Microsoft and Sony are both aiming for some very impressive feats with their upcoming consoles, but they’re both going about it in different ways. While Sony are going all-in on the PS5’s impressive SSD, Microsoft have emphasized the Xbox Series X’s Velocity Architecture quite a bit, even having mentioned just recently that it will “fundamentally rethink how a developer can take advantage of the hardware provided by the Xbox Series X.”
One key part of the Velocity Architecture puzzle is Sampler Feedback Streaming, something that is seemingly going to be central to the Xbox Series X’s I/O optimization. There’s a lot to it, but in plain and simple terms, Sampler Feedback Streaming allows the console to only load in textures and assets that are only needed in a game at that moment rather than having significantly more of them loaded in in the background just in case they’re needed, which means a lot of space and memory are freed up for the CPU to focus on other things. But while this all sounds impressive on paper, how impactful is it actually going to be?
Well, according to Gavin Stevens – co-founder and design lead of indie studio Team Blur Games – is surely excited about it. Taking recently to Twitter, Gavin explained what exactly Sampler Feedback Streaming is, ow developers are going to use it, how much of a difference it is going to make, and how it’s going to help the Xbox Series X level the playing field with the PS5’s SSD.
Stevens started out by explaining in some detail why exactly streaming in of assets and textures is so memory intensive. There’s a lot of nitty-gritties that he goes into, but here’s the gist- in-game assets are made up of multiple textures, and put together, these textures take up a lot of space in the memory. Compression makes textures smaller in size, but then you get to things like mips (lower resolution versions of the same asset), which only increase in quantity as the textures go higher in resolution (which, of course, they will as consoles become capable of producing better visuals). Effectively, what this means is that loading in heavy amounts of textures become unavoidable.
This, Stevens, explains, is where Sampler Feedback Streaming comes in. As Stevens explains, Sampler Feedback Streaming only loads in textures and mips that are required, while ignoring everything else, which effectively means that developers will be able to allow in high quality textures, but in smaller quantities based on requirement, and at much faster speeds.
Stevens adds that the PS5’s SSD is undoubtedly faster than the Xbox Series X’s, but states that while Sony focused entirely on their SSD, Microsoft have divvied their attention across several solution, such as Sampler Feedback Streaming, which in particular, in Stevens’ words, “levels the playing field somewhat.”
“However, there is more than one way to skin a cat, and SFS is an absolute game changer in keeping up with the (brilliant) PS5 drive,” Steven writes.
You can read Steven’s entire Twitter thread for a much more detailed breakdown below.
First, textures. Games are made up of textures, of which a single surface can contain several. What looks like one simple visual asset to you in the game world, can actually contain many. Commonly, surfaces are created with a bare minimum of: Diffuse, Specular and Normal. 2/2 pic.twitter.com/cPlHu8QWdX
— Gavin Stevens 🍕 (@GTS_Tweets) July 16, 2020
So, a standard texture set contains several assets. Assets will vary in size depending on resolution, and compression method used. For reference, a standard 2048×2048 texture set will be D/N/S, of which each file is 12mb, so, 36mb in total. 4/4
— Gavin Stevens 🍕 (@GTS_Tweets) July 16, 2020
However, that's not a fair assumption, as usually, we compress these images to save file size on disk. But we also do other tricks, such as greyscale specular, or lower resolution spec maps. There are many ways to save size here. 6/6
— Gavin Stevens 🍕 (@GTS_Tweets) July 16, 2020
…scene, if you use too low res an image it will look awful, but likewise too high res an image will look utterly terrible at distance and appear to what we call sparkle (almost like looking at a pixelated version of the image). So we blend between these textures as needed. 8/8 pic.twitter.com/TbsRfzZRPn
— Gavin Stevens 🍕 (@GTS_Tweets) July 16, 2020
…means 512×512 would be our source, and then 256×256, 128, 64, 32, 16 etc. So as you can see, the higher resolution your base asset is, the more mips are required. Again remember this is done for EVERY asset, texture wise. 10/10
— Gavin Stevens 🍕 (@GTS_Tweets) July 16, 2020
If the player is in your face, or if he's 1 mile away shooting somebody else, it doesn't matter… If the engine thinks that asset is needed, its in memory. Remember, I said its not just ONE asset either, but multiple. So, think of the sheer amount of data that could be… 12/12
— Gavin Stevens 🍕 (@GTS_Tweets) July 16, 2020
SFS will essentially only load the required mips and totally ignore everything else that would usually need to be called into memory. Why is that important?
Simple.
Because now, that half a gigs worth of uncompressed data, is just 576……kb. 14/14 pic.twitter.com/gJKnvSFfj1
— Gavin Stevens 🍕 (@GTS_Tweets) July 16, 2020
So now, you are loading in much, much, much less texture data.
Why is that such a big deal?
Because now, you need much LESS IO throughput to move assets in and out of memory. You can load things quicker, for less hit, but still at the quality desired. 16/16
— Gavin Stevens 🍕 (@GTS_Tweets) July 16, 2020
The PS5 SSD is faster than the series X. Of that, there is absolutely nobody with a brain who will tell you otherwise. However, there is more than one way to skin a cat, and SFS is an absolute game changer in keeping up with the (brilliant) PS5 drive. 18/18
— Gavin Stevens 🍕 (@GTS_Tweets) July 16, 2020
Both machines are incredible. BOTH. But while Sony put all their eggs in an SSD basket, MS divided the talent up for everything. The XSX SSD is a damn fine piece of kit with some impressive IO optimisations of its own that gets ignored, but… 20/20
— Gavin Stevens 🍕 (@GTS_Tweets) July 16, 2020
I cannot wait for the 23rd. Come on @xbox, bring the fire, bring the bombs. Lets put this "xbox has no games" meme to bed.
Regardless of if you're blue or green, we are in for a damn fine generation guys.
Lets do this. 22/22
— Gavin Stevens 🍕 (@GTS_Tweets) July 16, 2020
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