Hi everyone,

I’m currently working on a replacement mesh mod for the taxi cab from the base game and I’ve run into an issue with the surface shading.

I’ve spent a lot of time on the mesh, but I’m struggling to get a perfectly smooth look on the larger panels like the hood and the roof. Even though everything looks fine in the editor, the moment I import it into the game, visible shading breaks appear exactly where the UV seams are. It’s like the light doesn’t flow continuously across the different UV islands, different panels of the car got darker/lighter on diffent conditions

I’ve tried a few things to fix it:
-Used Weighted Normals and Data Transfer in Blender to smooth things out.
-Checked face orientation.
-Tried different export settings, but the "seams" are still catching the light in a way that looks unnatural.
-Used Wesley Howe Milkshape plugin to realign normals

But nothing of this helps. I probably messed things up during the proccess, plus this mesh is not mine. I really don't want to start everything from the begining because it took me weeks to make it at this stage. I even paid for this model LOL

I’m really trying to finish this project properly and I know people will love it, so any advice or help would be a lifesaver.

Thanks!

Could potentially be the Normal Map texture - if any sections of the UV overlap, or they aren't all oriented in the same direction, you can get inconsistent lighting in those areas.
Can also happen if you're using a 'blank' normal map - as these don't behave like not having one at all, they behave like 'try to light these surfaces like they're flat'.

An example, if you unwrapped a cube and separated the faces on the UV, stacked some of them in the same location, and rotated or flipped others - it would look fine on the diffuse texture and the mesh normals would still be correct, but once you generated a normal map for that texture it would be inaccurate. For 2D lighting information to be continuous, the UVs also must be.

For what it's worth, I'd take a look at your second screenshot of your replacer next to EA's ghost taxi abomination and be a little more forgiving of your work :P
Shooting for the stars and landing among the clouds is okay! You can always come back to it in a later update.

I didn't edited the ghost taxi in any way! These texture anomalies started since I have imported my mod in game (maybe some textures are linked between them idk).

Actually some of the islands on my UV map are really oriented in different direction (never thought this could be an issue). My normal map is not actually blank - it's solid gray with 30% opacity (doing the same as some car creators from which I have mods from), but never thought that was so important.

I'm looking to fix my normal map and to put the UV islands to point in the right direction.

Thanks for the advice!

Edit 1: I've rearranged the UV to be like this (in the screenshot below). The previous was way too chaotic

Edit 2: Edited the normal map to be with same color and level of transparency as the OG map. Converted it into DDS format with DXT5 encoding/compression (to enable the alpha channel), and it's working. Also applied "Allign normals" where the UV seems are to smooth out sharp edges (with Wesley Howe's Milkshape tool).

Thank you again @CardinalSims for enlighten me and helping me fix the issue!