NCER (NITRO-System Cell for Runtime) files store OBJ cell data for the 2D engine. It follows the NNS G2D Binary File Format. NCER files use file signature 'NCER'.
CEBK Block#
The CEBK (Cell Bank) block defines the set of cells in this file. The structure is as follows:
| Offset | Type | Meaning |
|---|---|---|
| 0x00 | u16 | Number of cells |
| 0x02 | u16 | Bank attributes. If the cell bank stores bounding rectangle info for each cell, this will be 1. Otherwise, this will be 0. |
| 0x04 | void * | Pointer to cell data. This is relative to the start of this structure and fixed up at load time. |
| 0x08 | u32 | Mapping mode. This can be 1D 32K (0), 1D 64K (1), 1D 128K (2), or 1D 256K (3), or 2D (4). |
| 0x0C | void * | VRAM transfer data pointer relative to the start of this structure. and fixed up at load time. If VRAM transfer characters are not used, this will be NULL. |
| 0x10 | void * | Pointer to string bank (fixed up at load time). This can be NULL. |
| 0x14 | void * | Pointer to user extended cell attribute data (fixed up at load time). This can be NULL. |
The cell data in the cell bank is structured as:
| Offset | Type | Meaning |
|---|---|---|
| 0x00 | u16 | Number of OAM attributes in this cell. |
| 0x02 | u16 | Cell attributes. |
| 0x04 | void * | Pointer to OAM attribute data relative to the start of the OAM data. The OAM data starts immediately after the cell array. |
| 0x08 | s16 | *Max X |
| 0x0A | s16 | *Max Y |
| 0x0C | s16 | *Min X |
| 0x0E | s16 | *Min Y |
Here * denotes fields only present when bounding rectangle is specified in the CEBK structure. This alters the size of the cell data, and needs to be taken into account when calculating the offset to OAM data.
The cell attributes is a bit field. The lowest 6 bits of these attributes represent the size of the circle of minimal radius centered at the center of this cell's bounding box that contains every OBJ (or opaque pixel) in the cell. This is divided by 4 and rounded up, with a maximum value representing a radius of 252 pixels. Bit 8 indicates if the cell uses H flip, bit 9 indicates if the cell uses V flip, bit 10 indicates if the cell uses both H and V flip, and bit 11 indicates if the cell has bounding box information.
Some cell files use VRAM transfer characters for animation. This involves transferring graphics to VRAM on the fly. This allows all graphics not to be loaded into VRAM at a time. For these kinds of animation, the VRAM transfer data pointer will be non-NULL. The structure of the data this points to is:
| Offset | Type | Meaning |
|---|---|---|
| 0x00 | u32 | Maximum VRAM transfer size |
| 0x04 | void * | Pointer to VRAM transfer entries relative to the start of the CEBK block. There will be one entry for each cell in the bank. |
Each VRAM transfer entry takes this structure:
| Offset | Type | Meaning |
|---|---|---|
| 0x00 | u32 | Transfer source address |
| 0x04 | u32 | Transfer Size |
A cell bank may wish to store additional data. This can be placed inside a user extended attributes block in the CEBK block. When present, it takes the form of a sequence of blocks (fully contained within the CEBK block) that take on the same structure as the containing blocks. There is no field indicating the number of blocks, however. The NCER format defines the following block here:
| Offset | Type | Meaning |
|---|---|---|
| 0x00 | u16 | Number of cells |
| 0x02 | u16 | Number of attributes per cell (always 1) |
| 0x04 | void* | Offset to attribute array relative to this struct |
The attribute array consists of one pointer per each cell in the bank. These point to the extended attribute data, which is a single u32 per each cell.
