This format is based on the md2 format but with a few enhanced features. It can be written to using a python export script for the Blender 3D modeling package.
"JOE" is a binary file format in which multi-byte values are expressed with the little-endian byte order. This section details version 3 of the file format.
The following table explicitly defines the various data types used in a JOE file.
| Identifier | Detailed Description |
|---|---|
| int | 32-bit signed integer |
| short | 16-bit signed integer |
| short3 | Three consecutive shorts forming an array |
| float | 32-bit floating-point value. Unsure of the exact format... probably whatever is implemented by x86 machines. |
| float3 | Three consecutive floats forming an array. |
This block of information initiates every file.
| data type | block offset | name | description |
|---|---|---|---|
| int | 0 | magic | 844121161(0x32504449): number used to identify the file as a JOE file. Currently unchecked by vdrift. |
| int | 4 | version | report the file version that this file conforms to. This specification details version 3 of the format. |
| int | 8 | num_faces | every frame is expected to contain the same number of faces (polygons) this value specifies how many. This is currently limited to 32000. |
| int | 12 | num_frames | Presumably, this details the number of frames used in an animation. Currently constrained to "1" |
details a single configuration of a model. "File Header.num_frames" frames follow the file header.
before each frame header, you will find "File Header.num_faces" Face blocks.
| data type | block offset | name | description |
|---|---|---|---|
| int | 0 | num_verts | the number of vertices used in this frame |
| int | 4 | num_textcoords | the number of texture coordinates used in this frame. |
| int | 8 | num_normals | the number of vertex normals used in this frame. |
after each frame header, you will find
- num_verts Vertex blocks
- num_normals Vertex blocks
- num_textcoords Texture Coordinate blocks
Each frame as "File Header.num_faces" face records immediately following the Frame header (decribed above). A face is basically several lists of indices in to vertex, normal, and text coord arrays described in following sections.
For this version, a face is always a triangle ( i.e. a three-vertex polygon ).
| data type | block offset | name | description |
|---|---|---|---|
| short3 | 0 | vertexIndex | Indeces in to the vertex array. These two constructs together define the location of each corner of the face in 3d space. |
| short3 | 6 | normalIndex | Indeces in to the normals array. These two constructs help define how light sources interact with the face at each corner. Normals also help define which side of a face is "front". |
| short3 | 12 | textureIndex | Indeces in to the texture coordinate array. These two constructs together help define which portions of a texture image map to each corner of the face. Note that in the future there may be a multiple of 3 entries in this array to accomidate applying many textures to a single face. Which images are used as textures by a particular model are defined by convention and explained in Car files and formats and Track files and formats |
A vertex block simply contains a three-element float array. Vertex blocks may have a misleading name because they are used for both vertices and normals.
| data type | block offset | name | description |
|---|---|---|---|
| float3 | 0 | vertex | A three-element float array defining the X, Y, and Z components of a vertex at offsets 0, 4, and 8 respectively |
A texture coordinate is a 2-dimensional coordinate used to map prtions of a texture to a model vertex.
| data type | block offset | name | description |
|---|---|---|---|
| float | 0 | u | a value between 0 and 1 indicating a position along the width of the texture |
| float | 4 | v | a value between 0 and 1 indicating a position along the height of the texture. |
Category:Files