PSA uGridsToLoad limits

[SKKmods]

Messing about on a totally vanilla base game with large uGrids to use the Commonwealth for a long range shooting project with non hitscan projectiles, found some interesting things.

 

Basic ratios:

 

Fallout4Prefs.ini

[General]

uGridsToLoad = X

uExteriorCellBuffer = (uGridsToLoad+1)^2

iPreloadSizeLimit = (uGridsToLoad*1024)^2

Fallout4.exe generally stops consistently loading games at around 300 active actors or 5Gb memory allocated. Some games manage to load up to 6Gb but freeze ~ 50% of retries.

The number of actors is constant at around 300, the memory allocated to Fallout4.exe seems to vairy depending on complexity of scenery:

Vault111ext 31 uGridsToLoad 296 loaded actors 6.2Gb memory

DiamondCityExt 15 uGridsToLoad 299 loaded actors 5.0Gb memory

GoodneighborExt 13 uGridsToLoad 288 loaded actors 4.5Gb memory

Using a scanning script to find and remove all persistent and loaded actors then forcing CellReset PurgeCellBuffers in the console removes 1,500 loaded/persistent actors from the world, reducing allocated memory by 800Mb suggesting that each actor generates a memory load of ~ 500Kb.

Comparision of the default uGridsToLoad 5 and 15 at DiamondCityExt:

Learn more here.

[RoNin1971]

I have no idea how the engine actually handles the uGrids to actually load, but as far as I know it is centered on the current cell & then 15 is a weird amount.

 

The default 5 has a + shape. Center cell + all 4 directions. The next step would be 9, including all 4 corner cells, to get a 'square' of loaded cells.

Next would be 13, adding all 4 directions again. After that you need to add 8 more (so 21) to make it a square again. & so forth.

 

At least, if you want the loaded area to be symmetric / equal in each direction.

 

Other amounts will result in an unequal number of cells loaded in each direction. (with possibly buggy performance, but that would need extensive testing, or knowledge of how the engine copes)

Edited June 28, 2023 by RoNin1971

[SKKmods]

uGridsToLoad is simply a progression of odd numbers; 3,5,7,9,11,13,15 ... 31 all work to define the loaded radius in game units ((uGridsToLoad / 2) * 4096) around the player.

 

I have been doing this stuff for years now, here is what uGridsToLoad 25 (active radius 51,200) looks like

 

The point here is not to document the basics, rather to find the actual limits depending on loaded objects and scenery in the arera.

 

[RoNin1971]

I understand you are merely looking for the limits, but I was wondering about the actual, workable, game-play limits.

 

Afaik (which isn't all that far), the grids to load is the total number of cells loaded, including the current one. So the default 5 gets you 1 cell in each of the 4 directions.

In this case 7 would get you 2 more cells loaded, instead of 4, 8, 12 etc. to keep the 'shape' of the loaded area symmetrical. (equal number of cells in each of the 4 directions.)

                       x
          x    xxx    xxx
 x  xxx  xxx  xxxxx  xxxxx
xxx xxx xxxxx xxxxx xxxxxxx
 x  xxx  xxx  xxxxx  xxxxx
          x    xxx    xxx
                       x

 5   9   13    21     25

When using 7, 11, 15, 17, 19 or 23 I have no idea which "extra" cells the game will load, but It would not be a 'round/diamond/square' shape around the player.

 

Unless I'm wrong and the grids to load is the number of cells to load in a straight line in any direction from the player outwards. (but then even numbers should not be a problem)

In which case I've said nothing and this post doesn't exist :happy:

[niston]

What I can tell with absolute certainity about this is, uGridsToLoad=7 fixes the electrical problems one can experience on Spectacle Island.

My speculation is that the ugrids number is straight line in each direction, but centered on the player. Makes sense, because then you'd always need odd numbers.

If this is the case, ugrids=5 should have the game load 25 cells, while 7 would make that 49 cells, and so on.

[SKKmods]

The furthest (actor 3d rendered) column is the empyrical demonstration of the uGrids active radius around the player:

 

Math: ((uGridsToLoad / 2) * 4096)

 

Example: uGrids 5 outside Goodneighbor the furthest 3d loaded actor is 12,764 game units from the player which is 3 cells distant (not 2.5 because the player is not always exactly in the center of the cell they are in).

 

In Language: uGridsToLoad is the diameter of 4096 game unit cells that are loaded around the player, where uGridsToLoad 5 is 5 cells (20,480 game units) diameter or 2.5 cells (10,240 game units) radius. Baseline assumes the player is exactly in the center of the cell they are in but in actual measurments there can be a +/- 2048 unit offset from that cell center.

In pictures, uGridstoLoad 5 cells (grid 3 is player center):

  1
  2
12345
  4
  5

For non native English speakers note the transitions from RADIUS (distance) to DIAMETER (cells).

 

The maximum playable anywhere in the world in my game configurations is uGridsToLoad 13 (26,000 game unit radius) to account for the volume of actors and objects downtown boston as illustrated in the clipped excel tables. More than that and Fallout4.exe will just not load a game on what looks like memory allocation limits.

 

To EZ rebut the "but no one can run more than 9 uGrids" limited beliefs here is an old GTX1060 shooting hitscan projectiles over 50,000 game units which is 25 uGrids or 13 cells back in 2017 and a more recent test using non hitscan projectiles at 35,000 game units which is 17 uGrids or 9 cells.

[RoNin1971]

To EZ rebut the "but no one can run more than 9 uGrids" limited beliefs here is an old GTX1060 shooting hitscan projectiles over 50,000 game units which is 25 uGrids or 13 cells back in 2017 and a more recent test using non hitscan projectiles at 35,000 game units which is 17 uGrids or 9 cells.

13 works fine for me (RTX2070Super) even with 4K textures, and increased distances for grass & trees.

 

It lets me look at my Red Rocket settlement and see everything I build there while standing on top of a tower within Sanctuary.

 

Haven't been to downtown Boston in a while, so not sure if it will hold up there as well.

[South8028]

 

 

To EZ rebut the "but no one can run more than 9 uGrids" limited beliefs here is an old GTX1060 shooting hitscan projectiles over 50,000 game units which is 25 uGrids or 13 cells back in 2017 and a more recent test using non hitscan projectiles at 35,000 game units which is 17 uGrids or 9 cells.

13 works fine for me (RTX2070Super) even with 4K textures, and increased distances for grass & trees.

 

It lets me look at my Red Rocket settlement and see everything I build there while standing on top of a tower within Sanctuary.

 

Haven't been to downtown Boston in a while, so not sure if it will hold up there as well.

The 1080ti takes a very long time to load 11 cells. I can't live without ReShade. With high settings and ReShade, I can't play well with more than 7 cells. Even 9 are periodic friezes. It's uncomfortable to play.

[Qrsr]

You can easily see how the engine load uGrid X by zooming in the Creation Kit. Press "T", zoom out, move mouse see how cell load ... simple