Question Built-in Mipmap Streaming does stream from memory and not the storage?

I implemented custom solution for Texture Streaming so this question is just out of curiosity.

If my understanding is correct, Unity uses common asset system for any assets like Scene assets, Resources and AssetBundles.
They are loaded onto memory first, and Unity uses some contents from there.

Which means, Unity streams textures out of bundled asset on memory?
And If it does, when you say memory-budget in mipmap streaming related topic, it actually means VRAM? (When GPU with VRAM used I mean)
I could not find the information in your document.

Thank you.

 

@lyndon_unity
Thank you for the detail! I mean, really!!
I feel like I did not need to implement streaming by myself. It was only for precise memory management and possibly faster loading time.

But It begs the question, when you guys do "only loads the mapping table." part?
I assume in AssetBundle.LoadFromFile(Async)?
I mean, we have other options for creating AssetBundle like AssetBundle.LoadFromMemory(Async). But seems like it is not possible to used with streaming from disk because all the bytes have to be on memory beforehand.

If AssetBundle.LoadFromFile do many good things comprared to other methods, it is interesting and detail should be in document I think

But anyway, I really thank you! I am really glad to be able to get to grips with Unity detail here.

 

Oh dear, sorry I found the information.
https://learn.unity.com/tutorial/assets-resources-and-assetbundles#
This document has an answer. Basically LoadFromFile do "better" thing as I questioned in a previous comment.
I'm sorry for bothering you too much! Thanks!

 

Sorry I'm reviving this thread.
Direct loading from disk to GPU does work with LZ4 compression?

 

I still don't understand, does the streaming save RAM or only VRAM? On Desktop.

 

If direct loading from GPU to CPU works, then RAM is also saved. But whether it is available or not is very unclear.

Mainly purpose of Streaming in Unity seems VRAM saving.
If direct loading does not work, I do not know Unity's implementation detail, but transient ram pressure is inevitably happens. So how DRAM is saved is depending on how Unity handles this.

I want Unity to clarify what happens there more precisely in their document.

 

My understanding is that there is no (or very little) RAM cost for textures unless you make the texture readable on the CPU. There is a checkbox for that in the import settings.

Even without streaming, there is no RAM cost. There is only a temporary copy in RAM on systems that don't support uploading directly to VRAM as the texture is being loaded (it's called a staging buffer).

 

Should be available on consoles because of unified memory but not on PC. However, things are changing with direct storage, resizable bar and M1 based macs. Also not sure about smartphones. So yeah, agree, could be better documented.

 

I did not think "optimal path" is something just coming from sharing memory. But maybe is.
I just thought lyndon_unity talked about possibility of DMA.
If DMA never happens, it is very misleading. I mean, on unified memory platform, it always has to be "optimal"...

 

I just tested a large scene in the editor and my RAM usage drops and raises by 5GB as I click the checkbox. So safe to say it does work well on desktop.

I only wish shading debug mode in scene view would actually work and not just make everything invisible.
UPD: HDRP uses separate tool for debug - Window/Analytics/Rendering Debugger -> Rendering->Mip maps