Support baking gridmap navmesh.

[lliberadzki]

Normally it's necessary to add navigation meshes under every tile nodes. One example is described in #17118. Its hard to do this inside the editor for more complex 3d shapes as there is not 3d navmesh editor included.
With this commit it would be possible to omit generating navmeshes for each tile and generate navmesh for gridmap as a whole. This would also make it possible to place obstacles or props with gridmap itself. Look at the following gif for example:

I don't know if this will be useful but i added it for personal project and thought i would share. Along with #22767 it would allow navigating procedurally generated gridmaps. What do you guys think?

Bugsquad edit: Fixes #18837.

[lliberadzki]

Fixed failing travis check.

[Xenoamor]

Very excited for this. Should also resolve the duplicate #18837

Am going to test this functionality now Looks like it's working for me

[Zylann]

Just wondering, wouldnt it be cleaner if navigation could query collision meshes from PhysicsServer rather than querying nodes? Or design an API so that we can customize the parsing?
Because otherwise we'll keep needing every node generating collision shapes using servers to intrusively be added to the recast module, while non-official modules AND GDScript plugins doing that are unable to be included. This is a problem I had for a while but it is impossible to solve cleanly at the moment.

[Xenoamor]

There's talk of overhauling how Navigation works such as in #15110, however Reduz is likely busy with the Vulkan backend work. It might be worth making a new issue to discuss what changes/additions should be made to it for 3.2 or maybe 4.0. Currently I am unaware of a single place to discuss this sort of stuff

[lliberadzki]

Querying PhysicsServer would be probably better, but you would still need to differentiate meshes you want for navigations and one you don't. So somewhat like #15110. Which is somewhat similar (at least in concept) to how Unity deals with it.
But that would probably be bigger overhaul for navigation.

[Zylann]

@lliberadzki yeah that's why I suggested there could be an API for that as well

[akien-mga]

Some comments about Navigation from @reduz on IRC:

15:23 <reduz> jfons: for 4.0 I want to move Navigation to a server, so we can add better optimizations as well as better thread support (and not depend on the Navigation node)
15:23 <reduz> jfons: this would  also allow do make the PhysicsServer directly generate and update navmeshes in real-time to the Navigation server, making it hugely more optimal
15:24 <jfons> reduz: that would be great, also adding dynamic obstacles i quite a requested feature
15:24 <reduz> yeah

In the meantime, this PR seems good, it's not a lot of code and implements a useful feature.

[akien-mga]

Thanks!

[lliberadzki]

Thanks a lot

[realkotob]

How do you set which tiles to navigate and which ones are obstacles? And which floor is the reference?

[lliberadzki]

This just passes all tiles geometry to recastnavigation baking process. This means that whatever is not reachable by agent (as for example in climbing distance, or not wide enough for agent radius) is an obstacle.