Need some help with Vertex Normals and ITMs

[drewbster]

I'm making a couple mods to add more lighting to the cities, and in one of them I keep getting Identical to Masters that TES4Edit won't clean, so Wrye Bash notes it as dirty. I'm not very proficient with either program so I might be missing something (and I have BOSS but no idea how to use it, or if it'd even help here), but when I look at the mod's records in TES4Edit, I find that the IDs Wrye says are dirty are for landscape edits. Specifically:

 

> I'll add a new streetlamp

> make minor terrain adjustments to the height and/or texture and save the mod

> close CK and clean the mod with TES4 (apply filter, remove ITMs, Undelete/Disable, save on exit)

> check it in Wrye, and there's still 1 ITM

> load TES4Edit again and check the ID that Wrye gives, and see that the vertex height and/or texture were changed, but the normal wasn't

 

I've made several little terrain changes, some fine and some not, and I'll even see a record that's fine right next to one with an ITM -- and every time, the ITM is an unchanged vertex normal. I should add that I don't know exactly what a vertex normal is, I get the gist but not enough to understand why it'd change with some edits and not others.

 

I don't really care while it's for my own use, but if I decide to share these mods, I'd really like to find out what's causing these ITMs and why TES4Edit won't remove them (my guess is that it's related to being the terrain rather than something like a placeable object). Does this sound at all familiar to anyone?

[DrakeTheDragon]

Well, vertex normals, like face normals, are vectors pointing perpendicularly away from the surface, defining where's above and where's under the surface, and in case of vertex normals, that is normals at the corners, not necessarily perpendicular anymore, can create a rounded or smoothed out shape.

If for each polygon the vertex normals are perpendicular, it will create a rough edge where the polygons edges connect. If the vertex normals of each of the connecting polygons line-up at the connecting vertex though, it will create a smooth edge. And then there's in-between, by the normals not completely overlapping but still straying away some less than for a rough/hard edge.

 

In other words, normal vectors are primarily used for lighting calculations, creating either a hard edge, soft edge/smooth surface, or in-between.

https://docs.microsoft.com/en-us/windows/desktop/direct3d9/face-and-vertex-normal-vectors

 

I don't know when exactly, or how, the CS landscape editor recalculates the normals, but it's not unthinkable a normal won't change, if you just move the vertex up some or down, if it's configured to always keep the middle angle between the edges.

I also didn't know the vertex positions and vertex normals are stored separately for landscape editing, so even if you definitely "moved" the vertex around, i.e. changed it, its normal vector might still be considered an ITM. But so's GameBryo I guess.

And I could very well imagine TES4Edit can't remove these, as both, vertex position + normal, are stored as 1 record, the landscape vertex. You can either have both or none. And removing the change to the vertex' position to get rid of the unchanged vertex normal vector is out of the question.

[drewbster]

Thanks for the response. I knew normals had something to do with the lighting, now I better understand *how*.

 

After some more examination, turns out the ITMs were also in adjacent cells. Sometimes the cell was obviously close enough to have been affected, but sometimes it wasn't; either way, I found that if I went back and made a deliberate terrain height change in the problem cell, the ITM went away. So for now, I'm just backing up before any terrain edit so I can decide whether or not adjusting for a new ITM would make sense, like if it's done right on the cell borders, to avoid touching unrelated cells as much as possible.

 

[e] Update: After making terrain height modifications and cleaning the mod, I load it in Wyre Bash, then right-click "Mod Cleaning > Scan for dirty edits" to see the remaining ITMs. I reload it in TES4Edit, search for the problem records, copy the master's VHGT record and paste it for the mod's, clean again, and that clears things up. I found that in this instance, the VNML-Vertex Normals are the same, VHGT-Vertext Height Map are not, and it's always the last three pairs of digits that differ.

 

I was also having trouble actually editing those records until I tried F2 after multiple attempts at making sense of the program's EditTips.txt file.

Edited November 7, 2018 by drewbster