GTX\GSH (File Format)
The GTX/GSH file formats are used in various Wii U games, including MK8.
GSH stands for GX2 shader file, while GTX stands for GX2 texture file.
Header
Every GTX/GSH file begins with an 0x20 byte Gfx2 header.
| Offset | Size | Description |
|---|---|---|
| 0x00 | 4 | "Gfx2" File identifier, ASCII string. |
| 0x04 | 4 | Size of header in bytes. Must be the real size (0x20), or header (and hence file) is unreadable. |
| 0x08 | 4 | Major version number. Must be 0x07, or header is unreadable. |
| 0x0C | 4 | Minor version number. Must be 0x01. |
| 0x10 | 4 | GPU version for which this file is designed for. |
| 0x14 | 4 | Align mode. |
| 0x18 | 4 | Reserved, Always 0x00. |
| 0x1C | 4 | Reserved, Always 0x00. |
| 0x20 | End of Gfx2 header. | |
Data Blocks
After the header comes some data blocks, data blocks contain a 0x20 byte BLK{ block header followed by data specified by the block type.
Block Header
| Offset | Size | Description |
|---|---|---|
| 0x00 | 4 | "BLK{" Header of the block, ASCII string. |
| 0x04 | 4 | Size of block header in bytes. |
| 0x08 | 4 | Major version number. Must be 0x01 or header is unreadable. |
| 0x0C | 4 | Minor version number. Must be 0x00. |
| 0x10 | 4 | Block type, it determines the type of the following data. |
| 0x14 | 4 | Size of the following data. In bytes, always 0x9C if the block type is 0x0B. |
| 0x18 | 4 | A unique identifier for this block, allowing it to be referenced by other blocks |
| 0x1C | 4 | An incrementing index for each instance of a given type. |
Block types
IIRC Block type 0x04 doesn't exist, I hope so.
| Type | Description |
|---|---|
| 0x00 | Not actually a valid Block type. |
| 0x01 | Follows this block header the end of the file. |
| 0x02 | Follows this block header padding. (Used to align following data) |
| 0x03 | Follows this block header Vertex shader header. |
| 0x05 | Follows this block header Vertex shader program. |
| 0x06 | Follows this block header Pixel shader header. |
| 0x07 | Follows this block header Pixel shader program. |
| 0x08 | Follows this block header Geometry shader header. |
| 0x09 | Follows this block header Geometry shader program. |
| 0x0A | Same as 0x09? (Duplicate?) |
| 0x0B | Follows this block header the Image header. |
| 0x0C | Follows this block header the swizzled Image data. |
| 0x0D | Follows this block header the swizzled Mipmaps data. |
| 0x0E | Follows this block header Compute shader header. |
| 0x0F | Follows this block header Compute shader program. |
| 0x10 | Treated like a 0x02 block, users can do what they want with this block. |
Image info
The image info directly follows the block header that has a block type 0x0B, and should exactly have a size of 0x9C:
| Offset | Size | Description |
|---|---|---|
| 0x00 | 4 | Dimension. Indicates the "shape" of a given surface or texture (see line 849 here). |
| 0x04 | 4 | Texture Width. Width of the texture in pixels. |
| 0x08 | 4 | Texture Height. Height of the texture in pixels. |
| 0x0C | 4 | Depth. |
| 0x10 | 4 | Number of Mipmaps. |
| 0x14 | 4 | Texture Format. Go to line 589 on this page for explanation and format values. |
| 0x18 | 4 | AA Mode. Indicates the AA mode (number of samples) for the surface (see line 865 here). |
| 0x1C | 4 | Usage. Indicates how the given surface may be used (see line 823 here). |
| 0x20 | 4 | Data Length. Length of texture data in bytes. |
| 0x24 | 4 | Data Pointer? |
| 0x28 | 4 | Mipmaps Data Length. Length of mipmaps data in bytes. |
| 0x2C | 4 | Mipmaps Pointer? |
| 0x30 | 4 | Tile Mode. Indicates the desired tiling mode for the surface (see line 795 here). |
| 0x34 | 4 | Swizzle Value. |
| 0x38 | 4 | Alignment. Always 512 * bytes per pixel. |
| 0x3C | 4 | Pitch. |
| 0x40 | 0x0D | Mip Offset. Offset for each mipmap? |
| 0x4D | 0x2B | Unknown. Mipmaps related? (Almost always 0 in textures with no mipmaps) |
| 0x78 | 4 | Number of Mipmaps. Again... |
| 0x7C | 4 | Unknown. Always 0. |
| 0x80 | 4 | Unknown. Always 1. |
| 0x84 | 4 | Unknown. Always 0x00010203. (Is this some kind of a pattern? 00->01->02->03) |
| 0x88 | 0x14 | Unknown. |
Formats
TODO.
Swizzling
Reverse-engineering the swizzling was a nightmare, so documenting it will be too. The following code can swizzle/deswizzle data if you give it the right values.
Basically call swizzle() by giving it the width, height, depth, format (in hex), tileMode, swizzle value, pitch, and data.
If you're swizzling then set do_swizzle to True. If you're deswizzling then set do_swizzle to False.
Tools
The following tool can extract and generate GTX files:
- GTX Extractor, by AboodXD