DDS.... more than just texture files

[ossie]

There's been a lot of discussion over the years about .dds as texture files, what programs they work with etc but a couple of recent conversations I've had with friends here suggest that not everyone has fully realised the "end user" benefits that can be achieved with .dds files whether you create textures or not. The .dds format creates a much smaller file size than the .ace files that were originally used for MSTS/ORTS models. If you look at the screenshot below you can see the difference in size between the .ace and .dds files in my centerflow hopper set.

Screenshot (775).png

As you can see, the .dds files are a quarter of the size of the .ace files. I don't know enough about how PCs and ORTS work to say categorically that you can run 4 .dds files with the same amount of "effort" as you can run 1 .ace file but I have done plenty of experimenting with big trains on highly populated routes and where I might get a dip in framerates running a consist made up entirely of .ace files, replacing them with .dds textures makes a huge difference in performance.

Outside of buying or downloading sets that are already using .dds files, how can you benefit? The answer is very easily. First step is to download a program called DXTBmp. It can be found here:

https://dxtbmp.software.informer.com/4.0/

Once you've downloaded the program, install it and open it:


Screenshot (776).png


Then it is a simple matter of "dropping and dragging". Open any folder in your trainset with .ace files and drag one across into the DXTBmp program and drop it. You should then be able to see some of the texture file in the DTXBmp window (1). Then click on File (2), Save as and select DDS Texture (3), select DDS DXT3 (4) and then just click on Save (5). Getting some more "bang for your buck" with texture files is as easy as that.

Screenshot (783).png Screenshot (784).png Screenshot (785).png Screenshot (786).png
Screenshot (787).png


Note: Depending on the size of the .ace files, whether they are using an alpha channel etc, there are other "save as" options that can be used besides DDS DXT3, but for a general "how to" and performance boost, DDS DXT3 is a good option. In my experience with locos and rolling stock, pretty much all .ace files can be reduced in size when converting to .dds but depending on how much dropping & dragging you want to do, I generally only worry about files over 500 KB in size.

EDIT: In relation to Eric's point, plenty of older ace files have been compressed already. If you're unsure about file sizes, when you drop and drag one into the DXTBmp window, where the file name is displayed at the very top of the program (Compressed) will appear beside the file name. If it hasn't been previously compressed dds will provide a smaller file size.

[eric]

Interesting comparison. Do you know if those ACE files were compressed? That seems a bit on the large side.

[ossie]

No Eric, they're ones I'm working on. 2048 by 2048.

[Timbit]

Thank you, Pete, for taking the time to explain this. It will be a help for me.

[yellowdog]

This could be useful, thanks! I also want to add a reminder that ORTS will look for .dds files when .ace files aren't present---so you don't have to go into all your .s files and point them to the converted texture file if you decide to convert them as described above.

[eric]

No Eric, they're ones I'm working on. 2048 by 2048.

I'd be curious to see the compressed ACE vs. DDS when you're done. I suspect they're closer in size.

My understanding is that DDS is already essentially compressed somewhat, although you can apply DXT1-5 on them depending on if there's an alpha or not.

[ossie]

You're welcome Tim & Yellowdog.

I'm not sure if I'm misunderstanding you Eric, but the 2048 x 2048 ace files I work on are the size shown in the folder. They're not compressed at that size. Once I'm finished with them I convert them to .dds and the resulting file sizes are what is shown. That way I can benefit from the better 2048 texture quality without running the large ace sizes. Left is .ace, right is .dds. To my eyes they look the same whereas 1024 textures, dxt1 etc don't look nearly as sharp but .dds3 gives me the same quality for quarter of the file size.

EDIT: Re-reading this I'm ASSUMING you were meaning ace files that had already been compressed Eric and if so, I think the short answer is they're probably about the same? I've edited the original post to take that into account. Dropping and dragging an already compressed file will show (Compressed) beside the file name. In terms of the 1024 files, a compressed one is usually around 1300 KB and uncompressed around 4200 KB. The drop & drag, .dds3 method will get that reduction from 4200 KB back to 1300 KB.

Open Rails 2025-05-15 12-22-39.png

[eric]

No, I'm not talking about zip compression, I'm referring to using AceIt with the -DXT option.

[ossie]

I guess it depends on what people are using Eric. I've never been keen on the AceIt program. I still use TGATool2 - Photoshop for my texture work then convert to .dds when I'm finished with the texture. Regardless of how the textures have been created once I started looking there were a lot of non-compressed ace files in my trainsets that I found .dds really helpful for. Drop and drag is a pretty easy way of getting a result so I thought I'd pass it on FWIW.

[emd645e3c]

You'll generally get better performance from dds if you're running a modern Nvidia GPU, as the texture work is shifted from the CPU to the GPU.

Re quality. From my experience, ace is the better quality format. I've found weathered blacks are usually the first thing that will start to go pear shaped with dds.

As for the file sizes, dds files tend to stay the same size for a given texture size. If you have a 2048 x 2048 that's fully utilised, then yes, a dds file will usually be smaller in size than an ace of it, but if it was an older file and say only 50% was used, then the ace will usually win there. A dds will stay the same regardless of area actually mapped, where as ace files grow in size with actual texture coverage.

Having said all that....I still dds everything when possible,

Steve

[scottb613]

Hi Folks,

Great iinfo.

Compression makes a big difference in file size.

Using DDS -u888 (24 Bit Uncompressed) Texture Sheets

4096 is 65,537 kb (65mb)
2048 is 16,385 kb (16mb)
1024 is  1,025 kb (1mb)

Inclusion of MipMaps will change the file size as well.

There is no difference in the base texture quality between DXT1, DXT3, and DXT5 - - - the only thing that changes is the quality of the Alpha Channel.

Regards,
Scott

[rfranzosa]

Is there another reason to switch to dds other than file size and performance with long consists? We have customers that are continuing to use MSTS, so I will include ace files for the foreseeable future. Doing both ace and dds will increase total file size, and the era I model does not include 200 car freight trains.

Thanks!


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[scottb613]

Is there another reason to switch to dds other than file size and performance with long consists? We have customers that are continuing to use MSTS, so I will include ace files for the foreseeable future. Doing both ace and dds will increase total file size, and the era I model does not include 200 car freight trains.

Thanks!


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Hi Rick,

DDS was an industry standard - so it opens the doors to using many more tools than ACE.

For people who can script/code - you can automate many of the texture processing tasks with programs like ImageMagick that includes "C" libraries.

Image Magick
https://imagemagick.org/

Regards,
Scott

[Erick_Cantu]

ACE and DDS are just container formats. There are no intrinsic size or performance differences between them. What determines the size and performance impact are the options they are exported with. A 32-bit 2048 x 2048 pixel image with mipmaps will be the same size and have the same effect on performance whether it's exported in BMP, DDS, or ACE format because BMP, DDS, and ACE are just the containers for the actual 32-bit extended bitmap data inside. Likewise, a DXT3 2048 x 2048 pixel image without mipmaps will also be the same size regardless of the container since the actual format of the data is DXT3.

Using DDS allows the developer several important freedoms:

1. Future-proofing. DDS is a universal format. ACE is not.
2. Freedom from AceIt and TgaTool. You need a license to do payware with either of these. You can't actually export high resolution images with MakeAce, necessitating the aforementioned tools to do any serious hi-res work. You can export DDS in any size or format you want from your paint program of choice without restriction with NVIDIA's plugins.
3. TgaTool/AceIt can't export DXT5, which handles gradient alpha far better than DXT3 ever did. It's not 2005 anymore and there's no reason to ever use a 1-bit alpha texture with its silly, hard, blocky, aliased edges in 2025.

[rfranzosa]

Thanks, Erick


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