94 lines
6.7 KiB
Markdown
94 lines
6.7 KiB
Markdown
# SPLASHPACK Binary File Format Specification
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All numeric values are stored in little‐endian format. All offsets are counted from the beginning of the file.
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---
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## 1. File Header (12 bytes)
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| Offset | Size | Type | Description |
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| ------ | ---- | ------ | ----------------------------------- |
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| 0x00 | 2 | char | `'SP'` – File magic |
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| 0x02 | 2 | uint16 | Version number (currently **1**) |
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| 0x04 | 2 | uint16 | Number of Exporter descriptors |
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| 0x06 | 2 | uint16 | Number of Texture Atlas descriptors |
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| 0x08 | 2 | uint16 | Number of CLUT descriptors |
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| 0x0A | 2 | uint16 | Reserved (always 0) |
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---
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## 2. Metadata Section
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The metadata section comprises three groups of descriptors.
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### 2.1 Exporter Descriptors (56 bytes each)
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Each exporter descriptor stores the transform and mesh metadata for one GameObject.
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| Offset (per entry) | Size | Type | Description |
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| ------------------ | ---- | ------ | --------------------------------- |
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| 0x00 | 4 | int | X coordinate (Fixed-point) |
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| 0x04 | 4 | int | Y coordinate (Fixed-point) |
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| 0x08 | 4 | int | Z coordinate (Fixed-point) |
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| 0x0C | 36 | int[9] | 3×3 Rotation matrix (Fixed-point) |
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| 0x30 | 4 | int | **Mesh Data Offset Placeholder** |
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| 0x34 | 4 | int | Triangle count in the mesh |
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### 2.2 Texture Atlas Descriptors (12 bytes each)
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Each texture atlas descriptor holds atlas layout data and a placeholder for the atlas raw data offset.
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| Offset (per entry) | Size | Type | Description |
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| ------------------ | ---- | ------ | -------------------------------------------------------- |
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| 0x00 | 4 | int | **Atlas Data Offset Placeholder** |
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| 0x04 | 2 | uint16 | Atlas width |
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| 0x06 | 2 | uint16 | Atlas height (currently always 256, for future-proofing) |
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| 0x08 | 2 | uint16 | Atlas position X – relative to VRAM origin |
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| 0x0A | 2 | uint16 | Atlas position Y – relative to VRAM origin |
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### 2.3 CLUT Descriptors (520 bytes each)
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CLUTs are the only data which is stored in the Metadata section.
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For each CLUT (Color Lookup Table) associated with an atlas texture that has a palette:
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| Offset (per entry) | Size | Type | Description |
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| ------------------ | ---- | ----------- | --------------------------------------------------------------------------------- |
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| 0x00 | 512 | uint16[256] | Color palette entries (each entry is 2 bytes 16bpp). If unused, entries are zero. |
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| 0x200 | 2 | uint16 | CLUT packing X coordinate - already in 16 pixel steps |
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| 0x202 | 2 | uint16 | CLUT packing Y coordinate |
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| 0x204 | 2 | uint16 | Palette count (number of valid palette entries) |
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| 0x206 | 2 | uint16 | Reserved (always 0) |
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---
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## 3. Data Section
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The data section contains the actual mesh and atlas raw data.
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### 3.1 Mesh Data Blocks
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For each exporter, a mesh data block is written at the offset specified in its descriptor. Each mesh block contains data for all triangles of the associated mesh.
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#### **Triangle Data Layout (per triangle – 52 bytes total):**
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| Field | Size | Description |
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| ----------------------------- | -------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| **Vertex Coordinates** | 3 vertices × 3 × 2 bytes = 18 bytes | For each vertex (v0, v1, v2): X, Y, Z coordinates (int16) |
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| **Vertex Normal** | 3 × 2 bytes = 6 bytes | Normal vector for vertex v0 (int16: nx, ny, nz) |
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| **Vertex Colors** | 3 vertices × (3 bytes color + 1 byte padding) = 12 bytes | For each vertex (v0, v1, v2): Red, Green, Blue (uint8) plus 1 byte padding |
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| **Texture Coordinates (UVs)** | 3 vertices × 2 bytes = 6 bytes | For each vertex (v0, v1, v2): U and V coordinates (uint8), adjusted by texture packing factors |
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| **UV Padding** | 2 bytes | Padding (uint16, set to zero) |
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| **Texture Attributes** | 2 + 2 + 2 + 2 = 8 bytes | Contains: <br> • Texture page attributes (uint16 – encoded from page X/Y, bit depth, dithering)<br> • Texture CLUT packing X (uint16)<br> • Texture CLUT packing Y (uint16)<br> • Reserved (uint16, set to zero) |
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*Triangles are written sequentially. Prior to writing each mesh data block, the file pointer is aligned to a 4-byte boundary.*
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### 3.2 Atlas Data Blocks
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For each atlas, a raw texture data block is written at the offset specified in its descriptor. Before writing, the file pointer is aligned to a 4-byte boundary.
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- **Raw Texture Data:**
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The atlas data is written pixel by pixel as returned by the pixel packing function. The total size equals
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*(Atlas Width × Atlas Height)* The data is prepared for a DMA transfer to the VRAM.
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---
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