Edit: my English in this post is awful. Written on my Phone so please don't bother
I will try to explain it but I have no real knowledge if this is correct, sorry!
First: try the values again, but let the mip_lod_bias on ZERO! And don't forget the Split values!
What is LOD (-bias)?
If you create anything in a game you have to do LODs or you will get every GPU to it's knees.
That means you say "if the car in front of you is 0-20 meters away, take the full texture", "if the car is 20-100 meters away, take this, a bit crappier texture (and polygons etc)".
So you get different "Levels Of Detail" and tell them when to use which.
"common > assettocorsa> system > cfg > "ig_config.ini" - this has some interesting settings:
"shadow_map_splits" settings that I think improve shadow draw distances.
- currently set to: SHADOW_MAP_SPLITS=0, 150.0, 500.0, 1000.0 "
These settings put the "splits" for the different LODs further away from you. So you will have "better shadows" even in further distance.
It eliminates this cutting detail line in front of you.
Additional info: perfect LODs are reached when you don't see it
What is the Shadow Map Size?
The shadow map size is how big the FIRST texture of you LODs will be. I don't know what is big and what is not but the highest inGame setting is 4096, high is 2048.
On 1920x1080 I can tell the difference. Especially when you are in the pits and look at the shadow under the roof of the garages you see the artifacts in the shadows. It should be a straight, dark line but it's these... strange looking strobe things
If you raise the map size this should go away, because the shadow calculation has "more points". It's heavy on the GPU!
For 4k you have to render everything in a higher resolution, sadly the AC shadows seem to need be raised separate. In theory you would need 4x the value of fullHD, so 4096*4= 16384.
I would say: f*ck it and type this value in, look at the shadows if it's better, I really have no clue
But you will only get 1-20fps
What are the shadow mip bias?
Again, I have no correct knowledge of this, but it's how I understand it:
The shadow mip bias is how detailed the SPLITS are. The lower the value, the more detail!
As linked to my long post before, if you have too much details in a too little area, the "pixels will start to crawl" because the "details can't decide on which pixel they should be displayed".
That problem can be solved but heavy Anti Aliasing like 8x SGSSAA.
You can imagine the SGSSAA like a discussion with the details, how they should be displayed and that will stop the crawling/aliasing/flickering. That's why it's so heavy on the GPU. MSAA only "discusses with solid objects".
Let the MIP_LOD_BIAS=0. The sharper (lod-bias on negative values sharps through more details = more flicker!) a imagine, the more flicker! Some people like it, I clearly don't! (But SGSSAA blurrs a bit so I put LITTLE sharpen through SweetFX, the LOD_BIAS sharps on a render level, SweetFX is a post effect!
So the map bias: you put every LOD to 1.0 so you won't get any detailed shadows, but they also WON'T CHANGE IN DISTANCE.
In the end, you will have just "grey areas" that are smooth and don't flicker.
In my understanding that would cancel out the higher shadow map size but again: I have no real knowledge :/
My final 2 cents:
Raise the map size, put the map bias(es) to 1.0 and increase the split distance values.
For me this gives me a smooooth experience on FullHD with 4x SGSSAA.
