Devlog 2 - Indoor / outdoor living
Buildings, Terrain and Navigation -
Hello everyone! Today I wanted to write a bit about my proof of concept for open world navigation using Godot 4. Navigation is one of the most complex systems in any open world game, and my decision to include buildings in the open world did not make that any less complex. I realized as I was experimenting that there were concrete reasons why the Bethesda games use instanced indoor scenes… It makes it much easier to do two things in particular: lighting and navigation. But I want something different. Loading into and out of interiors is immersion breaking for me, and puts a limit on some gameplay experiences. Assuming we can solve lighting and navigation, there’s no reason why we can’t do building interiors with no loading screens.
Lighting in my case is no big deal, because I am personally happy with the way Godot’s global illumination system interacts with both outdoor and indoor locations. Navigation on the other hand was always going to be a challenge. Each building would need it’s own navigation mesh, but how would that interact with the global terrain navigation? I am using the fantastic Terrain3D Addon for the open world, which allows you to paint navigation regions and bake them. This works great and allows for multiple navigation regions. There was still the question of the best approach for doing navigation in buildings.
My strategy
The idea is to create a navigation mesh for each building, and then use NavigationLink3D to allow for Navigation between each building and the terrain. This will allow me to create and maintain each building’s nav mesh in it’s own scene and then just worry about the link in the open world. The main downside I have discovered is that ensuring the NavigationLink works is more of an art than a science. Placing the endpoints of the link requires a fair amount of trial and error, and manual testing to make sure Navigation Agents can cross the link. This could prove to be annoying as I build towns that require me to manually test many links, so there could be room for improvement in that respect. Not a whole lot of information exists online about NavigationLink, so it’s entirely possible that I am missing something.
I encourage you to read through the documentation page for NavigationLink3D that I linked above. Essentially what it does is provide a “bridge” between Navigation Regions.
Here is a gif of one of my NPCs walking into a building (and crossing Navigation Regions through the link). He even opens the door for himself :)
Just a short one here, but hope it was useful!