Texture Compression

Comparison of texture compressions

The DirectX texture format .dds supports different compression types. They can be set on export, from example when using the Nvidia Texture Tools, or they can be changed in tools such as OpenIV for GTA IV and V. Block compression formats are used most commonly, they give the best compromise between size and quality. In some cases however, older block compression formats such as DXT (BC1, BC2 and BC3) lose color information, which is especially noticeable with grey colors. Newer formats such as BC7 combine a low file size with very high quality, but may not be supported by older games.

Which compression should I use?

This table compares the most commonly used formats. File size is for a 1024x1024 texture with mipmaps. For .dds files, the complexity of a texture does not affect its size, only the resolution does.

Avoiding greyscale discoloration with DXT compression

Often when converting to DDS, choosing any of the DXT formats will cause the discoloration due to the compression of the texture and leave you with a purple or green shade hanging over your texture. This table ranging from RGB 0, 0, 0 to RGB 255, 255, 255 can be used to see exactly what colors would be altered after export to DDS.

As an example, colors such as RGB 31, 31, 31 would result in being RGB 30, 31, 30. The green being a mere one above red and blue results in this green shade. Other examples are the inverse of that, such as RGB 40, 40, 40 which results in RGB 41, 40, 41 after compression. Because the green is lower in this case, the color takes on the purple shade.

Greyscale Compression Table

Compression algorithms differ for different tools. This comparison was created for the Nvidia Texture Tools Exporter.

The colors that resulted in grayscale RGB colors without any green or purple dominance in the DDS file are marked on the table with green ticks.

Sometimes, the compressed color is slightly different, an example of this is RGB 2, 2, 2 which results in RGB 3, 3, 3. Regardless of the rounding, its still equal and can be used but the key is to use the value before compression which was originally RGB 2, 2, 2, as marked in the table.

Color Swatches for Photoshop

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Safe DXT greyscale color palette for Photoshop/Illustrator

This is an Adobe Swatch Exchange file which contains swatches for all greyscale colors which can be safely exported by the NVidia Texture Tools DDS exporter without discoloration/tinting due to DXT compression.

To install, simply open the Swatches panel in either Photoshop or Illustrator, click the menu button in the top right corner of the panel, and select "Load Swatches" or "Open Swatch Library > Other Library" and select the provided file. Use any color in the swatch group for greyscale…

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PNWParksFan

January 13, 2023 at 9:12 AM