Hacker News Reader

> video game assets are often enormous in size because developers refuse to implement even very basic compression because of the supposed performance impact

This claim needs some real world evidence to back it up (and usually it's not about a performance impact, but instead a perceived image quality impact).

IME a lot of care is taken for compressing asset data, and if there would be a chance to reduce the asset size by another few percent without losing too much detail (that's the important part), it would be done. In the end, textures need to end up in memory as one of the GPU compatible hardware compressed texture formats (e.g. BCx) - which is important not only for reducing memory usage, but mainly for increasing texture sampling performance on the GPU (reduced memory bandwidth and better cache locality when reading texture data from GPU memory).

Those hardware-compressed texture formats rule out any of the popular image formats like JPEG, PNG etc... that might have a better overall compression, but are hard to decode on the fly to one of the hardware texture formats (but there are now alternatives like https://github.com/BinomialLLC/basis_universal), but even a generic lossless compressor (even good old zip) on top of BCx is already a good start.

> This claim needs some real world evidence to back it up (and usually it's not about a performance impact, but instead a perceived image quality impact).

We're talking lossless compression here, so image quality is not the issue.

Fortunately someone else has already done this research. There's a tool for Windows to control the compact.exe behavior for individual folders called CompactGUI: https://github.com/IridiumIO/CompactGUI

They maintain a database of compression results here: https://docs.google.com/spreadsheets/d/14CVXd6PTIYE9XlNpRsxJ...

Reductions in storage use of greater than 50% are so common that they're hardly even worth remarking on. My experience with compressing a bunch of games is that the biggest gains come from compressing bloated asset packs. Hard to know what else could be taking up more than 50% of the storage space in a particular game.

Very interesting list, thank you! From glancing over it, poor compression mostly seems to be an 'indie phenomenon' though (which is a bit surprising, because I would expect that Unity automatically takes care of asset compression, but maybe not).

It may have tools that let you, but an indie project has 500 other fires to put out, and filesize is rarely a bottleneck.

> But for some programs (e.g. large video games), preloading all your assets is very common and decoding speed can be crucial.

Those games typically don't need lossless image compression. There are much better (and faster) algorithms for lossy texture compression, many of which can even be decoded directly by the GPU. The S3TC family is one popular example.

One interesting commercial product in this space is Oodle Texture: http://www.radgametools.com/oodletexture.htm

It's true that lossless is often not the best approach, although it's worth pointing out that anyone can implement Quite OK while both the approaches you mention are not really friendly to open source.

S3TC is patent-free as of October 2017, and is implemented in open-source graphics drivers.

Are the best available compressors for the format open source as well? That would be news to me, although I admit I haven't looked into the format in quite some time.

More generally, my point about video games was just that you can frequently cut their size by 50-75% just by turning on file compression on the game directory. Developers are obviously missing some easy wins in this area - including huge wins with lossless compression alone.

Use Universal Basis

basisu (Binomial's Basis Universal GPU Texture Codec) is pretty much state of the art here. Open source, offers excellent compression and very quickly decodes to pretty much all GPU native formats.

basisu is really impressive, but it’s not perfect for all use cases.

I tried using it in a WebGL game, but found that a) decoding was too slow, and b) the quality was too low.

PNG is much bigger, so you’d think it wouldn’t be good for a web game, but once an image has been downloaded and cached, the most important factor is the decode-and-upload time. On the web, PNG and JPEG handily beat basisu there.

In a different situation, basisu could have worked out for me. On native rather than web, maybe the decode time would have been fine. With more photographic rather than geometric assets, maybe the quality would have been fine.

PNG/JPEG are not natively understood by GPUs, though. GPUs have compressed formats they natively understand, and basisu can transcode to them quickly. You'll be burning a lot more GPU texture memory as you'll be asking the GPU store raw image data instead of compressed image data.

The advantage of using a native hardware compression format is that you save on GPU RAM, which is especially useful for web which may display on mobile systems.

That’s true, but it’s a trade-off rather than a straight win. Hardware formats do have a few disadvantages:

1. Larger size on disk

2. Reduced quality at all MIP levels

3. Complexity of each platform wanting its own special format.

Basis fixes 1 (by adding an extra layer of compression) and 3 (by transcoding to almost any format at load time). But it doesn’t fix 2, and it adds another downside -- decompressing and transcoding is relatively slow.

Look at Rich Geldreich's bc7enc_rdo.

Lossy causes some issues with normal maps, so QOI seems good for those cases where lossless is preferred to balance loading (and streamed loading) performance and space use, but yes, in general S3TC is good for sRGB color textures in PC games.

Using a lossy hardware compression (like S3TC) that's natively supported by the hardware is especially a good way to save on GPU RAM! Double the texture resolution for free, essentially.

> I'm not sure if this is common or not.

> Side note: video game assets are often enormous in size because developers refuse to implement even very basic compression

Be generous; you even said in your previous sentence you don't know if it's common or not, so how do you know developers refuse to implement basic compression? If it's that easy, I'm sure there are plenty of AAA game studios (including mine) that will hire you to just implement basic compression.

There are enormous tradeoffs to make that are platform dependent; read speeds from external media are _incredibly_ slow but from internal media may be fast. Some assets are stored on disk to mask loading/decompression. Lastly, assets are just enormous these days. A single 4k texture is just shy of 70MB before compression and a modern game is going to be made of a large number of these (likely hundreds of them), and many games are shipping with HDR - these are multiples of the size. That's becore you get to audio, animation, 3d models, or anything else.

My current projects source assets are roughly 300Gb, and our on disk size is 3GB or so. My last project was 5Tb of source assets and 60GB on disk. Of course we're using compression.

I was trying to explain to my son the other day when he was complaining about the Xbox without the drive slot. I asked him how big of a download Fortnite or call of duty were - I think he said 60 gigs and then I told him blu ray tops out at 50gb.

He understands why the Xbox doesn’t have the cd slot anymore.

Complex games used to be delivered on multiple floppy disks, later multiple CDs. I don't see the capacity of a single Blu-ray disc being a limiting factor.

I don't recall having to swap discs on PS1/2/3/4 at all.

FFVII shipped on 3 discs. Most of it was cutscenes and you better believe they were compressed to hell.

Offhand, many final fantasy games shipped on multiple discs, as did armoured core. Gran turismo and oddworld.

The last of us part 2 and GTA 5 both needed multiple discs on PS4.

PS1 had dozens of games that shipped on multiple discs, PS2 had somewhat fewer but the ones that I remember off the top of my head are Xenosaga 2 and 3.

In addition to other examples given, Metal Gear Solid 1 memorably has a disc-swap.

Games heavy on prerendered video frequently were multi-disc: Final Fantasy 7 is three discs, 8 is four, 9 is four... Xenogears is multiple discs, as is Chrono Cross. Lots of JRPGs, though not exclusively: Riven was on 5 (!) discs, again a case of a lot of prerendered content.

It was pretty rare on PS2 with DVDs, and as far as I know totally eliminated on PS3 with Blu-ray (Metal Gear Solid 4 has/had an "install swap" where it would copy over from the disc only a chapter at a time, but all coming from one disc).

Then the concept made a comeback by the tail end of the PS4's life, with several games having "play" and "install" discs, though these aren't quite the same experience, as you just use the install/data disc once then put it away. Fittingly one of these PS4 multi-disc games is the remake of Final Fantasy 7 (one that covers only a relatively small portion of the original, to boot).

It doesn't work as well for games like fortnite. Matchmaking map playlists tied to specific discs? Sure, it could be done.

One of the big limiting factors for a game like Fortnite is that the assets change significantly over time. Textures, materials, animations, audio have all changed dramatically over the last few years. There's likely very little from the initial install that is still usable, and thats before you get to file load order and fragmentation.

> Be generous; you even said in your previous sentence you don't know if it's common or not, so how do you know developers refuse to implement basic compression? If it's that easy, I'm sure there are plenty of AAA game studios (including mine) that will hire you to just implement basic compression.

The thing I said I didn't know whether it was common was keeping assets in compressed form in memory. I admit I don't know much of the specifics of how game rendering works. What I do know something about is the extremely poor compression applied to many video games in their on-disk form. I'm willing to grant that your studio may indeed be an exception to this, but the general principle isn't possible to deny. Just by enabling lossless Windows file compression on a game folder, you can frequently see the size of a game on disk drop by 50% or more, as I discuss in my comment here: https://news.ycombinator.com/item?id=34042164

Surely a lossless format designed specifically for encoding assets would be even more effective and fast than generic Windows file compression!

What performance penalty? Decoding is often faster than moving more bits from storage.