Skyrim's Horizon Mesh and ENB's and the challenge of fixing it.

[Kuldebar]

Many of us who play Skyrim with an ENB will have noticed at one time or another a really ugly line, sometimes quite defined other times very smudgy, but a line nonetheless, that marks the distant horizon in the game in areas where you can see at a great distance.

 

Both JawZ, who knows a bit about the inner workings of lighting, ENB and Skyrim and Ramccoid, who has done a number of mods involving textures and meshes for Skyrim, have worked on the issue in the past and more recently. Unfortunately both fell short of total success in solving the problem:

 

 

Ramccoid:

 

The Sky Line or Ripple Bug is not actually a bug, it's the side effect of having colours in the sky. Colours that produce dramatic sunsets, etc., these are called colour bands and are the culprit for the lines you see when examining the sky.
The only way to remove these and give a clear lineless sky, are simply to remove the colour and that is basically what this mod does. So if you like really dramatic coloured dusks and dawns then this isn't for you.

 

JawZ:

 

If you were to apply a grey color to all vertices you would lose the ENB sky separation which is Horizon, Middle and Top intensity and curve.
I have already made such a version way back when I first released my atmosphere.nif edited mesh but as it proved to limit the functionality of any ENB preset I decided not to release it. It will also remove the separation of sky sections inside the Creation Kit/default game rendering as well.

For best compatibility on how the game engine as well as ENB is setup it's best to leave the original vertex coloring intact.
Red = Horizon
Green = Middle Sky
Blue = Top sky

And then just optimize it either through "just" making the color ordering better or add in more vertices to better control the blend between the primary colors.

 

Reason for me not uploading a greyscaled or one colored atmosphere.nif was also because of limiting the amount of users complaining about the removal of the Sky sections (even if I would have 3 options then and explain in detail the difference between, not the first time that happens sadly) but such a mesh allows for a far better color banding control and would suite screenarchers very well I would think.

 

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So, in summary, as it stands right now, the best way to deal with the Skyline/Horizon Mesh Issue according to JawZ...is to avoid exacerbating it by keeping the "original vertex coloring intact". This sounds like good advice but far too many presets out there don't handle the colors accordingly so you end up with some really ugly distant skylines.

 

 

 

 

 

 

 

 

Edited June 2, 2014 by Kuldebar

[Aiyen]

Edit: Since the first version of this post was not really super clear I decided to just update it so it is a bit more clear. 

 

 

Line: Caused because the gameworld is a halfsphere put down on top of a square. 

Limited solutions: Alter the half spherical sky box mesh, and ENB mist feature: 

 

Mesh issues: Stuff will start to look a bit stretched the more you do it, and it will not be able to eliminate the issue everywhere since the gameworld is square not circular... so there will always be those certain areas where you can see this. 

 

Mist: Will only slightly hide the issue.... the intensities of the effect might not look good on certain weather types. But you can get far using it. 

 

Mixing the two is most likely the best option if someone wants to go all out. 

 

 

 

Banding: Caused due to limited amount of bits in the color channels. This is the same effect you will see if you compare 8bit with 16 and 32bit colors.

 

(Limited) solutions: Animated saturated random noise, dithering, adaptation, general tonemapping. 

 

Noise: This helps smooth the tones out by making sure most pixels do not get so huge differences that the effect becomes visible. The downside is that there will always be a slight grainy look, this can however also be minimized. 

 

Dithering: In my experience not nearly as effective as noise, but it does help a little bit, so if you only have small amounts of banding then some dithering code can be quite worth it. 

 

Adaptation-tonemapping: Adjusting your tonemapping so that the color variation is limited enough that the issue never become visible. During dawn and dusk when you have adaptation then the tone variations are at their most extreme, hence getting entirely rid of the effect during those periods is rather difficult. 

 

The reason I put limited in () is that.. you can remove the effect entirely if you make it so that your dynamic range is always within the threshold of when the issue happens.. since there is always going to be a point where the issue will become apparent since ultimately the cause is that the color information required to make sure it does not is not available.  

[Kuldebar]

Awesome information and clarification and elaboration, Aiyen, thanks!

 

Here's a screenie I took a few moments ago in Ivarstead it early evening:

 

 

This location makes it really easy to observe the horizon line.

[Aiyen]

Just did a rewrite of the previous post so it was more clear! Hope that helped making it more understandable. 

[phryxolydian]

When I first came to the forums I think I did a topic about this same issue along with other questions. I don't actually remember who was the one who helped me (was it you Aiyen?) but it really improved my game a lot. Here's a not so recent image with the improved horizon:

 

 

Before, it used to be a very noticeable black bar without any fading whatsoever. Believe me, this is much better!

[JawZ]

The horizon with it's issue can't be totally fixed. Once the Skyrim fog line is removed by Sky mesh/atmosphere.nif edits you are still left with fugly looking waterplanes that makes a very defined line similar to the line between the horizon and water planes, the area removed by my mesh, so far I do not know of any way of fixing this other than to make the distance fog to be colored as the fog and/or use ENB Mist functions to blend that part better.

 

Oh Kuldebar when I say vertex color should be intact I mean the assigned vertex point in the mesh not the sections viewed in game. For a good smooth transitions between the Horizon, Middle and Top sky you need to tweak the Intensity and Curve values.

[redirishlord]

I haven't seen a post from/for JawZ's new sky mesh, which is available on his ENB forums ELE page  along with the latest release of ELE. Sounds like it might supersede his comment above, I just downloaded at look forward to some clear weather in Skyrim to give it a thorough examination.