The example here is my photograph "mysoup" which I make CC0. While most game textures are not like photographs, this is typical of the results we see. To try Oodle Texture on your own images contact RAD Game Tools for an evaluation. You can also see more sample encodings on real game textures at the Oodle Texture web site.
I will be showing "mysoup" encoded to BC7 here, which is the format commonly used by games for high quality textures. It is 8 bits per texel (vs 24 for source RGB). The BC7 images I provide here are in DDS format; they are not viewable by normal image viewers, this is intended for game developers and technical artists to see real game data.
I have made these BC7 DDS with Oodle Texture in "BC7 RGBA" mode, which attempts to preserve the opaque alpha channel in the encoding. I would prefer to use our "BC7 RGB" which ignores alpha; this would get slightly higher RGB quality but can output undefined in alpha. Because many third party viewers don't handle this mode, I've not used it here.
I will also show the encoding of a few different maps from a physically based texture : coral_mud_01 from texturehaven.com (CC0), to show a sample of a full texture with diffuse, normal, and attribute maps.
I show RMSE here for reference, you should be able to reproduce the same numbers on the sample data. The RMSE I show is per texel (not per channel), and I compute only RGB RMSE (no A). Note that while I show RMSE, Oodle Texture has been run for Perceptual quality, and visual quality is what we hope to maximize (which sacrifices RMSE performance).
Oodle Texture is not a compressor itself, it works with the back end lossless compressor of your choice. Here I will show sizes with software Kraken at level 8 and zlib at level 9. You can download the data and try different back end compressors yourself. Oodle Texture works with lots of different lossless back end compressors to greatly increase their compression ratio.
The "mysoup" images are 1024x1024 but I'm showing them shrunk to 512x512 for the web site; you should always inspect images for visual quality without minification; click any image for the full size.
Download all the files for mysoup1024 here : (BC7 in DDS) :
mysoup1024_all.7z
Download all the files for coral_mud_01 here : (BC7,BC4,BC5 in DDS) :
coral_mud_01.7z
mysoup1024.png :
original uncompressed RGB :
click image for full resolution.
baseline BC7 :
(no RDO, max quality BC7)
RMSE per texel: 2.7190
Kraken : 1,048,724 -> 990,347 = 7.555 bpb = 1.059 to 1
Kraken+bc7prep : 1,080,696 -> 861,173 = 6.375 bpb = 1.255 to 1
zlib9 : 1,048,724 -> 1,021,869 = 7.795 bpb = 1.026 to 1
BC7 data is difficult for traditional compressors to handle. We can see here that neither Kraken nor zlib can get much compression on the baseline BC7, sending the data near the uncompressed 8 bits per texel size of BC7.
Oodle Texture provides "bc7prep", which is a lossless transform that makes the BC7 data more compressible. "bc7prep" can be used with Kraken, zlib, or any other back end compressor. "bc7prep" does require a runtime pass to transform the data back to BC7 that the GPU can read, but this can be done with a GPU compute shader so no CPU involvement is needed. Here bc7prep helps quite a bit in changing the data into a form that can be compressed by Kraken.
rdo lambda=5 :
RDO in near lossless mode
RMSE per texel: 2.8473
Kraken : 1,048,724 -> 849,991 = 6.484 bpb = 1.234 to 1
Kraken+bc7prep : 1,080,468 -> 767,149 = 5.680 bpb = 1.408 to 1
zlib9 : 1,048,724 -> 895,421 = 6.831 bpb = 1.171 to 1
In near lossless mode, Oodle Texture can make encodings that are visually indistinguishable from baseline, but compress much better. At this level, Oodle Texture RDO is finding blocks that are lower rate (eg. compress better with subsequent Kraken compression), but are no worse than the baseline choice. It's simply a smarter encoding that considers rate as well as distortion when considering the many possible ways the block can be encoded in BCN.
Note that when we say "near lossless RDO" we mean nearly the same quality as the baseline encoding. The baseline encoding to BC7 forces some quality loss from the original, and this RDO setting does not increase that. The RMSE difference to baseline is very small, but the visual quality difference is even smaller.
We believe that legacy non-RDO encodings of most texture types should never be used. Oodle Texture RDO provides huge wins in size with no compromise; if you need max quality just run in near lossless mode. It simply makes a better encoding to BC7 which is much more compressible. Many common BC7 encoders produce worse quality than Oodle Texture does in near-lossless mode.
rdo lambda=40 :
RDO in medium quality mode
RMSE per texel: 4.2264
Kraken : 1,048,724 -> 509,639 = 3.888 bpb = 2.058 to 1
Kraken+bc7prep : 1,079,916 -> 455,747 = 3.376 bpb = 2.370 to 1
zlib9 : 1,048,724 -> 576,918 = 4.401 bpb = 1.818 to 1
At lambda=40 we are now trading off some quality for larger rate savings. At this level, visual differences from the original may start to appear, but are still very small, and usually acceptable. (for example the errors here are far far smaller than if you encoded to BC1, or even if you encoded with a poor BC7 encoder that reduces choices in a hacky/heuristic way).
At this level, Kraken is now able to compress the image nearly 2 to 1 , to 3.888 bits per texel, starting from baseline which got almost no compression at all. We've shrunk the Kraken compressed size nearly by half. This also means the content can load twice as fast, giving us an effective 2X multiplier on the disk speed. This is a HUGE real world impact on game content sizes with very little down side.
zlib has also benefitted from RDO, going from 1,021,869 to 576,918 bytes after compression. Kraken does a bit better because it's a bit stronger compressor than zlib. The difference is not so much because Oodle Texture is specifically tuned for Kraken (it's in fact quite generic), but because more compressible data will tend to show the difference between the back end compressors more. On the baseline BC7 data, it's nearly incompressible, so the difference between Kraken and zlib looks smaller there.
Download all the "mysoup" files here : (BC7 in DDS) :
mysoup1024_all.7z
Summary of all the compression results :
baseline BC7 :
Kraken : 1,048,724 -> 990,347 = 7.555 bpb = 1.059 to 1
Kraken+bc7prep : 1,080,696 -> 861,173 = 6.375 bpb = 1.255 to 1
zlib9 : 1,048,724 -> 1,021,869 = 7.795 bpb = 1.026 to 1
RDO lambda=5 :
Kraken : 1,048,724 -> 849,991 = 6.484 bpb = 1.234 to 1
Kraken+bc7prep : 1,080,468 -> 767,149 = 5.680 bpb = 1.408 to 1
zlib9 : 1,048,724 -> 895,421 = 6.831 bpb = 1.171 to 1
RDO lambda=40 :
Kraken : 1,048,724 -> 509,639 = 3.888 bpb = 2.058 to 1
Kraken+bc7prep : 1,079,916 -> 455,747 = 3.376 bpb = 2.370 to 1
zlib9 : 1,048,724 -> 576,918 = 4.401 bpb = 1.818 to 1
coral_mud_01 :
You can get the source art for coral_mud_01 at texturehaven.com. I used the 1k PNG option. On the web site here I am showing a 256x256 crop of the images so they can be seen without minification. Download the archive for the full res images.
coral_mud_01_diff_1k :
diffuse (albedo) color in BC7 (RGBA)
| BC7 non-RDO | BC7 lambda=30 | BC7 lambda=50 |
| RMSE 3.5537 | RMSE 4.9021 | RMSE 5.7194 |
| 7.954 bpb | 5.339 bpb | 4.683 bpb |
 |
 |
 |
coral_mud_01_Nor_1k.png:
normal XY in RG channels only in BC5
BC5 decodes to 16 bit
RMSE is RG only
| BC5 non-RDO | BC5 lambda=30 | BC5 lambda=50 |
| RMSE 3.4594 | RMSE 5.8147 | RMSE 7.3816 |
| 8.000 bpb | 5.808 bpb | 5.083 bpb |
|
|
|
coral_mud_01_bump_1k.png:
bump map, single scalar channel
BC4 decodes to 16 bit
| BC4 non-RDO | BC4 lambda=30 | BC4 lambda=50 |
| RMSE 3.2536 | RMSE 4.1185 | RMSE 5.2258 |
| 7.839 bpb | 6.871 bpb | 6.181 bpb |
|
|
|
Single scalar channels in BC4 is an unusual usage for games. Typically several scalar channels would be combined in a BC7 texture.
Compressed sizes are with software Kraken at level 8, no additional filters. "bpb" means "bits per byte", it's the compressed size in bits, per byte. The non-RDO textures in coral_mud all get almost no compression at all with Kraken. With RDO that improves to around 5 bpb, which is an 8:5 ratio or 1.6 to 1
With BC7 and BC5, the "bpb" size is also the number of bits per texel, because they start at 8 bits per texel when uncompressed. If RDO can improve BC7 to 4 bits per texel, that means it's now the same size on disk as uncompressed BC1, but at far higher visual quality. (2:1 on BC7 is a bit more than we typically expect; 8:5 or 8:6 is more common)
Download all the files for coral_mud_01 here : (BC7,BC4,BC5 in DDS) :
coral_mud_01.7z
Read more about Oodle Texture on the RAD Game Tools web site
2 comments:
We're kind of scrambling at the last minute to get some sample content together, I thought I'd say a word about why.
During development of Oodle Texture we have used multiple varied test sets. The most useful data came from some game developers and partners who kindly shared some real game data with us, and that's what we've used to drive development.
During development we've used multiple methods of analysis to verify quality. We use slow offline computational perceptual metrics, like MS-SSIM-IW (regular SSIM is terrible, don't use it), PSNR-HVS-M, etc. We examine things with eyes. We run over tests sets and don't just look at averages or totals, we look at charts that show behavior on each individual image to look at outliers.
Unfortunately for doing public announcements we can't use the real game textures we've used for development, so we're trying to find some CC0 content that we can post.
Some people have suggested the sites like cc0textures, sharetextures, etc. While these are awesome resources, and we use them, they are not exactly real game textures. Some of them have the source art in JPEG which biases the artifacts in a strange way. They tend to have all the maps in lots of grayscale images, which games don't do; games typically will pack things like specular and AO maps together into the alpha channel of the diffuse, or multiple scalar maps into one BC7. So while they are cool, they're not really representative samples of the content we expect to run on.
All that said, I'll work on putting up some more samples of various types.
I updated the post to add a sample run on "coral_mud_01"
Thanks to cc0textures.com, texturehaven.com, and all the other sites out there providing CC0 content. They're not exactly like real game content, and we don't use them for our internal test sets, but they are great for posting samples on the web sites.
Post a Comment