I've made an Earth mod and recently added in texture, I've got this "seam" passing through the middle of Australia. There isn't anything in the image that should do that but maybe I didn't make it the proper way because I've got no idea what I was doing.

The tool we actually use for development isn't available because it uses features of the Unity editor, which means it can't be used without Unity, and we can't share our non-compiled code for legal reasons.

However, the artists made this Blender scene which does the same thing: https://we.tl/IScGiZiqGr 

The smoothness corresponds to the glossiness/reflectiveness of the object:

https://docs.unity3d.com/Manual/StandardShaderMaterialParameterSmoothness.html

However I don't think ES2's smoothness works exactly like Unity3D's (no transparency in the textures).

I'd recommend simply transforming your Albedo (color) texture into a dark grey (ground) & light grey (water/reflective areas) texture:

Well, thought that would be the last question but when I was putting in the smoothness texture I remembered Illum and PopGradient.
Couldn't find anything on the Illum but from the fact that it is on lava I assume it's supposed to be the intensity of the light "emitted" by the planet surface?

The PopGradient looks like it's supposed to determine the amount of the light from Pop texture based on the amount of population living at the planet but again I have no idea how to make it match the earth night map.

Here's the pop map the mod uses https://drive.google.com/file/d/1jlUYbMgcZPAplUvTPKg-wjHPkpnnnJqO/view (google drive looks like to be only normal hosting that doesn't compress the hell out of the image)

I'm not sure if the texture isn't too dark as the other PopGradients seem to largely differentiate between the water and the earth

You're right about the Illum/emissive, it represents how much the planet's surface will be lit even if it's not affected by a light source.

In the case of Lava, most of it emits light!

I think your population texture is too dark, and should also be in black & white. 

It varies a lot depending on the planet but most of the time it is much lighter:

Could you ask the artists how they made the gradual decreasing of light intensity and the name of the tool if it was done by one? I managed to combine the smoothness and light texture into something that resembles the base of the popgradient one but I'm having trouble with having the light "aura" that gradually fades away. The only thing that I could find in my software that sort of resembles it is basic blurring but that also makes it darker and uniform. I have the lights in a different layer so I can add effects to them independently.

 

Btw what is the thing you have as a profile picture on discord and steam? I just can't my eyes away from it :D.

Didn't want to start a new thread since you're already replying here. Could it be possible to assign a moon anomaly to the custom planet? Tried look for a way unique anomalies like the academy work but couldn't find anything.

And what's up with AnomalyDefinitions almost completely ignoring <PlanetFilterNot> ? The only filter that seems to work is the gas one. You can find anomalies on the academy planet which should be PlanetTypeDestroyed that is excluded on almost every anomaly, rarely you can see high/low gravity combinations and anything I add in is completely ignored.

If you feel Like I should create a new thread for this tell me and I'll delete this and move it to there (Or just move it if you can and have the time)

Could you ask the artists how they made the gradual decreasing of light intensity and the name of the tool if it was done by one?

The aura is made manually with Photoshop, there's unfortunately no magic filter for that!

I think you could eventually separate the white from the grey in a new layer and add a white drop shadow effect on it? I'm not sure it would look good though.

Btw what is the thing you have as a profile picture on discord and steam? I just can't my eyes away from it :D.

My avatar is a picture I made a while ago, based on a weird comic!

The artist, Mushbuh, is pretty neat and they're working on a super cool-looking game, Burrito Galaxy!

Could it be possible to assign a moon anomaly to the custom planet?

It is unfortunately impossible to spawn a specific anomaly on a specific planet with a mod: 

the only anomalies which always spawn on a planet (Auriga, Bilgeli & the Academy) are actually added manually via the Galaxy generation prefab, which isn't editable with a mod.

And what's up with AnomalyDefinitions almost completely ignoring <PlanetFilterNot> ?

I don't know about that, after taking a quick look at the code the PlanetFilterNot looks like it works...

It's some very obscure stuff which doesn't match our coding guidelines so I'd need much more time to look at it, but there seems to be a bug here.