Texture seams on multi-terrain scene

[ymisofine]

When I use Gaia pro to create a world using multiple terrains (World size = custom, e.g. 2x2, 3x3 tiles) the textures at the edges of the terrains sometimes create a dark line or seam.  I've noticed if I use the unity terrain tools to smooth height between the scenes I can kind of make the seam disappear or become less noticeable.  

I did find this article on blending two terrains but couldn't get it to remove the seam (since it's a grid I can't follow the instructions exactly).  Aside from using the unity terrain tool to blend the heights I wanted to check and see if there were other techniques to getting rid of the seams?

[Bryan]

Just curious, if you paint textures on the terrain will these lines go away? 

 

[ymisofine]

Unfortunately no, if I paint over the texture (shown in first image) it does not make the seam go away.

[Bryan]

Another test can you take the texture spawner - and add a distance mask. 
Then hover over an area where you see the seams and spawn. 

[ymisofine]

I created a new texture spawner with a different texture with a distance mask and still get the same seam.

Since I've not been able to get this working and it's pretty unsightly I've actually abandoned trying to use the multi-scene method built into Gaia so it's not worth it to me to troubleshoot this anymore.  If PW is interested in reproducing it this was a 3x3 grid using the most up to date version of Gaia pro with the Synty Nature (LP) Biome using Unity 2020.3.30f1.  - Thanks

[Bryan]

Can you please open a new scene and setup through the Gaia Manager a multi-terrain setup and see if the issue still happens? 

I am wondering if somehow the terrains could not be marked as neighboring terrains. 
Which could potentially cause this issue. 
As I was not able to reproduce this issue. 
 

[ymisofine]

Sure - I started a whole new project for this, here's the steps I followed:

Imported Gaia Pro 2021 - Terrain & Scene Generator (not most up to date/3.3.9-c5) - Built in pipeline
Imported Snyty Studios - Nature Spawner Pack (most up to date)
    - Completely threw a bunch of errors and didn't feel like trying to figure out why it didn't work.  None of the assets or textures came in...but doesn't matter I can the issue anyway.
Gaia Manager 
 - Set up Project
 - Add in post processing 3.2.2 from Unity Registry
 - Upgrade from built in to URP (Not PW URP)

Gaia Manager
 - Create World
 - World Size - Custom 3x3 at 1024 Meters<--Not sure if there's another way to do multi-terrain setup.  This is how I went about it.
 - Target Platform - Desktop
 - Target Biome - Synty Nature (LP)
 - Workflow - World Designer (Random Generation)
  - Create World Designer

Gaia World Designer
 - World Shape - changed to image
 - Selected Terrain_Corrected.exr as the image (You can get it from my dropbox - https://www.dropbox.com/sh/1kzw709nqf3mr9u/AACsHzrPDahQx_9KodiNBkdva?dl=0)
 - Generate World
    - Warning for texture streaming - turned on

Selected Synty Nature (LP) Biome 
 - deselected everything but texture spawner
 - Updated Sand to use the Gaia included "POLYGON_sandyRock" texture
 - Spawned biome
 - Found the lake in north section of the island on the imported terrain and a seam runs directly south of it

*I did update my existing project where the problem originally occurred to use the latest greatest version of Gaia but that did not fix the seam issue when I created the new scene.  Also worth mentioning I'm using Unity 2020.3.30f1.

[Peter]

Hi @ymisofine thanks for the detailed instructions for reproducing the issue! With those instructions we are able to reproduce the issue now. We do not 100% know yet what causes it, but here is what we found so far:
 

• The issue is more a "dent" in the terrain geometry rather than a texture seam (this explains why painting over it did not fix it)
• This is more visible with the synty biome as with its sharp normal maps
• The issue seems only to occur when using an image in the world designer, when random stamps are used it does not seem to occur.

This explains at least why this was not found / reported yet. It seems that this might be some sort of rounding / precision issue when using a source image in the world designer. If the 3x3 @ 1024 terrains are your actual target for the scene, you could try the following workaround while we investigate further:
 

1. Add a stamper to the scene from the Advanced tab in the Gaia Manager (Tools > Stamper)
2. Use your image as stamp, while setting the stamp space to world space and the scale to x=3 y=3
   
3. Click "Flatten" to flatten all terrains
4. Click "Fit to World" and stamp

The world is still small enough so that it can be processed this way with the stamper, and this method does not produce any seams for me.