Sonic Jam/Models
From Sonic Retro
Models start at $3F908 in MUSEUM.MUS.
Model Format
Models generally consist of the following parts, though there are some exceptions.
Vertices
The first part are vertices, stored as a 3D vector.
Indexing Table
The second part is the indexing table for quads, using the vertices given. Indices are words, and jump by $08. The first vertex would be $0000; the second would be $0008. There's one for each quad.
Vertex Normals
The third, for objects that use Dynamic Gouraud Shading, are the vertex normals. These are normalized 3D vectors. As you'd expect, there's one for each vertex.
Draw Settings
The last for any model is the draw settings. There's one list of settings for each quad. Each list is 16 bytes long. Here's its format:
| Description | Length |
|---|---|
| Unknown. Highest bit seems to turn off backface culling. | Byte |
| Unknown. Bits $1 and $2 affect depth testing in certain instances. | Byte |
| Texture index. $0-$1DB. | Word |
| CMDPMOD command for VDP1. Bit flags. | Word |
| Unknown. | Word |
| Static/Dynamic Gouraud Shading Table Index. | Word |
| CMDCTRL command for VDP1. Bit flags. | Word |
| Unknown. | Word |
| Unknown. | Word |