.
After I reload 12 times my level or load other, I have a OOM and rescast don’t want to be recreate.

I searched for documentations and I dug in the code but I did not find information about how to properly destroy recast and correctly free the memory.
I saw some __cache__ items in Recast that they are not free between scenes, maybe other data are also keep.

So, my questions :

  • Recast with Emscripten it is designed to be destroyed or to be use as none-destroyable singleton ?
  • If Recast can be destroyed, How to correctly free all the memory ?

Sincerely, Julien.

2

Hi @j.b and welcome to the forum

The recast plugin is meant to not be destroyed. Yes, it can be viewed as a singleton.

Without creating a crowd, do you still experience the OOM?

Do you call navmesh.destroy() once you are done witht it?

3

Hello @Cedric,
Thank you so much, with your response I understand much more what happen. At the end of my digging in the code, I had serious suspicions that I done something not right.
So no destruction and one instance of Recast, got it.

When I destroy the scene to load the next, I call Recast.navmesh.destroy() and Recast.dispose().

I tested without crowd instantiation. I have OOM again but later, about 18 reload.

At the moment, I will focus on rewriting my object management when I change scene to don’t destroy Recast.

4

If you have a small use case that still OOM, I’ll do a test on my side too.
For now, the best test I think is to keep the plugin then create/destroy a navmesh multiple times.

5

Hello @Cedric,
I remade my object management to leave the first instance of Recast alive. Now I don’t have OOM anymore. So it’s a success.

Just for my personal understanding, I did the create/destroy test that you suggested. With memory profiling, I see that the items __cache__ (Recast.Crowd.__cache__,…) fills each time I create a new navmesh and they are don’t free when I destroy the new navmesh.
How the memory in Recast is managed?
When the __cache__ items are free or reused?
Do I need to do something to tell Recast to manage its memory (other than destroying the navmesh)?

6

No, the interface is simple and enough for that. If, for some reason, even with create/destroy there is still OOM, then it’s an issue on the C++ side.

I believe Recast keeps some pre-allocated buffers for faster allocations.

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7

Understood. I will stop to be paranoid with the Recast memory.
Thank you Cedric.

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