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godescalcus

What's VRAM and how is it used by games?

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Sorry about a rookie question. I'm still puzzled by how exactly VRAM is used by Skryim and other games. For what I know "oldrim" can only use 4Gb of video ram, but what does it do with it?

1 - What's stored in VRAM at any given moment? Stuff like assets, textures, and what else? Or is it used to store the processed output of the rendering engine? 

2 - If assets get stored in VRAM, are they kept there permanently? I mean, does the game load them at startup and keep them there for quicker usage? Or do the contents of VRAM get replaced/refreshed during the game? Does the game try to keep all assets permanently in VRAM or just the ones used in rendering (the current cell and immediate cells)?

3 - How can we criteriously lighten the load on VRAM - which assets have the most impact, and which won't make any difference if we change their resolution?

4 - What relative impact do new assets vs. asset replacers like textures and high poly meshes? Any impact on VRAM or mostly on the processing effort?

 

Why are textures sometimes glitchy in game (like low-res faces on high res skin textures, or square blood splatters) and other times (during the same game or with the same setup) they come out right?

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10 minutes ago, godescalcus said:

can only use 4Gb of video ram

You mean Skyrim LE can only use 3 Gb RAM.  If so then don't forget the 4Gb-patch that's widely used for older games such as Morrowind and Oblivion.

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1 hour ago, Leonardo said:

You mean Skyrim LE can only use 3 Gb RAM.  If so then don't forget the 4Gb-patch that's widely used for older games such as Morrowind and Oblivion.

I use it for Oblivion. Should I use it with skyrim? I've seen no mention of it so far... And I have seen mentioned that video ram is capped at 4gb in windows 8 and 10 for the 32 bit skyrim, dunno why.

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I did that too with Helgen Reborn, Falskaar, IW. Should I optimize other mods too? I still use Wyrmstooth for example. I also have Gamwich's performance bethesda hr textures and have been progresslively using those over Cabal's while trying to improve performance, but i'm not sure there's a huge gain (except that in terms of file size the former seem to be about half of the latter). But I'm keeping aMb content addon for variety... Also using a combination of noble skyrim performance with vivid landscapes performance as replacements. And Northfire mountains 2k. Should any of these be optimized?

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No idea about those- but generally speaking most of the seasoned mod authors bundle their mods with textures optimised in the box. There's a thread with more info for SSE here.

Quote

2 - If assets get stored in VRAM, are they kept there permanently? I mean, does the game load them at startup and keep them there for quicker usage? Or do the contents of VRAM get replaced/refreshed during the game? Does the game try to keep all assets permanently in VRAM or just the ones used in rendering (the current cell and immediate cells)?

It's all fairly dynamic, cells (quadrants?) and such are loaded and unloaded according to inifile settings as you move through the worldspace .

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1: Textures, basically textures

2: It's dynamic and is being replaced on the fly. There's a speed limit though usually coming into effect when what you can see on screen no longer fits into the VRAM completely and needs to be replaced during the calculation of each frame. There are programs around to tell you how much your VRAM is occupied at any given time. You will start to see stutters if you get into regions close to 90%.

3: Texture resolution obviously has the most impact. But also Stuff like level of detail/range of sight at which objects in the distance are loaded. Textures have several layers of detail, with receding VRAM impact. Those load the further away an object is, thus lowering VRAM usage for far away objects. There are options to specifically tell the game to load higher or lower level of details of a texture

4: There's no difference really, if they use the same texture resolution and compression level (textures are also compressed with a lossy format most of the time, some mods prefer not to do that, but that's nothing you would need to worry about. Most authors make the right decision).

 

Now as for why textures may sometimes come out right or wrong is a lot more complicated and also depends on the way they are applied. Blood decals for example are put over a surface by the engine to cover what is beneath it. This only works on specified surfaces though, some are missing due to error or excluded due to some even more obscure reasons. Now if a blood decal (texture) is applied to an area where it crosses from a place it is allowed to be displayed to a place it isn't, it simply cuts off leaving an odd shape.

The texture itself will still be displayed in the area it is allowed to, resulting in very nice looking non blurry blood (this is what a high resolution texture, using all that precious VRAM, does) splatter, but in the part where it isn't allowed by the engine, it simply is missing. Nothing you could do there, at least nothing do to texture and VRAM allocation.

 

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