What are DXT and BC texture compression?
DXT and BC are names for the same family of block compression formats that graphics cards can read directly without unpacking. Each format squeezes every 4x4 block of pixels into a fixed number of bytes, so a compressed texture uses between a quarter and an eighth of the memory of the uncompressed image. Textures in a GTA V .ytd are normally stored this way, most often as DXT1 for opaque images and DXT5 for images with transparency. An uncompressed texture in a vehicle mod is one of the quickest ways to an oversized file.
The formats compared
DXT is the older DirectX name and BC (block compression) is the newer one. DXT1, DXT3 and DXT5 are the same formats as BC1, BC2 and BC3.
| Format | Also called | Bits per pixel | Alpha | Typical use |
|---|---|---|---|---|
| DXT1 | BC1 | 4 | None, or 1-bit cut-out | Opaque colour textures |
| DXT3 | BC2 | 8 | 4-bit, stepped | Rare; sharp-edged transparency |
| DXT5 | BC3 | 8 | Smooth, interpolated | Textures with soft transparency |
| ATI1 | BC4 | 4 | Single channel only | Greyscale masks |
| ATI2 | BC5 | 8 | Two channels only | Normal maps |
| BC7 | 8 | Optional, high quality | High-quality colour, with or without alpha | |
| A8R8G8B8 | Uncompressed | 32 | Full 8-bit | Should be avoided for large textures |
The bits-per-pixel column is what decides memory use. At the same resolution DXT5 is twice the size of DXT1, and uncompressed is eight times the size of DXT1.
To fix this in an existing resource, the Texture Optimizer shrinks oversized .ytd files in your browser. Open the Texture Optimizer
What that means in megabytes
| Resolution | DXT1 / BC1 | DXT5 / BC3 / BC7 | Uncompressed 32-bit |
|---|---|---|---|
| 512 x 512 | 0.125 MiB | 0.25 MiB | 1 MiB |
| 1024 x 1024 | 0.5 MiB | 1 MiB | 4 MiB |
| 2048 x 2048 | 2 MiB | 4 MiB | 16 MiB |
| 4096 x 4096 | 8 MiB | 16 MiB | 64 MiB |
These figures are for the top level only; mipmaps add about a third. A single uncompressed 2048 px texture, or a single 4096 px DXT5 texture, is enough to push a .ytd to the 16 MiB mark at which FiveM warns about oversized assets.
Choosing a format
- No transparency: DXT1. This covers most body, interior, tyre and underbody textures.
- Soft transparency or a meaningful alpha channel: DXT5. Examples are decals, glass overlays, badges with soft edges and textures whose alpha channel stores a mask the shader uses.
- Hard cut-out transparency: DXT1 with 1-bit alpha is enough for grilles and meshes where each pixel is either solid or absent.
- Visible banding or blockiness in smooth gradients: BC7 gives noticeably better quality than DXT5 at the same size.
- Never by default: uncompressed. It is occasionally justified for tiny textures where block artefacts would show, and not otherwise.
A common waste in vehicle mods is DXT5 used for textures whose alpha channel is entirely opaque. Saving those as DXT1 halves their size with no visible change. Check before converting, though: some vehicle shaders read the alpha channel for something other than transparency.
Things to know before recompressing
- It is lossy. Each time an image is decoded and compressed again, quality drops slightly. Convert once, from the best source available.
- Blocks are 4 x 4 pixels. Dimensions should be multiples of four, and in practice powers of two, so that mip chains work.
- Compression does not change resolution. A 4096 px DXT1 texture is still 8 MiB. Format and resolution are two separate levers, and resolution is the bigger one.
- Reducing resolution by dropping a mip level needs no recompression, which is why it is the safest first step. The Texture Optimizer takes that approach.
To see the format of each texture, open the dictionary in OpenIV, or run the resource through the Resource Inspector. The .ytd optimization guide covers the manual workflow.
Frequently asked questions
What is the difference between DXT1 and DXT5?
DXT1 uses 4 bits per pixel and has no smooth alpha channel. DXT5 uses 8 bits per pixel and adds a smooth alpha channel. Use DXT1 for opaque textures and DXT5 when transparency is needed.
Are DXT and BC the same thing?
Yes for the older formats: DXT1 is BC1, DXT3 is BC2 and DXT5 is BC3. BC4, BC5 and BC7 are later additions to the same family.
Which texture format is best for FiveM cars?
DXT1 for textures without transparency and DXT5 for those with it covers nearly every case. Avoid uncompressed textures, which are four to eight times larger.
Tools for this
Related guides
Related terms
More in Streaming & Optimization: LOD (Level of Detail)
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