Extra polygons in Gothic1 's WORLD.ZEN ?

[jfregnault]

Among all the .ZEN files in Gothic1 or Gothic2, one seems to contain extra (unwanted) polygons : WORLD.ZEN in Gothic1.
To be clear, when I dump all the "World.Mesh.Polygons" in a .X file (yes I know it's outdated) in order to display a scene in a 3D-renderer, it works fine for all the scenes except this one, which contains many unwanted extra polygons.
NB: when I call the "World" constructor, I pass the correct "GameVersion.Gothic1" for this ZEN file.

Example at the beginning of the game, after leaving the pond you have to follow the path:
The raw result (with all polys) : the path is blocked:

And after removing inappropriate polys, the correct terrain was hidden behind:

My approach may be too simple, yet it works for all other .ZENs !
Maybe this scene is a particular case which is not fully handled by ZenKit/ZenKitCS ?

[lmichaelis]

Hi @jfregnault , this looks like a common LOD issue. The world mesh cannot be used on its own and the BSP-tree needs to be taken into account as well.

Basically, to just show the most detailed version of the mesh, only those polygons of the mesh which fall into a BSP-tree leaf node must be considered. I will look for an example of how to do this later today and post it here.

[lmichaelis]

I apologize, I can't actually find sample C# code for you right now. The relevant section of C++ code is this:

https://github.com/GothicKit/ZenKit/blob/c8e562cb184180efd35d80559543d064514281f5/src/Mesh.cc#L193-L225

In C#, you would do something similar, specifically: Only include polygons in the output mesh which appear in BspTree.LeafPolygonIndices (may contain duplicates). You also need to exclude polygons with the IsPortal, IsGhostOccluder and IsOutdoor flags.

In addition to removing those polygons, this function also does triangulation (which you might not need to do).

[jfregnault]

Hi Luis, thank you for your so quick and clear answer ! It's likely that I have merged the LOD polygons into the "normal" terrain !
I'll check this as soon as possible, and will let you know.
Regards

[jfregnault]

You were right, it was a "common LOD issue" as you said :)
Not all polygons from "World.Mesh.Polygons" must be drawn, not even those from "World.BspTree.PolygonIndices", but starting from "World.BspTree.LeafPolygonIndices" finally gives the right result (after restricting to unique indices in order to avoid redondant content).
Thanks again