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Tex1 - TexSet

Applies to: GT3, GT4 · Extension: .img / none · Endian: Little

The Tex1 is a texture format that can hold multiple formats. It is essentially a wrapper around the PS2 Tex registers.

The header may be present in all sorts of files like models.

Size: 0x30

Field Offset Type Description
Tex1 0x00 Int Magic, (Enforced only in debug?)
Relocation Pointer 0x04 Int Relocation Pointer
Unknown Pointer 0x08 Int Normally 0?
File Size 0x0C Int File Size
Base TBP Offset 0x10 short Remapped at runtime. TBP register base
Total Blocks 0x12 short Total blocks taken by all textures in this texture set
PGLUTexture Count 0x14 short Number of textures (or mipmaps) in this texture set
GS Transfer Count 0x16 short Number of GS transfers to be made
PGLUTextures Pointer 0x18 PGLUTexture* Pointer to PGLUTexture infos
GS Transfers Pointer 0x1C GSTransfer* Pointer to GS Transfers
Unknown Pointer 0x20 void* N/A
Clut Animation Pointer 0x24 void* Unknown. Remapped by pgluMapClutAnimation
Unknown Pointer 0x28 void* N/A


Represents a texture in the texture set.

Size: 0x28

Direct GS Registers go here:

GS Transfers

Defines the transfers to be made to GS.

Transfers may be swizzled from PSMT4/8 into PSMCT32 for faster upload speed.

Size: 0x0C

Field Offset Type Description
Image Data Pointer 0x00 void* Pointer to the image data.
TBP 0x04 short Block target of the transfer's image data.
Buffer Width 0x06 byte Buffer width of the transfer.
PSM 0x07 byte Pixel surface format.
Width 0x08 byte Width of the transfer.
Height 0x0A byte Height of the transfer.

Technical documentation

Taken from PDTools


So. Tex1 might seem like a simple format, but it can get complicated really quick. If you wanna follow along, grab 010 Editor and this template

PGLUTextures defines the textures in the set, and passes GS registers for each one. Any tbp field (including mipmap) is remapped at runtime.

The GS Transfers are the hard part.

But before explaining the transfers, it's important to be familiar with the GS's block/page system, so refer to Page 161<->175 of the GS's Users Manual (Docs&Training\HardwareManuals in PS2 SDK).

The important registers to keep in mind are TBP and CBP (in tex0). These are block pointers/offsets.

Blocks kinda work as a separate coordinate system. For texture sets, some optimization is made as to where the textures go. When you have a texture that's for instance 350x350, the height and width are raised to the next power of 2, so 512x512. That leaves a space with what's rendered and what isn't, so extra data can be put there, it can be the image's palette, or another texture So don't be surprised if you see the CBP register of a texture in the middle of what would appear to be the main texture's.

Now, for GS transfers.

Suppose you have one basic texture with a palette, PDI's builder simply builds two transfers - one with the image data, the other with the palette. Simple enough, right? The problem is when larger textures or more than one texture exists within the set.

They're swizzled into buffers converted from i.e 4bit/8bit to PSMCT32 (32 bit) so the GS can load them faster. To read them (and convert to png), I used GSTextureConvert.

For more documentation:

  • Docs&Training\Starting Guides\Graphics Synthesizer Starting Guide.pdf (PS2 SDK)
  • Source in Shell\Tools\shellTexture\
  • ee\sample\graphics\textrans\bitconv

For an example, look at advertise/us/premium.img (GT4 Online). There's 3 transfers, 64x1216, 32x16 and 8x8.

So summarize, tex1 allows for 4 rather complex optimizations:

  • Textures, or palettes, can be inside the non-rendered area of other textures, to save on blocks
  • Multiple texture buffers of different formats swizzled into PSMCT32 for faster upload to GS
  • Texture data is sometimes reused when a different palette is used, to save on size
  • When a different palette is used for certain textures, the CSA register is set, which presumably avoids using an extra block for a palette.